Integrated circuits with vertically differential superconducting qubit loops and methods to fabricate the same

Abstract

A superconducting circuit and method of fabrication can include at least a portion of a superconducting qubit having high-coherence, low-noise, low susceptibility, which is integrable with other structures and devices of a quantum processor. The superconducting circuit can include: a kinetic inductance layer directly overlying a substrate; a first dielectric layer overlying the kinetic inductance layer; and, a superconductive wiring layer overlying the first dielectric layer. The kinetic inductance layer includes a first qubit conductor of a superconducting qubit loop comprising a superconductive material having a relatively high inductance value, and the superconductive wiring layer includes at least a second qubit conductor to complete the loop, which comprises a superconductive material having a relatively low inductance value. Additional layers can be included to provide: shield structures; a return path between the second and first qubit conductors; galvanic coupling connection interfaces; and, flux bias interfaces with conductors on different layers.

Description

[0001]INTEGRATED CIRCUITS WITH VERTICALLY DIFFERENTIAL SUPERCONDUCTING QUBIT LOOPS AND METHODS TO FABRICATE THE SAME CROSS-REFERENCE TO RELATED APPLICATION This patent application claims priority of U.S. Patent Application No. 63 / 529,840, filed on July 31, 2023, the entire disclosure of which is hereby incorporated by reference herein for all purposes. TECHNICAL FIELD This disclosure generally relates to low-noise superconducting integrated circuits for quantum processors, and, more specifically, to superconducting integrated circuits including vertically differential qubit loops and methods for fabrication thereof. BACKGROUND Superconducting Integrated Circuits Superconductivity is a set of physical properties observed in a material where electrical resistance of the material vanishes and magnetic flux fields are expelled from the material. A material exhibiting these properties is referred to in the present application as a superconductor. A superconductor typically has a characteristic critical temperature below which its electrical resistance drops to zero. A material exhibiting these properties is also referred to in the present application as a superconductive material. A superconductive material may be a superconducting metal, for example. Niobium is a superconducting metal that becomes superconducting below 9.2 K. An electric current in a loop of superconductive material can persist indefinitely with no power source. An integrated circuit (also referred to in the present application as a chip) is one or more electronic circuits on a single piece (or "chip") substrate. In some implementations, the substrate is silicon. In other implementations, the substrate is sapphire. Integration of large numbers of devices on a chip can result in circuits that are orders of magnitude smaller, faster, and less expensive than circuits constructed of discrete electronic components. A superconducting integrated circuit is an integrated circuit that includes superconductive material. A superconducting circuit (e.g., a superconducting integrated circuit) may include one or more superconducting devices. Where the superconducting integrated circuit includes a superconducting quantum processor, a superconducting device of the superconducting integrated circuit may be a superconducting qubit, a coupling device, a readout device, or a flux storage device, for example. Superconducting Processor A quantum processor may take the form of a superconducting processor. However, superconducting processors can include processors that are not intended for quantum computing. For instance, some embodiments of a superconducting processor may not focus on quantum effects such as quantum tunneling, superposition, and entanglement but may rather operate by emphasizing different principles, such as for example the principles that govern the operation of classical computer processors. However, there may still be certain advantages to the implementation of such superconducting “classical” processors. Due to their natural physical properties, superconducting classical processors may be capable of higher switching speeds and shorter computation times than non-superconducting processors, and therefore it may be more practical to solve certain problems on superconducting classical processors. Superconducting Qubits Superconducting qubits are a type of superconducting quantum device that can be included in a superconducting integrated circuit. Superconducting qubits can be separated into several categories depending on the physical property used to encode information. For example, superconducting qubits may be separated into charge, flux and phase devices. Charge devices store and manipulate information in the charge states of the device. Flux devices store and manipulate information in a variable related to the magnetic flux through some part of the device. Phase devices store and manipulate information in a variable related to the difference in superconducting phase between two regions of the device. Superconducting qubits commonly include at least one Josephson junction. A Josephson junction is a small interruption in an otherwise continuous superconducting current path and is typically realized by a thin insulating barrier sandwiched between two superconducting electrodes. Thus, a Josephson junction may be implemented as a three-layer or “tri-layer” structure. Superconducting qubits are further described in, for example, U.S. Patents No. 7,876,248, 8,035,540, and 8,098,179. Quantum Processor A quantum processor may take the form of a superconducting quantum processor. A superconducting quantum processor may include a number of superconducting qubits and associated local bias devices. A superconducting quantum processor may also include couplers (also known as coupling devices or qubit couplers) that selectively provide communicative coupling between qubits. Superconducting qubits are solid state qubits based on circuits of superconductive materials. Operation of superconducting qubits is based on the underlying principles of magnetic flux quantization, and Josephson tunneling. Superconducting effects can be present in different configurations and can give rise to different types of superconducting qubits including flux, phase, charge, and hybrid qubits. The different configurations can vary in the topology of the loops, the placement of the Josephson junctions, and the physical parameters of elements of the superconducting circuits, such as inductance, capacitance, and Josephson junction critical current. In one implementation, the superconducting qubit includes a superconducting loop interrupted by a Josephson junction. The inductance and the critical current may be selected, adjusted, or tuned, to increase the ratio of the inductance of the Josephson junction to the geometric inductance of the superconducting loop, and to cause the qubit to be operable as a bistable device. In some implementations, the ratio of the inductance of the Josephson junction to the geometric inductance of the superconducting loop of a qubit is approximately equal to three. In one implementation, the superconducting coupler includes a superconducting loop interrupted by a Josephson junction. The inductance and the critical current may be selected, adjusted, or tuned, to decrease the ratio of the inductance of the Josephson junction to the geometric inductance of the superconducting loop, and to cause the coupler to be operable as a monostable device. In some implementations, the ratio of the inductance of the Josephson junction to the geometric inductance of the superconducting loop of a coupler is approximately equal to, or less than, one. Further details and embodiments of quantum processors that may be used in conjunction with the present systems and devices are described in, for example, U.S. Patents No.7,533,068; 8,008,942; 8,195,596; 8,190,548; and 8,421,053. Noise in a Quantum Processor A quantum processor may require a local bias to be applied on a qubit to implement a problem Hamiltonian. The local bias applied on the qubit depends on persistent current ^^and external flux bias ^^as described below: ^^^= 2|^^|^^^Noise affects the local bias ^^^in the same way as the external flux bias ^^and thus changes the specification of the qubit terms in the problem Hamiltonian. By altering the problem Hamiltonian, noise may introduce errors into the computational result from quantum annealing. However, this is only one type of misspecification that can result from noise. Noise may also undesirably impact accuracy of coupling of qubits, readout, and other programming of the quantum processor. Low-noise is a desirable characteristic of quantum devices. Noise can compromise or degrade the functionality of the individual devices, such as superconducting qubits, and of the superconducting processor as a whole. For instance, in quantum processors performing quantum annealing, noise can negatively affect qubit coherence, such as by inducing a transition from coherent to incoherent tunneling, and reduce the efficacy of qubit tunneling. Since noise is a serious concern to the operation of quantum processors, measures should be taken to reduce noise wherever possible. Impurities may be deposited on the metal surface and / or may arise from an interaction with the etch / photoresist chemistry and the metal. Noise can be caused by impurities within the components of or on the upper surface of the quantum processor. In some cases, superconducting devices that are susceptible to noise are fabricated in the top wiring layers of a superconducting integrated circuit and are thus sensitive to post-fabrication handling. There is a risk of introducing impurities that cause noise during post-fabrication handling. One approach to reducing noise is using a barrier passivation layer, for example, an insulating layer, to overlie the topmost wiring layer. The use of a barrier passivation layer to minimize noise from impurities on the upper surface of a quantum processor is described in U.S. Patent Application No.2018 / 0219150 (granted as U.S. Patent No.10454015). Noise can also result from an external environment or surrounding circuitry in a superconducting processor. In a quantum processor, flux noise on qubits interferes with properly annealing the quantum processor because of the steep transition between qubit states as the flux bias is swept. Flux noise can be a result of current flowing through wiring of other devices included in the superconducting processor and can have a particularly negative effect on qubits at their respective degeneracy points. For example, flux noise can introduce errors in calculations carried out by the superconducting processor due to inaccuracies in setting flux bias and coupling strength values. Reducing or even eliminating such inaccuracies may be particularly advantageous in using an integrated circuit as part of a quantum processor. A proportion of the static control error can be designed out of the processor with careful layout and high- precision flux sources, as well as by adding circuitry, such as an on-chip shield, to tune away any non-ideal flux qubit behavior. However, in many cases, limitations in integrated circuit fabrication capabilities can make it difficult to address noise by changing processor layout and adding circuitry. There is therefore a general desire for articles and methods to for fabricating integrated circuits that have reduced flux noise (and thus improved coherence) without having to compromise the quantum processor layout by adding additional layers or circuitry. Shielding and Noise Magnetic fields produced by external sources may cause unwanted interactions with devices in the integrated circuit. Accordingly, there may be a need for a superconducting shield proximate to devices populating the integrated circuit to reduce the strength of interference such as magnetic and electrical fields. Superconducting shield layers may be used in single flux quantum (SFQ) or rapid single flux quantum (RSFQ) technology to separate devices from DC power lines that could otherwise undesirably bias the devices. The devices populate the integrated circuit but are separated from the DC power lines by placing a ground plane between the devices and the DC power line. In SFQ circuits, ground planes and shield layers are terminologies used interchangeably. A ground plane in SFQ integrated circuit is a layer of metal that appears to most signals within the circuit as an infinite ground potential. The ground plane helps to reduce noise within the integrated circuit and may be used to ensure that all components within the SFQ integrated circuits have a common potential to compare voltage signals. Contacts can be used between wiring layers and a ground plane throughout SFQ circuitry. Supercurrent flowing in superconducting wires has an associated magnetic field in the same manner as electrons flowing in normal metal wires. Magnetic fields can couple inductively to superconducting wires, inducing currents to flow. Quantum information processing with superconducting integrated circuits necessarily involves supercurrents moving in wires, and hence associated magnetic fields. The quantum properties of quantum devices are very sensitive to noise, and stray magnetic fields in superconducting quantum devices can negatively impact the quantum information processing properties of such circuits. Superconducting ground planes have been used in the art to reduce crosstalk between control lines and devices. However, such approaches have only been used in superconducting integrated circuits for classical processing and sensor applications, which are relatively robust against in-circuit noise and operate at significantly higher temperatures as compared with superconducting quantum processing integrated circuits. In superconducting quantum processing integrated circuits, it is desirable to substantially attenuate and control unwanted crosstalk between devices, otherwise quantum information processing at commercial scales may not be possible. The present methods, systems and apparatus provide techniques for attenuating crosstalk in superconducting quantum processing integrated circuits between quantum devices in order to support the desired quantum effects and controllably couple quantum devices in a manner that permits exchange of coherent quantum information. Kinetic Inductance Current flowing through a metal material in principle stores energy both in the magnetic field of that metal and in the kinetic energy of the charge carriers (e.g., the electrons or Cooper pairs). In non-superconducting metals, the charge carriers collide frequently with the lattice and lose their kinetic energy as Joule heating. This is also referred to as scattering, and quickly releases energy. However, in superconductive materials, scattering is substantially reduced, as the charge carriers are Cooper pairs which are protected against dissipation through scattering. This allows for superconductive materials to store energy in the form of kinetic inductance. This phenomenon allows kinetic inductance to efficiently store energy within the superconducting metal. Kinetic inductance is at least in part determined by the inertial mass of the charge carriers of a given material and increases as carrier density decreases. As the carrier density decreases, a smaller number of carriers must have a proportionally greater velocity in order to produce the same current. Materials that have high kinetic inductance for a given area (as defined below) are referred to as “kinetic inductance materials”, or “high kinetic inductance materials”. Kinetic inductance materials are those that have a high normal-state resistivity and / or a small superconducting energy gap, resulting in a larger kinetic inductance per unit of area. In general, total inductance ^ of a superconductive material is given by ^ = ^^+ ^ீ, where ^ீis the geometric inductance and ^^is the kinetic inductance. The kinetic inductance of a superconducting film in near- zero temperatures is proportional to the effective penetration depth ^^^^. In particular, for a film with a given thickness ^, the kinetic inductance of the film is proportional to the ratio of the length of the film ^ to the width of the film ^, where length is in the direction of the current and width is orthogonal to length (note that both width and length are orthogonal to the dimension in which thickness is measured). That is, ^^~^^^^^ ^for a superconducting film with a given thickness. The kinetic inductance fraction of a material is characterized as ^ = A material considered to have high kinetic inductance would typically have ^ in the range of 0.1 < ^ ^ 1. Materials with less than 10% of the energy stored as kinetic inductance would be considered traditional magnetic storage inductors with a small correction. In some implementations it may be beneficial to attempt to maximize kinetic inductance in minimal volume. This may include attempting to minimize the width of the film, selecting a suitable material with a high effective penetration depth ^^^^, and selecting a length for the film which achieves the desired kinetic inductance. It may also be beneficial to attempt to minimize the thickness ^ of the material, subject to fabrication constraints, as for ^ < 3^^^^(^௨^^)(where ^^^^(^௨^^)is the effective penetration depth of the material in bulk, not thin-film), increases at least approximately proportionately to 1ൗ ^ଶ. In someimplementations, ^ < ^ ή ^^^^(^௨^^), where ^ is some value substantially less than 1 (e.g., 0.5, 0.1, 0.05, 0.01, etc.). Integrated Circuit Fabrication Traditionally, the fabrication of superconducting integrated circuits has not been performed at state-of-the-art semiconductor fabrication facilities. This may be due to the fact that some of the materials used in superconducting integrated circuits can contaminate the semiconductor facilities. For instance, gold may be used as a resistor in superconducting circuits, but gold can contaminate a fabrication tool used to produce CMOS wafers in a semiconductor facility. Consequently, superconducting integrated circuits containing gold are typically not processed by tools which also process CMOS wafers. Superconductor fabrication has typically been performed in research environments where standard industry practices could be optimized for superconducting circuit production. Superconducting integrated circuits are often fabricated with tools that are similar to those traditionally used to fabricate semiconductor chips or integrated circuits. Due to issues unique to superconducting circuits, not all semiconductor processes and techniques are necessarily transferrable to superconductor chip manufacture. Transforming semiconductor processes and techniques for use in superconductor chip and circuit fabrication often requires changes and fine adjustments. Such changes and adjustments typically are not obvious and may require a great deal of experimentation. The semiconductor industry faces problems and issues not necessarily related to the superconducting industry. Likewise, problems and issues that concern the superconducting industry are often of little or no concern in standard semiconductor fabrication. Any impurities within superconducting chips may result in noise which can compromise or degrade the functionality of the individual devices, such as superconducting qubits, and of the superconducting chip as a whole. Since noise is a serious concern to the operation of quantum computers, measures should be taken to reduce dielectric noise wherever possible. The art of integrated circuit fabrication typically involves multiple processes that may be sequenced and / or combined to produce a desired effect. Example systems and methods for superconducting integrated circuit fabrication that may be combined, in whole or in part, with at least some embodiments of the present systems and methods are described in U.S. Patents No.8,951,808 and 9,768,371, which are incorporated herein by reference in their entirety. Etching Etching removes layers of, for example, substrates, dielectric layers, oxide layers, electrically insulating layers and / or metal layers according to desired patterns delineated by photoresists or other masking techniques. Two example etching techniques are wet chemical etching and dry chemical etching. Wet chemical etching or “wet etching” is typically accomplished by submerging a wafer in a corrosive bath such as an acid bath. In general, etching solutions are housed in polypropylene, temperature-controlled baths. The baths are usually equipped with either a ring-type plenum exhaust ventilation or a slotted exhaust at the rear of the etch station. Vertical laminar-flow hoods are typically used to supply uniformly-filtered, particulate-free air to the top surface of the etch baths. Dry chemical etching or “dry etching” is commonly employed due to its ability to better control the etching process and reduce contamination levels. Dry etching effectively etches desired layers through the use of gases, either by chemical reaction such as using a chemically reactive gas or through physical bombardment, such as plasma etching, using, for example, argon atoms. Plasma etching systems have been developed that can effectively etch, for example, silicon, silicon dioxide, silicon nitride, aluminum, tantalum, tantalum compounds, chromium, tungsten, gold, and many other materials. Two types of plasma etching reactor systems are in common use — the barrel reactor system and the parallel plate reactor system. Both reactor types operate on the same principles and vary primarily in configuration only. The typical reactor consists of a vacuum reactor chamber made usually of aluminum, glass, or quartz. A radiofrequency or microwave energy source (referred to collectively as RF energy source) is used to activate fluorine-based or chlorine-based gases which act as etchants. Wafers are loaded into the chamber, a pump evacuates the chamber, and the reactant gas is introduced. The RF energy ionizes the gas and forms the etching plasma, which reacts with the wafers to form volatile products which are pumped away. Physical etching processes employ physical bombardment. For instance, argon gas atoms may be used to physically bombard a layer to be etched, and a vacuum pump system is used to remove dislocated material. Sputter etching is one physical technique involving ion impact and energy transfer. The wafer to be etched is attached to a negative electrode, or “target,” in a glow-discharge circuit. Positive argon ions bombard the wafer surface, resulting in the dislocation of the surface atoms. Power is provided by an RF energy source. Ion beam etching and milling are physical etching processes which use a beam of low-energy ions to dislodge material. The ion beam is extracted from an ionized gas (e.g., argon or argon / oxygen) or plasma, created by an electrical discharge. Reactive ion etching (RIE) is a combination of chemical and physical etching. During RIE, a wafer is placed in a chamber with an atmosphere of chemically reactive gas (e.g., CF4, CCl4, CHF3, and many other gases) at a low pressure. An electrical discharge creates an ion plasma with an energy of a few hundred electron volts. The ions strike the wafer surface vertically, where they react to form volatile species that are removed by the low pressure in-line vacuum system. Planarization The use of chemical-mechanical planarization (CMP) allows for a nearly flat surface to be produced. CMP is a standard process in the semiconductor industry. The CMP process uses an abrasive and corrosive chemical slurry in conjunction with a polishing pad and retaining ring that are pressed together by a dynamic polishing head. This removes material and tends to even out any irregular topography, making the wafer flat or planar. The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings. BRIEF SUMMARY It is advantageous for superconducting qubits used in quantum computing to be highly coherent in order for computation to be performed before quantum information is lost. Coherence of a superconducting qubit can be increased by reducing noise and crosstalk transmitted to the qubit from the environment and other structures within a quantum processor. Integration of superconducting qubits into a strategically ordered multi-layer fabrication stack that includes other devices and structures of the quantum processor can: increase flexibility and control of the superconducting qubits; increase a scale of the quantum processor and complexity of solvable problems; and, reduce exposure of control signals to environment noise. Described herein is a superconducting circuit that includes at least a highly coherent superconducting qubit loop of a superconducting qubit that is integrable with other structures of a quantum processor, and a method of fabricating the superconducting circuit. The superconducting qubit loop can include two qubit loop conductor segments with asymmetric inductance values, enabling control of a proportion of the qubit inductance between a control structure of the qubit and coupler connection interfaces, such that the qubit can galvanically couple to superconducting couplers. Orientation of qubit loop conductor segments within the superconducting circuit can be selected to limit crosstalk between the superconducting qubit loop and structures coupled to the qubit. In an aspect, there is provided a superconducting circuit. The superconducting circuit includes: a substrate; a kinetic inductance layer directly overlying the substrate; a first dielectric layer overlying at least a portion of the kinetic inductance layer; and, a device loop superconductive wiring layer overlying the first dielectric layer. The kinetic inductance layer comprises a material having a relatively high inductance value and exhibiting superconducting behavior at and below a critical temperature. At least a first portion of the kinetic inductance layer is a first device loop conductor segment of a superconducting loop of a body of a superconducting controllable device. The device loop superconductive wiring layer comprises a relatively low inductance superconductive material having a relatively low inductance value and exhibiting superconducting behavior at and below a critical temperature, and the relatively low inductance superconductive material has a low inductance value in comparison to the relatively high inductance value. At least a portion of the device loop superconductive wiring layer is a second device loop conductor segment of the superconducting loop. In some implementations, the superconducting circuit further includes: a second dielectric layer overlying at least a portion of the device loop superconductive wiring layer; and, a shield superconductive wiring layer overlying the second dielectric layer to shield at least the superconducting loop. In some implementations, the superconducting loop of the body of the superconducting controllable device is a superconducting qubit loop of a qubit body of a superconducting qubit. In some implementations, the superconducting qubit loop of the qubit body is galvanically coupled to a Josephson junction of the superconducting qubit. The kinetic inductance layer includes at least one pair of coupler connection leads of the qubit body, and each of the at least one pair of coupler connection leads is located at a distance along a length of the first device loop conductor segment from the Josephson junction such that a majority of a total qubit inductance of the superconducting qubit is arranged therebetween. The superconducting circuit further includes: at least one pair of coupler connection interfaces, each pair of coupler connection interfaces is to galvanically couple a pair of coupler connection leads of the superconducting qubit to a respective pair of coupler leads of a superconducting coupler. In some implementations, the superconducting circuit further includes: a first intermediate superconductive wiring layer directly overlying at least the first dielectric layer; a second dielectric layer overlying at least a portion of the first intermediate superconductive wiring layer; a third dielectric layer overlying at least a portion of the device loop superconductive wiring layer; and, a second intermediate superconductive wiring layer overlying at least a portion of the third dielectric layer. Each pair of coupler connection interfaces includes at least: a pair of first layer coupler connection portions on the first intermediate superconductive wiring layer that directly overlie a respective pair of coupler connection leads; a pair of device loop layer coupler connection portions on the device loop superconductive wiring layer that directly overlie the pair of first layer coupler connection portions; and, a pair of second layer coupler connection portions on the second intermediate superconductive wiring layer that directly overlie the pair of device loop layer coupler connection portions. In some implementations, for each pair of coupler connection interfaces, the pair of second layer coupler connection portions directly galvanically couple to the pair of coupler leads. In some implementations, the superconducting circuit further includes: a fourth dielectric layer overlying at least the second intermediate superconductive wiring layer; and, a third intermediate superconductive wiring layer directly overlying at least the fourth dielectric layer. For each pair of coupler connection interfaces: a first coupler connection interface of the pair of coupler connection interfaces includes a first one of the pair of second layer coupler connection portions that directly galvanically couples to a first coupler lead of the pair of coupler leads; and, a second coupler connection interface of the pair of coupler connection interfaces includes a third layer coupler connection portion on the third intermediate superconductive wiring layer directly overlying a second one of the pair of second layer coupler connection portions, the third layer coupler connection portion directly galvanically coupling to a second coupler lead of the pair of coupler leads. In some implementations, the superconducting circuit further includes: a first intermediate superconductive wiring layer overlying the first dielectric layer; a second dielectric layer directly overlying at least a portion of the first intermediate superconductive wiring layer; a third dielectric layer directly overlying at least a portion of the device loop superconductive wiring layer; a second intermediate superconductive wiring layer directly overlying at least the third dielectric layer; and, a fourth dielectric layer overlying at least the second intermediate superconductive wiring layer. The first intermediate superconductive wiring layer includes one or more first bias loop conductor segments that are located along a cross-section of the superconducting circuit to align with and overlie the first qubit loop conductor segment. The second intermediate superconductive wiring layer includes one or more second bias loop conductor segments, which are each located along the cross-section of the superconducting circuit to align with and overlie a respective one of the first bias loop conductor segments. In some implementations, the body of the superconducting controllable device is symmetrical about a vertical center line along a width of the superconducting circuit. In some implementations, the superconducting circuit further includes: one or more flux bias loops, each flux bias loop surrounding a portion of a length of the second device loop conductor segment; and, an external superconductive wiring layer of the body of the superconducting controllable device comprising at least one pair of bias line interfaces. Each pair of bias line interfaces is directly electrically coupled to a respective flux bias loop. In some implementations, each of the one of more flux bias loops includes: a plurality of superconducting vias that electrically couple a respective pair of bias line interfaces to a respective second bias loop conductor segment; and, a plurality of superconducting vias that electrically couple the respective second bias loop conductor segment to a respective first bias loop conductor segment. In some implementations, each of the one or more flux bias loops includes: a respective first bias loop conductor segment of the one or more first bias loop conductor segments; first bias loop portions of the first intermediate superconductive wiring layer directly overlying the respective first bias loop conductor segment; second bias loop portions of the qubit loop superconductive wiring layer directly overlying the first bias loop portions; a respective second bias loop conductor segment of the one or more second bias loop conductor segments; and, third bias loop portions of the second intermediate superconductive wiring layer directly overlying the respective second bias loop conductor segment and underlying a respective pair of bias line interfaces. In some implementations, each pair of the at least one pair of bias line interfaces is directly electrically couplable to a respective pair of analog lines such that major axes of a first analog line and a second analog line of the respective pair of analog lines are perpendicular to major axes of the first and the second device loop conductor segments. Each pair of analog lines is operable to transmit a respective bias signal to the superconducting loop of the body of the superconducting controllable device. In some implementations, a return path electrically couples the second device loop conductor segment to the kinetic inductance layer. The return path at least partially surrounds the first device loop conductor segment. In some implementations, the return path includes a plurality of superconducting vias that communicatively couple the second device loop conductor segment to the first device loop conductor segment. In some implementations, the kinetic inductance layer includes first and second kinetic inductance layer return path termini located on respective first and second sides of the first device loop conductor segment along a cross-section of the superconducting circuit. The superconducting circuit further comprises: a first intermediate superconductive wiring layer overlying the first dielectric layer and at least a portion of the kinetic inductance layer, and, a second dielectric layer overlying at least a portion of the first intermediate superconductive wiring layer and the first dielectric layer. The device loop superconductive wiring layer overlies the second dielectric layer. The return path comprises first and second intermediate layer return path portions on the first intermediate superconductive wiring layer that directly overlie the first and the second kinetic inductance layer return path termini, and the second device loop conductor segment directly overlies the first and the second intermediate return path portions for communicative coupling of the second device loop conductor segment to the kinetic inductance layer. In some implementations, the superconducting circuit further comprises a shield structure, the shield structure including: a shield superconductive wiring layer on an external surface of the body of the superconducting controllable device in the superconducting circuit; and, first and second shield arms that extend from the shield superconductive wiring layer through the superconducting circuit to the first intermediate superconductive wiring layer to at least partially surround the second device loop conductor segment and the return path. In some implementations, the first and the second shield arms comprise superconducting vias that extend from the shield superconductive wiring layer through the superconducting circuit to the first intermediate superconductive wiring layer. In some implementations, the superconducting circuit further includes a third dielectric layer overlying at least a portion of the device loop superconductive wiring layer, and the shield superconductive wiring layer overlies the third dielectric layer and at least a portion of the device loop superconductive wiring layer. The first and second shield arms include: first and second intermediate layer shield structure portions on the first intermediate superconductive wiring layer, in which the first and the second intermediate layer shield structure portions are each at a respective lateral location along a width of the cross-section of the superconducting circuit; and, first and second device loop layer shield structure portions on the device loop superconductive wiring layer that overlie the first dielectric layer. The shield superconductive wiring layer directly overlies the first and the second device loop layer shield structure portions for communicative coupling of the shield superconductive wiring layer to the first intermediate superconductive wiring layer. In some implementations, the superconducting loop of the body of the superconducting controllable device is galvanically coupled to a Josephson junction of the superconducting controllable device. The kinetic inductance layer includes at least one pair of coupler connection leads of the body of the superconducting controllable device, and each of the at least one pair of coupler connection leads located at a distance along a length of the first device loop conductor segment from the Josephson junction such that a majority of a total inductance of the superconducting controllable device is arranged therebetween. The uperconducting circuit further includes: at least one pair of coupler connection interfaces, each pair of coupler connection interfaces to galvanically couple a pair of coupler connection leads of the superconducting controllable device and a respective pair of coupler leads of a superconducting coupler. In some implementations, the superconducting circuit further includes: a third dielectric layer overlying at least a portion of the device loop superconductive wiring layer; and, a second intermediate superconductive wiring layer overlying at least a portion of the third dielectric layer. Each pair of coupler connection interfaces comprises: a pair of first layer coupler connection portions on the first intermediate superconductive wiring layer that directly overlie a respective pair of coupler connection leads; a pair of device loop layer coupler connection portions on the device loop superconductive wiring layer that directly overlie the pair of first layer coupler connection portions; and, a pair of second layer coupler connection portions on the second intermediate superconductive wiring layer that directly overlie the pair of device loop layer coupler connection portions. In some implementations, for each pair of coupler connection interfaces, the pair of second layer coupler connection portions are directly galvanically couplable to the pair of coupler leads. In some implementations, the superconducting circuit further includes: a fourth dielectric layer overlying at least a portion of the second intermediate superconductive wiring layer; and, a third intermediate superconductive wiring layer overlying at least a portion of the fourth dielectric layer. For each pair of coupler connection interfaces: a first coupler connection interface of the pair of coupler connection interfaces includes a first one of the pair of second layer coupler connection portions that is directly galvanically couplable to a first coupler lead of the pair of coupler leads; and, a second coupler connection interface of the pair of coupler connection Interfaces includes a third layer coupler connection portion on the third intermediate superconductive wiring layer directly overlying a second one of the pair of second layer coupler connection portions, the third layer coupler connection portion directly galvanically couplable to a second coupler lead of the pair of coupler leads. In some implementations, the first intermediate superconductive wiring layer includes one or more first bias loop conductor segments, and the one or more first bias loop conductor segments are located along the cross-section of the superconducting circuit to align with and overlie the first device loop conductor segment. The superconducting circuit further includes: a third dielectric layer overlying at least a portion of the device loop superconductive wiring layer; a second intermediate superconductive wiring layer overlying the third dielectric layer; and, a fourth dielectric layer overlying at least a portion of the second intermediate superconductive wiring layer. The second intermediate superconductive wiring layer comprises one or more second bias loop conductor segments, and each of the one or more second bias loop conductor segments are located along the cross-section of the superconducting circuit to align with and overlie a respective one of the first bias loop conductor segments. In some implementations, the body of the superconducting controllable device is symmetrical about a vertical center line along a width of the superconducting circuit. In some implementations, the superconducting circuit further includes: one or more flux bias loops, each flux bias loop surrounding a portion of a length of the second device loop conductor segment; and, an external superconductive wiring layer of the body of the superconducting controllable device comprising at least one pair of bias line interfaces. Each pair of bias line interfaces is directly electrically coupled to a respective flux bias loop. In some implementations, each of the one or more flux bias loops includes: a plurality of superconducting vias that electrically couple a respective pair of bias line interfaces to a respective second bias loop conductor segment; and, a plurality of superconducting vias that electrically couple the second bias loop conductor segment to a respective first bias loop conductor segment. In some implementations, each of the one or more flux bias loops comprises: a respective first bias loop conductor segment of the one or more first bias loop conductor segments; first bias loop portions of the first intermediate superconductive wiring layer directly overlying the respective first bias loop conductor segment; second bias loop portions of the device loop superconductive wiring layer directly overlying the first bias loop portions; a respective second bias loop conductor segment of the one or more second bias loop conductor segments; and, third bias loop portions of the second intermediate superconductive wiring layer directly overlying the respective second bias loop conductor segment. In some implementations, each pair of the at least one pair of bias line interfaces is directly electrically couplable to a respective pair of analog lines such that major axes of a first analog line and a second analog line of the respective pair of analog lines are perpendicular to major axes of the first and the second device loop conductor segments. Each pair of analog lines is to transmit a respective bias signal to the superconducting loop of the body of the controllable device. In some implementations, the material having a relatively high inductance value is one of: titanium nitride, niobium nitride, niobium titanium nitride, and aluminum nitride. In some implementations, the substrate comprises an electrically insulating material, the electrically insulating material being one of: silicon dioxide, silicon trioxide, silicon nitride, quartz, and sapphire. In some implementations, the relatively low inductance superconductive material comprises one of: aluminum, niobium, and tantalum. In some implementations, the superconducting loop of the body of the superconducting controllable device is a superconducting coupler loop of a coupler body of a superconducting coupler. In some implementations, the superconducting loop of the body of the superconducting controllable device is a superconducting loop of a body of a quantum flex parametron (QFP). In an aspect, there is provided a method of fabricating a superconducting circuit. The method includes: forming a kinetic inductance layer that directly overlies a substrate; forming a first dielectric layer to overlie at least a portion of the kinetic inductance layer; and forming a device loop superconductive wiring layer to overlie the first dielectric layer. The kinetic inductance layer comprises a relatively high inductance superconductive material having a relatively high inductance value and that exhibits superconducting behavior at and below a critical temperature. At least a first portion of the kinetic inductance layer is a first device loop conductor segment of a superconducting loop of a body of a superconducting controllable device. The device loop superconductive wiring layer comprising a relatively low inductance superconductive material, the relatively low inductance superconductive material having a low inductance value relative to the high inductance value and exhibiting superconducting behavior at and below a critical temperature. At least a portion of the device loop superconductive wiring layer is a second device loop conductor segment of the superconducting loop. In some implementations, the forming a kinetic inductance layer includes: depositing the relatively high inductance superconductive material on a surface of the substrate, and patterning the deposited relatively high inductance superconductive material to include at least the first device loop conductor segment of the superconducting loop. The forming a first dielectric layer include at least depositing a dielectric material on a surface of the kinetic inductance layer. The forming a device loop superconductive wiring layer includes: depositing the relatively low inductance superconductive material, and patterning the relatively low inductance superconductive material to include at least the second device loop conductor segment of the superconducting loop. In some implementations, the method further includes: forming a second dielectric layer through deposition of a dielectric material on at least a portion of a surface of the device loop superconductive wiring layer; and, forming a shield superconductive wiring layer through deposition of a layer of the relatively low inductance superconductive material to overlie the second dielectric layer. In some implementations, the forming a kinetic inductance layer that directly overlies a substrate, in which at least a first portion of the kinetic inductance layer is a first device loop conductor segment of a superconducting loop of a body of a superconducting controllable device includes: forming the kinetic inductance layer, in which at least the first portion of the kinetic inductance layer is a first qubit loop conductor segment of a superconducting qubit loop of a qubit body of a superconducting qubit. The forming a device loop superconductive wiring layer to overlie the first dielectric layer, in which at least a portion of the device loop superconductive wiring layer is a second device loop conductor segment of the superconducting loop includes: forming the device loop superconductive wiring layer, in which the device loop superconductive wiring layer is a qubit loop superconductive wiring layer, and at least a portion of the qubit loop superconductive wiring layer is a second qubit loop conductor segment of the qubit superconducting loop. In some implementations, the method further includes: forming a Josephson junction that is galvanically coupled to the superconducting qubit loop of the qubit body, and, forming one or more pairs of coupler connection interfaces. The forming a kinetic inductance layer comprises: depositing the high inductance superconductive material, and patterning the deposited high inductance superconductive material to include the first qubit loop conductor segment and one or more pairs of coupler connection leads of the qubit body. Each of the one or more pairs of coupler connection leads is patterned at a distance along a length of the first qubit loop conductor segment from the Josephson junction such that a majority of a total qubit inductance of the superconducting qubit is arranged therebetween. The one or more pairs of coupler connection interfaces are to galvanically couple a respective pair of coupler connection leads of the qubit body of the superconducting qubit to a respective pair of coupler leads of a superconducting coupler. In some implementations, the method further includes: forming a first intermediate superconductive wiring layer to overlie at least a portion of the first dielectric layer; forming a second dielectric layer to overlie at least a portion of the first intermediate superconductive wiring layer; forming a third dielectric layer to overlie at least a portion of the qubit loop conductor segment superconductive wiring layer; and, forming a second intermediate superconductive wiring layer to overlie at least a portion of the third dielectric layer. To form each of the one or more pairs of coupler connection interfaces: the forming a first intermediate superconductive wiring layer comprises: depositing a second layer of the relatively low inductance superconductive material, and patterning the second layer of the relatively low inductance superconductive material to include a pair of first layer coupler connection portions that directly overlie a respective pair of coupler connection leads; the forming a qubit loop superconductive wiring layer further comprises: patterning the first layer of the relatively low inductance superconductive material to include a pair of qubit loop layer coupler connection portions that directly overlie the pair of first layer coupler connection portions; and, the forming a second intermediate superconductive wiring layer comprises: depositing a third layer of the relatively low inductance superconductive material, and patterning the third layer of the relatively low inductance superconductive material to include a pair of second layer coupler connection portions directly overlying the pair of qubit loop layer coupler connection portions. In some implementations, the patterning the third layer of the relatively low inductance superconductive material to include a pair of second layer coupler connection portions includes: patterning the third layer of the relatively low inductance superconductive material to include the pair of second layer coupler connection portions, in which the second layer coupler connections are directly galvanically couplable to the pair of coupler leads. In some implementations, the method further includes: forming a fourth dielectric layer to overlie at least a portion of the second intermediate superconductive wiring layer; and, forming a third intermediate superconductive wiring layer to overlie at least a portion of the fourth dielectric layer. For each pair of coupler connection interfaces: the patterning the third layer of the relatively low inductance superconductive material to include a pair of second layer coupler connection portions comprises: patterning the third layer of the relatively low inductance superconductive material to include a first one of the pair of second layer coupler connection portions that is directly galvanically couplable to a first coupler lead of the pair of coupler leads; and, the forming a third intermediate superconductive wiring layer comprises depositing a fourth layer of the relatively low inductance superconductive material, and patterning the fourth layer of the relatively low inductance superconductive material to include a third layer coupler connection portion directly overlying a second one of the pair of second layer coupler connection portions, in which the third layer coupler connection portion is directly galvanically couplable to a second coupler lead of the pair of coupler leads. In some implementations, the method further includes: forming a first intermediate superconductive wiring layer to overlie the first dielectric layer, in which the first intermediate superconductive wiring layer includes one or more first bias loop conductor segments; forming a second dielectric layer to overlie at least a portion of the first intermediate superconductive wiring layer; forming a third dielectric layer to overlie at least a portion of the device loop superconductive wiring layer; forming a second intermediate superconductive wiring layer to overlie the third dielectric layer, the forming the second intermediate superconductive wiring layer including forming one or more second bias loop conductor segments; and, forming a fourth dielectric layer to overlie at least a portion of the second intermediate superconductive wiring layer. In some implementations, the forming a first intermediate superconductive wiring layer includes depositing a first layer of the relatively low inductance superconductive material, and patterning the first layer of the relatively low inductance superconductive material to form each of the one or more first bias loop conductor segments at a location along a cross-section of the superconducting circuit that aligns with and overlies the first device loop conductor segment. The forming a second intermediate superconductive wiring layer includes: depositing a second layer of the relatively low inductance superconductive material, and patterning the second layer of the relatively low inductance superconductive material to form each of the one or more second bias loop conductor segments at a location along the cross-section of the superconducting circuit that aligns with and overlies a respective one of the first bias loop conductor segments. In some implementations, the method further includes: forming an external superconductive wiring layer of the body of the superconducting controllable device that includes at least one pair of bias line interfaces; and, forming one or more flux bias loops that include at least a respective first bias loop conductor segment and a respective second bias loop conductor segment, in which each flux bias loop to surround a portion of a length of the second device loop conductor segment. Each pair of bias line interfaces is directly electrically coupled to a respective flux bias loop. In some implementations, forming each of the one or more flux bias loops includes: forming a plurality of superconducting vias to electrically couple a respective pair of bias line interfaces to a respective second bias loop conductor segment; and, forming a plurality of superconducting vias to electrically couple the second bias loop conductor segment to a respective first bias loop conductor segment. In some implementations, to form the each of the one or more flux bias loops: the forming a first intermediate superconductive wiring layer comprises: depositing a first layer of the relatively low inductance superconductive material, and patterning the first layer of the relatively low inductance superconductive material to include: a respective first bias loop conductor segment and first bias loop portions that directly overlie the first bias loop conductor segment. The forming the device loop superconductive wiring layer further comprises: depositing a second layer of the relatively low inductance superconductive material, and patterning the second layer of the relatively low inductance superconductive material to include: the second device loop conductor segment, and second bias loop portions that directly overlie the first bias loop portions. The forming a second intermediate superconductive wiring layer further comprises: depositing a third layer of the relatively low inductance superconductive material, and patterning the third layer of the relatively low inductance superconductive material to include: a respective second bias loop conductor segment, and third bias loop portions that directly overlie the respective second bias loop conductor segment and underlie a respective pair of bias line interfaces. In some implementations, the method further includes forming a return path that electrically couples the second device loop conductor segment of the superconducting loop to the kinetic inductance layer. The return path has a relatively low inductance value and at least partially surrounds the first device loop conductor segment. In some implementations, the forming the return path comprises forming a plurality of superconducting vias to communicatively couple the second device loop conductor segment to the first device loop conductor segment. In some implementations, the forming a kinetic inductance layer includes: depositing the relatively high inductance superconductive material, and patterning the relatively high inductance superconductive material to include: the first device loop conductor segment, and first and second kinetic inductance layer return path termini on respective first and second sides of the first device loop conductor segment along a cross-section of the superconducting circuit. The method further includes: forming a first intermediate superconductive wiring layer, including deposition of a first layer of the relatively low inductance superconductive material, and patterning the first layer of the relatively low inductance superconductive material to include first and second intermediate layer return path portions that respectively directly overlie the first and the second kinetic inductance layer return path termini, and, forming a second dielectric layer overlying at least a portion of the first intermediate superconductive wiring layer, wherein the device loop superconductive wiring layer overlies the second dielectric layer. The forming a device loop superconductive wiring layer includes: depositing a second layer of the relatively low inductance superconductive material, and patterning the second layer of the relatively low inductance superconductive material to include the second device loop conductor segment. The second device loop conductor segment directly overlies the first and the second intermediate return path portions. In some implementations, the method further includes forming a shield structure, including: forming a shield superconductive wiring layer on an external surface of the body of the superconducting controllable device in the superconducting circuit; and, forming first and second shield arms that at least partially surround the second device loop conductor segment and the return path. In some implementations, the forming first and second shield arms comprises forming superconducting vias that extend from the shield superconductive wiring layer through the superconducting circuit to the first intermediate superconductive wiring layer. In some implementations, the method further includes forming a third dielectric layer overlying at least a portion of the of the device loop superconductive wiring layer. To form the first and the second shield arms: the forming a first intermediate superconductive wiring layer further comprises patterning the first layer of the relatively low inductance superconductive material to include first and second intermediate layer shield structure portions, each at a respective lateral location along a width of the cross-section of the superconducting circuit; the forming a device loop superconductive wiring layer further comprises patterning the second layer of the relatively low inductance superconductive material to include first and second device loop layer shield structure portions that respectively directly overlie the first and the second intermediate layer shield structure portions; and, the forming a shield superconductive wiring layer comprises depositing a shield layer of the relatively low inductance superconductive material that directly overlies at least the first and the second device loop layer shield structure portions. In some implementations, the method further includes: forming a Josephson junction that is galvanically coupled to the superconducting loop of the body of the superconducting controllable device, and forming one or more pairs of coupler connection interfaces. The forming a kinetic inductance layer further includes patterning the high inductance superconductive material to include one or more pairs of coupler connection leads of the body of the superconducting controllable device, each of the one or more pairs of coupler connection leads patterned on the kinetic inductance layer at a distance along a length of the first device loop conductor segment from the Josephson junction such that a majority of a total inductance of the superconducting controllable device is arranged therebetween. The one or more pairs of coupler connection interfaces are to galvanically couple a respective pair of coupler connection leads of the body of the superconducting controllable device to a respective pair of coupler leads of a superconducting coupler. In some implementations, the method further includes: forming a fourth dielectric layer to overlie at least a portion of the device loop superconductive wiring layer; and, forming a second intermediate superconductive wiring layer to overlie at least a portion of the fourth dielectric layer. To form each of the one or more pairs of coupler connection interfaces: the forming a first intermediate superconductive wiring layer comprises: depositing a second layer of the relatively low inductance superconductive material, and patterning the second layer of the relatively low inductance superconductive material to include a pair of first layer coupler connection portions that directly overlie a respective pair of coupler connection leads; the forming a device loop superconductive wiring layer further comprises: patterning the first layer of relatively low inductance superconductive material to include a pair of device loop layer coupler connection portions that directly overlie the pair of first layer coupler connection portions; and, the forming a second intermediate superconductive wiring layer comprises: depositing a third layer of the relatively low inductance superconductive material, and patterning the third layer of the relatively low inductance superconductive material to include a pair of second layer coupler connection portions directly overlying the pair of device loop layer coupler connection portions. In some implementations, the patterning the third layer of the relatively low inductance superconductive material to include a pair of second layer coupler connection portions comprises patterning the third layer of the relatively low inductance superconductive material to include a pair of second layer coupler connection portions that are directly galvanically couplable to the pair of coupler leads. In some implementations, the method further includes: forming a fourth dielectric layer to overlie at least a portion of the second intermediate superconductive wiring layer; and, forming a third intermediate superconductive wiring layer to overlie at least a portion of the fourth dielectric layer. To form each of the one or more pairs of coupler connection interfaces: the patterning the third layer of the relatively low inductance superconductive material to include a pair of second layer coupler connection portions comprises patterning the third layer of the relatively low inductance superconductive material to include a first one of the pair of second layer coupler connection portions that is directly galvanically couplable to a first coupler lead of the pair of coupler leads; and, the forming a third intermediate superconductive wiring layer comprises depositing a fourth layer of the relatively low inductance superconductive material, and patterning the fourth layer of the low relatively inductance superconductive material to include a third layer coupler connection portion directly overlying a second one of the pair of second layer coupler connection portions, wherein the third layer coupler connection portion directly galvanically couplable to a second coupler lead of the pair of coupler leads. In some implementations, the forming a first intermediate superconductive wiring layer further comprises patterning the first layer of the relatively low inductance superconductive material to include one or more first bias interface loop conductor segments, and each of the one or more first bias loop conductor segments at a location along a cross-section of the superconducting circuit that aligns with and overlies the first device loop conductor segment. The method further includes: forming a second intermediate superconductive wiring layer to overlie the third dielectric layer, including: deposition of a third layer of the relatively low inductance superconductive material, and patterning the third layer of the relatively low inductance superconductive material to include one or more second bias loop conductor segments, in which each of the one or more second bias loop conductor segments is patterned at a location along the cross-section of the superconducting circuit that aligns with and overlies a respective one of the first bias loop conductor segments; and, forming a fourth dielectric layer to overlie at least a portion of the second intermediate superconductive wiring layer. In some implementations, the method further includes: forming an external superconductive wiring layer of the body of the superconductive controllable device that includes at least one pair of bias line interfaces; and, forming one or more flux bias loops that include at least a respective first bias loop conductor segment and a respective second bias loop conductor segment, each flux bias loop to surround a portion of a length of the second device loop conductor segment. Each pair of bias line interfaces is directly galvanically coupled to a respective flux bias loop. In some implementations, forming each of the one or more flux bias loops includes: forming a plurality of superconducting vias to electrically couple a respective pair of bias line interfaces to a respective second bias loop conductor segment; and, forming a plurality of superconducting vias to electrically couple the second bias loop conductor segment to a respective first bias loop conductor segment. In some implementations, to form the each of the one or more flux bias loops: the forming a first intermediate superconductive wiring layer further comprises patterning the first layer of the relatively low inductance superconductive material to include: a respective first bias loop conductor segment and first bias loop portions that directly overlie the first bias loop conductor segment; the forming a device loop superconductive wiring layer further comprises patterning the second layer of the relatively low inductance superconductive material to include second bias loop portions that directly overlie the first bias loop portions; and, the forming a second intermediate superconductive wiring layer further comprises patterning the third layer of the relatively low inductance superconductive material to include: a respective second bias loop conductor segment, and third bias loop portions that directly overlie the respective second bias loop conductor segment and underlie a respective pair of bias line interfaces. In some implementations, the forming a kinetic inductance layer includes forming the kinetic inductance layer from one of: titanium nitride, niobium nitride, niobium titanium nitride, and aluminum nitride. In some implementations, the forming a superconductive loop layer comprises forming the superconductive wiring layer from one of: aluminum, niobium, and tantalum. In some implementations, the forming a kinetic inductance layer that directly overlies a substrate, in which at least a first portion of the kinetic inductance layer is a first device loop conductor segment of a superconducting loop of a body of a superconducting controllable device includes: forming the kinetic inductance layer, in which at least the first portion of the kinetic inductance layer is a first coupler loop conductor segment of a superconducting coupler loop of a coupler body of a superconducting coupler. The forming a loop superconductive wiring layer to overlie the first dielectric layer, in which at least a portion of the loop superconductive wiring layer is a second device loop conductor segment of the superconducting loop includes: forming the device loop superconductive wiring layer, in which at least a portion of the coupler loop superconductive wiring layer is a second coupler loop conductor segment of the coupler superconducting loop. In some implementations, the forming a kinetic inductance layer that directly overlies a substrate, in which at least a first portion of the kinetic inductance layer is a first device loop conductor segment of a superconducting loop of a body of a superconducting controllable device includes: forming the kinetic inductance layer, in which the first loop conductor segment is a portion of a superconducting body loop of a quantum flux parametron (QFP). The forming a loop superconductive wiring layer to overlie the first dielectric layer, in which at least a portion of the loop superconductive wiring layer is a second device loop conductor segment of the superconducting loop includes: forming the device loop superconductive wiring layer, in which the second device loop conductor segment is a second portion of the superconducting body loop of the QFP. In an aspect, there is provided a superconducting qubit. The superconducting qubit includes a qubit body comprising a superconducting qubit loop that includes a first qubit loop conductor segment communicatively coupled to a second qubit loop conductor segment. The first qubit loop conductor segment comprises a relatively high inductance superconductive material that has a relatively high inductance value and exhibits superconducting behavior at and below a critical temperature, and the second qubit loop conductor segment comprises a relatively low inductance superconductive material that has a relatively low inductance value in comparison to the relatively high inductance value of the relatively high inductance superconductive material and exhibits superconducting behavior at and below a critical temperature. The second qubit loop conductor segment overlies the first qubit loop conductor segment within at least a portion of a superconducting circuit that comprises the superconducting qubit. The superconducting qubit includes a Josephson junction electrically coupled to the superconducting qubit loop of the qubit body. In some implementations, the qubit body further comprises a shield structure that at least partially surrounds the superconducting qubit loop, and includes at least a planar shield portion on an external surface of the qubit body that overlies the second qubit loop conductor segment in the at least a portion of the superconducting circuit. The planar shield portion comprising the relatively low inductance superconductive material. In some implementations, the shield structure further comprises a pair of shield arms, and each one of the pair of shield arms extends from the planar shield portion into the at least a portion of the superconducting circuit to at least partially surround the second qubit loop conductor segment. The shield arms comprise the relatively low inductance superconductive material. In some implementations, the qubit body further includes a return path extending from the second qubit loop conductor segment to return path termini. The return path termini comprise the relatively high inductance superconductive material and are located on a same layer of the at least a portion of the superconducting circuit as the first qubit loop conductor segment such that the return path at least partially surrounds the first qubit loop conductor segment. At least a majority of the return path comprises the relatively low inductance superconductive material. In some implementations, the first qubit loop conductor segment comprises one or more pairs of coupler connection leads; and, the qubit body further comprises one or more pairs of coupler connection interfaces. Each of the one or more pairs of coupler connection interfaces is configured to galvanically couple a pair of the one or more pair of coupler connection leads to a respective pair of coupler leads of a superconducting coupler. In some implementations, each one of the one or more pairs of coupler connection leads is located at a distance along a length of the qubit body from the Josephson junction such that a majority of a total qubit inductance of the superconducting qubit is arranged therebetween. In some implementations, each one of the one or more pairs of coupler connection interfaces of the qubit body includes a first coupler connection interface and a second coupler connection interface. The first and second coupler connection interface respectively extend through the at least a portion of the superconducting circuit from a first and a second coupler connection lead of a respective pair of coupler connection leads to a first and a second coupler connection site of the qubit body. The first and the second coupler connection site are located on a same layer of the at least a portion of the superconducting circuit that overlies the second qubit loop conductor segment. The first and the second coupler connection interface comprise the relatively low inductance superconductive material. In some implementations, each one of the one or more pairs of coupler connection interfaces includes a first coupler connection interface that extends through the at least a portion of the superconducting circuit from a first coupler connection lead of a respective pair of coupler connection leads to a first coupler connection site of the qubit body at which the first coupler connection interface is galvanically couplable to a first coupler lead of a respective pair of coupler leads. The first coupler connection site overlies the second qubit loop conductor segment. Each one of the one or more pairs of coupler connection interfaces includes a second coupler connection interface that extends through the at least a portion of the superconducting circuit from a second coupler connection lead of the pair of coupler connection leads to a second coupler connection site of the qubit body at which the second coupler connection interface is galvanically couplable to a second coupler lead of the pair of coupler leads. The second coupler connection site overlies the first coupler connection site. The first and the second coupler connection interface comprise the relatively low inductance superconductive material. In some implementations, the qubit body further includes one or more bias connection interfaces, and each bias connection interface is to electrically couple the superconducting qubit loop to a respective pair of analog lines that transmit a bias signal. Each bias connection interface includes: a first bias loop conductor segment that interposes the first qubit loop conductor segment and the second qubit loop conductor segment, and the first bias loop conductor segment is aligned with the first qubit loop conductor segment along a width of the at least a portion of the superconducting circuit; and, a second bias loop conductor segment that overlies the second qubit loop conductor segment, and the second bias loop conductor segment is aligned with the first bias loop conductor segment along the width of the at least a portion of the superconducting circuit. In some implementations, each one of the one or more bias connection interfaces includes a pair of bias line interfaces on an external surface of the qubit body in the superconducting circuit that overlies the second qubit loop conductor segment, in which the pair of bias line interfaces are directly electrically couplable to a respective pair of analog lines. Each one of the one or more bias connection interfaces includes a flux bias loop of the qubit body that surrounds a portion of a length of the second qubit loop conductor segment. The flux bias loop includes the first and the second bias loop conductor segment, and the flux bias loop galvanically couples the first bias loop conductor segment, the second bias loop conductor segment, and the pair of bias line interfaces. The pair of bias line interfaces and the flux bias loop comprise the relatively low inductance superconductive material. In some implementations, the pair of bias line interfaces are directly communicatively couplable to a respective pair of analog lines such that major axes of first and the second analog lines of the respective pair of analog lines are perpendicular to major axes of the first and the second qubit loop conductor segments. In some implementations, the external surface of the qubit body in the at least a portion of the superconducting circuit further includes at least a portion of a shield structure. The shield structure comprising the relatively low inductance superconductive material. In some implementations, the superconducting qubit is symmetrical about a vertical center line along a width of the qubit body. In some implementations, the relatively high inductance superconductive material comprises one of: titanium nitride, niobium nitride, niobium titanium nitride, and aluminum nitride. In some implementations, the relatively low inductance superconductive material comprises one or more of: aluminum, niobium, and tantalum. In some implementations, an inductance per unit length of the relatively high inductance superconductive material is 50 times greater than an inductance per unit length of the relatively low inductance superconductive material. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS In the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not necessarily drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn, are not necessarily intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the drawings. FIG.1 is a schematic diagram of a hybrid computing system including a digital computer coupled to an analog computer, in accordance to the present disclosure. FIG.2 is a schematic diagram of a circuit of an example superconducting quantum processor, according to the present disclosure. FIG.3 is a schematic view of a portion of multi-layer fabrication stack of an example implementation of a superconducting integrated circuit, according to the present disclosure. FIG.4 is a top plan view of a qubit, according to the present disclosure. FIGs 5A, 5B, 5C, 5D, 5E, 5F, and 5G are cross-sectional views of a superconducting integrated circuit including vertically differential qubit loop conductor segments at successive stages of fabrication, according to the present disclosure. FIGs 6A, 6B, 6C, 6D, 6E, 6F, 6G, 6H, 6I, and 6J are cross-sectional views of an alternative superconducting integrated circuit including vertically differential qubit loop conductor segments at successive stages of fabrication, according to the present disclosure. FIG.7A is a cross-sectional view of a portion of a superconducting integrated circuit including vertically differential qubit loop conductor segments and vertically differential flux bias lines, according to the present disclosure. FIG.7B is a cross-sectional view of a portion of an alternative superconducting integrated circuit including vertically differential qubit loop conductor segments and vertically differential flux bias lines, according to the present disclosure. FIG.8A is a plan view of a portion of a superconducting integrated circuit including vertically differential qubit loop conductor segments and a bias line interface, according to the present disclosure. FIG.8B is a cross-sectional view of the superconducting integrated circuit of FIG.8A, according to the present disclosure. FIG.9A is a plan view of a portion of a superconducting integrated circuit including vertically differential qubit loop conductor segments and a coupler connection interface at one stage of fabrication, according to the present disclosure. FIG.9B is a plan view of the superconducting integrated circuit of FIG.9A at a later stage of fabrication, according to the present disclosure. FIG.9C is a cross-sectional view of the superconducting integrated circuit of FIG.9B, according to the present disclosure. FIG.9D is a plan view of the superconducting integrated circuit of FIG.9A at an alternative later stage of fabrication, according to the present disclosure. FIG.9E is a cross-sectional view of the superconducting integrated circuit of FIG.9D, according to the present disclosure. FIG.10 is a flowchart illustrating a method to fabricate a superconducting circuit including vertically differential qubit loop conductor segments, according to the present disclosure. DETAILED DESCRIPTION Preamble In the following description, some specific details are included to provide a thorough understanding of various disclosed implementations and embodiments. One skilled in the relevant art, however, will recognize that embodiments may be practiced without one or more of these specific details, or with other methods, components, materials, etc. In other instances, well-known structures associated with superconductive devices, integrated superconductive circuits, and fabrication equipment, have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the implementations or embodiments of the present methods. Throughout this specification and the appended claims, the words “element” and “elements” are used to encompass, but are not limited to, all such structures, systems, and devices associated with superconductive circuits and integrated superconductive circuits. Unless the context requires otherwise, throughout the specification and claims which follow, the word “comprise” is synonymous with “including,” and is inclusive or open-ended (i.e., does not exclude additional, unrecited elements or acts). Reference throughout this specification to “one embodiment” “an embodiment”, “another embodiment”, “one example”, “an example”, “another example”, “one implementation”, “another implementation”, or the like means that a particular referent feature, structure, or characteristic described in connection with the embodiment, example, or implementation is included in at least one embodiment, example, or implementation. Thus, the appearances of the phrases “in one embodiment”, “in an embodiment”, “another embodiment” or the like in various places throughout this specification are not necessarily all referring to the same embodiment, example, or implementation. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments, examples, or implementations. It36should be noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to a circuit including “a device” includes a single device, or two or more devices. It should also be noted that the term “or” is generally employed in its sense including “and / or” unless the content clearly dictates otherwise. In the descriptions of the superconducting circuits herein, the term “layer” can herein refer to a material having a thickness, where at least a portion of the material is in contact with at least a portion of an additional surface. In some implementations, at least a portion of a layer may fill in gaps between portions of a preceding layer (for instance, due to patterning of the preceding layer). Thus, while referred to as layers, two or more denominated layers can reside on a same level or plane or a common level or common plane spaced along a cross- section of a superconducting circuit. In the descriptions of the superconducting circuits herein, the terms: “overlie” and “overlying” refer to a layer either directly or indirectly overlying a referenced layer. The term “directly overlying” a referenced layer refers to the layer being formed directly on at least a portion of the referenced layer without an intervening layer. The term “indirectly overlying” a layer refers to the layer being formed over at least a portion of the referenced layer, with at least one intervening layer between the referenced layer and the layer. While such assumes a particular orientation of the superconducting circuits, this is not intended to be limiting. Thus, the orientations of the superconducting as illustrated in the figures can be flipped upside down, for example. Herein, “galvanic” coupling can refer to electrical coupling in which the coupled structures and / or devices share a common length of metal, and “direct galvanic coupling” can refer to galvanic coupling for which there are no interleaving metal layers between the coupled structures and / or devices. The headings provided herein are for convenience only and do not interpret the scope or meaning of the embodiments. Example Computing System FIG.1 illustrates a computing system 100 comprising a digital computer 102. The example digital computer 102 includes one or more digital processors 106 that may be used to perform classical digital processing tasks. Digital computer 102 may further include at least one system memory 122, and at least one system bus 120 that couples various system components, including system memory 122 to digital processor(s) 106. System memory 122 may store one or more sets of processor-executable instructions, which may be referred to as modules 124. The digital processor(s) 106 may be any logic processing unit or circuitry (for example, integrated circuits), such as one or more central processing units ("CPUs"), graphics processing units ("GPUs"), digital signal processors ("DSPs"), application-specific integrated circuits ("ASICs"), programmable gate arrays ("FPGAs"), programmable logic controllers (“PLCs”), etc., and / or combinations of the same. The digital processor(s) 106 can be operated at room temperatures, or cooled below room temperatures, or even cooled and operated at cryogenic temperatures. In some implementations, computing system 100 comprises a quantum computer 104, which may include one or more quantum processors 126. Quantum processor 126 may include at least one superconducting integrated circuit fabricated using systems and methods described in the present application. Digital computer 102 may communicate with quantum computer 104 via, for instance, a controller 118. Certain computations may be performed by quantum computer 104 at the instruction of digital computer 102, as described in greater detail herein. Digital computer 102 may include a user input / output subsystem 108. In some implementations, the user input / output subsystem includes one or more user input / output components such as a display 110, mouse 112, and / or keyboard 114. System bus 120 may employ any known bus structures or architectures, including a memory bus with a memory controller, a peripheral bus, and a local bus. System memory 122 may include non-volatile memory, such as read-only memory ("ROM"), static random-access memory (“SRAM”), Flash NAND; and volatile memory such as random-access memory ("RAM"). Digital computer 102 may also include other non-transitory computer- or processor-readable storage media or non-volatile memory 116. Non-volatile memory 116 may take a variety of forms, including: a hard disk drive for reading from and writing to a hard disk (for example, a magnetic disk), an optical disk drive for reading from and writing to removable optical disks, and / or a solid state drive (SSD) for reading from and writing to solid state media (for example NAND- based Flash memory). Non-volatile memory 116 may communicate with digital processor(s) via system bus 120 and may include appropriate interfaces or controllers 118 coupled to system bus 120. Non-volatile memory 116 may serve as long-term storage for processor- or computer-readable instructions, data structures, or other data (sometimes called program modules or modules 124) for digital computer 102. Although digital computer 102 has been described as employing hard disks, optical disks and / or solid-state storage media, those skilled in the relevant art will appreciate that other types of non-transitory and non-volatile computer- readable media may be employed. Those skilled in the relevant art will appreciate that some computer architectures employ non-transitory volatile memory and non-transitory non-volatile memory. For example, data in volatile memory may be cached to non-volatile memory, or a solid-state disk that employs integrated circuits to provide non-volatile memory. Various processor-readable or computer-readable and / or executable instructions, data structures, or other data may be stored in system memory 122. For example, system memory 122 may store executable instructions to provide communications with remote clients and scheduling use of resources including resources on the digital computer 102 and quantum computer 104. Also, for example, system memory 122 may store at least one of processor executable instructions or data that, when executed by at least one processor, causes the at least one processor to execute the various algorithms to execute instructions. In some implementations system memory 122 may store processor- or computer- readable calculation instructions and / or data to perform pre-processing, co- processing, and post-processing to quantum computer 104. System memory 122 may store a set of analog computer interface instructions to interact with quantum computer 104. Quantum computer 104 may include at least one analog processor such as quantum processor 126. Quantum computer 104 may be provided in an isolated environment, for example, in an isolated environment that shields the internal elements of the quantum computer from heat, magnetic field, and other external noise. The isolated environment may include a refrigerator, for instance a dilution refrigerator, operable to cryogenically cool the analog processor, for example to temperature below approximately 1 K. Quantum computer 104 may include programmable elements such as qubits, couplers, and other superconductive on-chip devices (also referred to herein as controllable devices). Qubits may be read out via readout control system 128. Readout results may be sent to other computer- or processor- readable instructions of digital computer 102. Qubits may be controlled via a qubit control system 130. Qubit control system 130 may include on-chip Digital to Analog Converters (DACs) and analog lines that are operable to apply a bias to a target device. Couplers that couple qubits may be controlled via a coupler control system 132. Coupler control system 132 may include tuning elements such as on-chip DACs and analog lines. In some implementations, qubit control system 130 and coupler control system 132 may be used to implement a quantum annealing schedule as described herein on quantum computer 104 employing one or more quantum processors. In accordance with some implementations of the present disclosure, a quantum processor, such as quantum processor 126, may be designed to perform quantum annealing and / or adiabatic quantum computation. Examples of quantum processors are described in U.S. Patent No.7,533,068. Alternatively, a quantum processor, such as quantum processor 126, may be a universal quantum computer, and qubit control system 130 and coupler control system 132 may be used to perform universal adiabatic quantum computing, or other forms of quantum computation such as gate model-based quantum computation. Programmable elements may be included in quantum processor 126 in the form of one or more integrated circuits. Qubits and couplers may be positioned in layers of the integrated circuit that comprise a first material. Other devices, such as devices comprising readout control system 128, may be positioned in other layers of the integrated circuit that comprise a second material. The programmable elements and / or devices of the quantum processor can advantageously include the various superconducting integrated circuit arrangements with high coherence devices as described herein. Superconducting Quantum Processor FIG.2 is a schematic diagram of a circuit 200 of a portion of an example superconducting quantum processor, according to at least one implementation. In some implementations, the superconducting quantum processor of circuit 200 may be quantum computer 104 shown in FIG.1. Circuit 200 includes two qubits 201 and 202. Also shown is a tunable coupling (diagonal coupling) via coupler 210 between qubits 201 and 202 (i.e., providing 2-local interaction). While circuit 200 shown in FIG.2 includes only two qubits 201, 202 and one coupler 210, those of skill in the art will appreciate that a superconducting quantum processor may include any number of qubits and any number of couplers coupling information between them. Circuit 200 includes a plurality of interfaces 221, 222, 223, 224, and 225 that are used to configure and control the state of the superconducting quantum processor. Each of interfaces 221, 222, 223, 224, and 225 may be realized by a respective inductive coupling structure, as illustrated, as part of a programming subsystem and / or an optional evolution subsystem. Alternatively, or in addition, interfaces 221, 222, 223, 224, and 225 may be realized by a galvanic coupling structure. In some implementations, one or more of interfaces 221, 222, 223, 224, and 225 may be driven by one or more flux storage devices or Digital-to- Analog Converters (DACs). Such a programming subsystem and / or optional evolution subsystem may be separate from the superconducting quantum processor, or may be included locally (i.e., on-chip with the superconducting quantum processor). For example, referring to computing system 100 of FIG.1, locally included programming subsystem and / or optional evolution subsystem can be arranged as part of quantum computer 104. In the operation of the superconducting quantum processor, interfaces 221 and 224 may each be used to couple a flux signal into a respective compound Josephson junction (CJJ) 231 and 232, respectively, of qubits 201 and 202. Similarly, interfaces 222 and 223 may each be used to apply a flux signal into respective superconducting loops 226 and 227 of qubits 201 and 202. Furthermore, interface 225 may be used to couple a flux signal into coupler 210. Throughout this specification and the appended claims, the term “quantum processor” is used to generally describe a collection of physical qubits (e.g., qubits 201 and 202) and qubit couplers (e.g., coupler 210). The physical qubits 201 and 202 and the coupler 210 are referred to as the “controllable devices” of a quantum processor and their corresponding parameters are referred to as the “controllable parameters” of the quantum processor. In the context of a quantum processor, the term “programming subsystem” is used to generally describe the interfaces (e.g., “programming interfaces” 222, 223, and 225) used to apply the controllable parameters to the controllable devices of the superconducting quantum processor, including at least qubits 201, 202 and coupler 210, and other associated control circuitry. In some implementations, programming interfaces 222, 223, and 225 may include DACs, which can be used to control controllable devices such as qubits, couplers, and parameter tuning devices. As previously described, the programming interfaces of the programming subsystem may communicate with other subsystems which may be separate from the quantum processor or may be included locally on the processor, such as arranged as part of quantum computer 104 of FIG.1. The programming subsystem may be operable to receive programming instructions in a machine language of the quantum processor and execute the programming instructions to program the programmable and controllable devices (e.g., at least qubits 201, 202 and coupler 210) in accordance with the programming instructions. In some implementations, where the quantum processor is implemented as quantum computer 104 of FIG.1, the controllable devices (e.g., qubits 201, 202 and coupler 210) may be arranged as part of quantum processor 126 and these other subsystems may be at least one of: readout control system 128, qubit control system 130, and coupler control system 132 of quantum computer 104. The initial programming instructions may be provided using digital computer 102 and sent to the quantum processor and its corresponding subsystems through digital processor(s) 106 or controller(s) 118. Circuit 200 also includes readout devices 251 and 252, where readout device 251 is associated with qubit 201 and readout device 252 is associated with qubit 202. In the example implementation shown in FIG.2, each of readout devices 251 and 252 includes a direct current superconducting quantum interference device (DC-SQUID) inductively coupled to the corresponding qubit. In some implementations, each of readout devices 251 and 252 can include at least a controllable storage device that is superconductive at and below a critical temperature and arranged on-chip, and which can store qubit state information. More particularly, each of readout devices 251 and 252 can be a quantum flux parametron (QFP) as shown in FIG.2, which each comprise a superconducting loop interrupted by a respective CJJ. Readout devices 251, 252 can be implemented as described in one or more of: US Patents No.6,627,916; 8,169,231; 10,938,346; and, 11,424,521 and / or US Patent Application Publication No.2022 / 0207404, which are incorporated by reference herein. In the context of circuit 200, the term “readout subsystem” is used to generally describe the readout devices 251, 252 used to read out the final states of the qubits (e.g., qubits 201 and 202) in the superconducting quantum processor to produce a bit string. The readout subsystem may also include other elements, such as routing circuitry (e.g., latching elements, a shift register, or a multiplexer circuit) and / or may be arranged in alternative configurations (e.g., an XY-addressable array, an XYZ-addressable array, etc.), any of which may comprise DACs. One implementation of a qubit readout is described in U.S. Patent No.8,854,074. The behavior of the readout subsystem may be informed by signals transmitted from readout control system 128 in FIG.1. Readout control system 128 may be coupled to readout devices 251 and 252 via DACs, analog lines, or other suitable means. While FIG.2 illustrates only two physical qubits 201, 202, one coupler 210, and two readout devices 251, 252, a quantum processor (e.g., processor comprising circuit 200) may employ any number of qubits, couplers, and / or readout devices, including a larger number (e.g., hundreds, thousands or more) of qubits, couplers and / or readout devices. The application of the teachings herein to processors with a different (e.g., larger) number of computational components should be readily apparent to those of ordinary skill in the art. A superconducting quantum processor may include other types of qubits besides superconducting flux qubits. For example, a superconducting quantum processor may include superconducting charge qubits, transmon qubits, and the like. In some implementations, circuit 200 of the superconducting processor can optionally be all or a portion of a superconducting processor used for quantum annealing and / or adiabatic quantum computing. In such implementations, plurality of interfaces 221, 222, 223, 224, and 225 couple respective flux signals into qubits 201, 202 to realize parameters of the system Hamiltonian. For instance, the coupling of interfaces 221, 224 to qubits 201, 202 may provide a tunable tunneling term (the ο^term), and the coupling may provide the off-diagonal ^௫terms of the system Hamiltonian. The use of interfaces 222, 223 to apply a flux signal into superconducting loops 226, 227 of qubits 201, 202 may realize the terms (dimensionless local fields for the qubits), and the coupling may provide the diagonal ^௭terms in the system Hamiltonian. Lastly, interface 225 may be used to couple a flux signal into coupler 210, thereby realizing the ^^^term(s) (dimensionless local fields for the couplers), for which the coupling may provide the diagonal ^^௭^^௭terms in the system Hamiltonian. Examples of Hamiltonians (and their terms) used in quantum computing are described in greater detail in, for example, U.S. Patent No.9,424,526. In such implementations, parameters of the system Hamiltonian may be considered “controllable parameters” of the quantum processor. In implementations where circuit is all or a portion of a superconducting processor used for quantum annealing and / or adiabatic quantum computing, the example superconducting quantum processor may include an evolution subsystem comprising “evolution interfaces” 221 and 224 used to evolve devices such as qubits 201, 202 and other associated control circuitry and / or instructions. For example, the evolution subsystem may include annealing signal lines and their corresponding interfaces (221, 224) to the qubits (201, 202). In other implementations, circuit 200 of the superconducting processor can optionally be all or a portion of a superconducting processor used for gate-model quantum computing. In some implementations, first and second qubits 201, 202 may be fluxonium qubits. In some implementations where circuit 200 is part of a superconducting processor used for gate-model quantum computing, fluxonium qubits can be arranged in a multi-layer fabrication stack that allows multiplexed control circuitry to be built therearound. Fluxonium qubits can be advantageously designed to have a large inductance through use of a kinetic inductor as part of a superconducting loop of the qubit. FIG.3 is a schematic diagram of an example superconducting qubit 300. Superconducting qubit 300 comprises a superconducting loop 302 and a Josephson junction structure 304. At least a portion of superconducting loop 302 comprises a kinetic inductor 302a. In the present example implementation, Josephson junction structure 304 comprises a first and a second Josephson junction 306a and 306b to form a compound Josephson junction (CJJ). First Josephson junction 306a is in series with a first inductor 308a, and a second Josephson junction 306b is in series with a second inductor 308b. A person skilled in the art will understand that Josephson junction structure 304 may include only one Josephson junction or include compound-compound Josephson junctions (CCJJ) and in certain implementations first and second inductors 308a, 308b might not be present. In some implementations, kinetic inductor 302a comprises one of: niobium nitride (NbN), niobium titanium nitride (NbTiN), titanium nitride (TiN), aluminum nitride (AlN), and granular aluminum. Kinetic inductor 302a may be included within a fabrication stack directly adjacent or proximate to a low-noise substrate, and Josephson junction structure 304 may be included at a layer distal to kinetic inductor 302a to improve coherence of superconducting qubit 300. In one example implementation, kinetic inductor 302a may have an inductance of 5 nH. A detailed description of a superconducting qubit with a kinetic inductance can be found in International Patent Application Publication WO2022178130. Superconducting Qubit with Vertically Differential Qubit Loop Conductor Segments Coherence exists when there is a definite phase relation between different states of qubits within a quantum processor, and allows for computation of quantum information encoded in the quantum states of qubits. When the qubits interact with their environment, this quantum information may be lost as a result of the qubits decohering in a thermodynamically irreversible manner following a decoherence time. In implementations in which the quantum processor performs computations using adiabatic quantum computing and / or quantum annealing, decoherence may cause tunneling to become decoherent before a change in state is induced by intrinsic phase transitions. This decoherence may limit the speed and / or accuracy with which the processor evolves and produces solutions. In implementations in which the quantum processor performs gate model computation, long decoherence times may be particularly advantageous due to the time scales of computations using sequences of logical gates acting upon the qubits. Decoherence times can also be interchangeable with “coherence times”, which are durations of time during which the quantum processor remains coherent. Gate-model quantum computing typically includes a series of quantum error correction operations. Quantum error correction requires the qubits to be capable of maintaining quantum coherence over time periods on the order of 1,000 times the single-gate time. Short decoherence times may prevent the quantum processor from performing all desired computations before quantum information is lost. To mitigate degradation of quantum information, it is desirable for qubits of a quantum processor to have high coherence with a long decoherence time, low noise, and low crosstalk among qubits and between qubits and other devices. A rate at which qubits decohere can be increased by exposure to charge noise in layers of Josephson junctions of a superconducting processor fabrication stack, and flux noise originating in dielectric layers that is transmitted to junction layers across dielectric–metal interfaces. Replacement of dielectric materials with rare, low-noise and low-loss dielectrics may be expensive and technically challenging due to sensitivity of the junction fabrication process to perturbations. Increasing qubit inductance can reduce an amount of noise seen by the qubits. In part, this may be achieved using fluxonium qubits, and more particularly, using superconducting qubits having kinetic inductors, such as superconducting qubit 300 of FIG.3. The fabrication of high-coherence qubits has been demonstrated by patterning a single layer of low-loss superconducting metal including qubit circuitry on top of a low-noise, low-loss substrate. For example, a qubit may be arranged to directly overlie a sapphire wafer. The lack of coupling interfaces and use of low-loss materials in the resulting circuit may greatly reduce noise affecting the qubit behavior and qubit interaction with its environment, both of which would reduce coherence of the qubit. However, the resulting single layer circuit may also have limited functionality. With only one layer of low-noise superconducting metal and a low-noise substrate, the quantum processor might not have the resources available to contain, program, and readout a number of qubits and couplers that can be used to represent variables and relationships between variables of problems to be solved thereon. Such a quantum processor might not be scalable and capable of solving complex problems. A complexity of problems that can be solved on a quantum processor, such as quantum processor 126 or quantum processor of circuit 200 of FIG.2, may be proportional to its number of qubits, couplers, and associated devices. Therefore, a quantum processor for solving complex problems can ideally be scaled to accommodate a large number of devices. To address size and scalability concerns, it may be advantageous to implement a superconducting circuit including a quantum processor using a multi- layer fabrication stack. A multi-layer fabrication stack enables on-chip integration of control structures, such as readout control system 128, qubit control system 130, and coupler control system 132, with qubits of a quantum processor, such as quantum processor 126. On-chip inclusion of these structures may allow for at least one or more of: parameter tuning of controllable devices; improvements in speed and / or accuracy of read-out and addressing of controllable devices due to proximity of circuit elements; improvements in structures to control qubits, couplers, and other programmable devices due to decreased noise; and, shielding to prevent degradation of signals transmitted between components within the superconducting circuit. Use of a multi-layer fabrication stack may reduce degradation of signals transmitted between qubits and other structures of the quantum processor due to transmission of signals across internal wiring that is not exposed to the external environment, and shorter travel distances. Resultantly, less environmental noise may be introduced to the signals that might interfere with operation of the quantum processor. To reduce exposure of qubits and couplers to potential sources of noise, the layers of a multi-layer fabrication stack of a superconducting circuit may be strategically ordered based on the noise susceptibility of devices formed in the respective layers. For example, the qubits and couplers may be arranged in a low-noise wiring region that is adjacent to a low-noise substrate, and dielectric layers and control circuitry may be arranged in a region further from the substrate. Multi-layered fabrication stacks having wiring layers of different superconductive materials are further described in International Patent Application Publication WO2022178130. In some example implementations, qubits may include a kinetic inductor, such as kinetic inductor 302a of superconducting qubit 300, as a noise reduction measure. A majority of the superconducting loops of the qubits may comprise a material having a high inductance value, such as titanium nitride (TiN), in a kinetic inductance layer of the fabrication stack. In some implementations, superconducting loops of qubits within the multi-layer fabrication stack can each include two conductors in the kinetic inductance layer. At least some electric field energy within a superconducting integrated circuit can be contained in dielectric layers of the fabrication stack, including in a substrate. In a superconducting circuit comprising at least a qubit body, one can calculate a proportion of the electric field energy between a pair of qubit loop conductor segments that is contained within each dielectric layer based on the material properties of the layer. It can be advantageous to arrange qubit loop conductor segments in a kinetic inductance layer adjacent to the substrate and for a greater proportion of the electric field energy to be contained in the substrate relative to other dielectric layers to reduce an amount of charge noise seen by the qubit body. Herein, a “conductor” can refer to a conductive line, wire, or trace that carries a signal. A portion of a conductor of a superconducting qubit loop (also referred to herein as a “qubit loop conductor segment”) can be a superconductive line, wire, or trace that forms at least a portion of a superconducting qubit loop. In implementations in which a superconducting qubit loop includes more than one conductor segments, the conductors segments are communicatively coupled to one another to form the closed body loop of the qubit. For instance, superconducting loop 302 of superconducting qubit 300 (i.e., the body loop) can be implemented in a fabrication stack by one or more qubit loop conductor segments. In instances in which there is more than one qubit loop conductor segment, the qubit loop conductor segments can be electrically coupled across one or more of: an inductive interface, a magnetic interface, or a galvanic interface to provide the closed superconducting loop 302 of FIG.3. In implementations in which superconducting loops of qubits within the multi-layer fabrication include two conductors in the kinetic inductance layer, all of superconducting loop 302, including kinetic inductor 302a, can be two communicatively coupled superconductive lines, wires, or traces that comprise a material having a high kinetic inductance value. In FIG.3, broken line boxes are included to show two qubit loop conductor segments of superconducting loop 302. First qubit loop conductor segment 303a can comprise a portion of superconducting loop 302 provided by kinetic inductor 302a and second qubit loop conductor segment 303b can comprise the remaining portion of superconducting loop 302 (excluding Josephson junction structure 304). However, this arrangement is only an example and is not intended to be limiting. Superconducting loop 302 can be realized by any number of qubit loop conductor segments that form a closed loop, which can be arranged in any manner with respect to Josephson junction structure 304. One technique to mitigate some of the noise of dielectric–metal interfaces on the qubits can include implementation of a quantum processor having a flip- chip configuration. The quantum processor may include: an individually fabricated main chip including qubits and couplers adjacent to a low-noise substrate, and an individually fabricated flip chip including other structures and devices of the quantum processor. The external layers of the two superconducting circuits are arranged in communication with one another across an air gap or a vacuum layer therebetween. In some implementations, quantum processors having flip-chip configurations can include qubits such as superconducting qubit 300 that can each include two qubit loop conductor segments in a same layer of the fabrication stack. For instance, in an implementation of superconducting qubit 300 as a fabrication stack, a single layer can include two qubit loop conductor segments that make up superconducting loop 302. First qubit loop conductor segment 303a on the single layer can comprise a superconductive material with a high kinetic inductance value, which can provide kinetic inductor 302a in the circuit diagram of FIG.3. Second qubit loop conductor segment 303b on the single layer can comprise a superconductive material with a low inductance value relative to an inductance value of the material having a high kinetic inductance value (also herein a material having a relatively high inductance value), which can provide the remainder of superconducting loop 302 in the circuit diagram of FIG.3. In some implementations, electrical connections may be made using bump bonds between the main chip having qubits and couplers and the flip chip having control circuitry. Footprints and crosstalk associated with the bump-bunds may limit processor scalability and qubit density, which may reduce operating speed to a speed slower than a decoherence time of the qubits. In other implementations, the qubits and couplers of the main chip are electrically coupled to control circuitry on the flip chip inductively and / or magnetically, such that there is no physically direct electrical communication between the chips. For further detail regarding quantum processors having flip- chip configurations, see International Patent Application WO2024102504. Although electrical and / or magnetic shields can be included in the fabrication stacks, the inductive communication interfaces between devices of the main and flip chips may be prone to undesirably large amounts of crosstalk that may adversely affect processor operation. Some of the crosstalk to which a qubit is susceptible can be communications between other devices, including other qubits, or communication between different interfaces and the qubit itself. For instance, superconducting loop 226 of qubit 201 (FIG.2) is coupled to: interface 222 to bias superconducting loop 226, coupler 210 across an interface, and readout device 251 across an interface. In some implementations, a superconducting loop of a qubit may be coupled to additional structures across additional interfaces; for example, a qubit may be coupled to more than one coupler. Crosstalk between various interfaces of a superconducting loop of a qubit can be reduced by arranging lines coupled thereto to be perpendicular to major axes of the two qubit loop conductor segments in the fabrication stack, as discussed in further detail below. As previously noted, crosstalk can also be reduced by formation of a large portion of the superconducting loop from a material having a high kinetic inductance value; however, a high kinetic inductance value can also reduce desired signal transmission between the qubit and a coupler. To provide a sufficient coupling strength, galvanic interfaces between the qubit and couplers can be used to replace inductive interfaces. Design of the qubit should increase impedance between control structures and qubit loop conductor segments to reduce problems arising from uncontrolled superconducting loops. Uncontrolled superconducting loops can refer to superconducting loops formed by unintentional galvanic, magnetic, and / or inductive coupling between structures within the qubit and / or between structures in the qubit and structures, lines, and / or devices in proximity to the qubit. Therefore, there exists a need for a superconducting circuit comprising qubits having high coherence, low noise, and low susceptibility to crosstalk, which can readily be integrated into a quantum processor including other control circuitry. To achieve this, a superconducting loop of a qubit can be fabricated to comprise two qubit loop conductor segments arranged in different layers of a multi-layer fabrication stack. A first qubit loop conductor segment can be arranged in a kinetic inductance layer directly adjacent to a low-noise substrate, and a second qubit loop conductor segment can be arranged in a superconductive wiring layer elsewhere in the stack. This arrangement may be referred to herein as a qubit with “vertically differential” qubit loop conductor segments. Major axes of vertically differential qubit loop conductor segments can be arranged perpendicularly to lines coupled to interfaces that are either vertically differential or horizontally differential (i.e., conductor segments in a same layer) for reduced crosstalk, and the different material composition of the qubit loop conductor segments can support galvanic coupling. FIG.4 is a top plan view of a qubit 400. The plane of top view of qubit 400 may herein be referred to as the X—Y plane, in accordance with a set of axes. Qubit 400 is in a multi-layer fabrication stack, and layers of the multi-layer fabrication stack are described in detail later herein. Qubit 400 includes a qubit body 402 and a Josephson junction 404. Qubit body 402 includes four coupler connection interfaces 406a, 406b, 406c, and 406d that are located longitudinally along qubit body 402 from Josephson junction 404. Qubit body 402 also includes: five bias connection interfaces 408a, 408b, 408c, 408d, 408e that are located along qubit body 402; bias connection interfaces 408a, 408b, 408c, 408d positioned between Josephson junction 404 and coupler connection interfaces 406a, 406b; and, bias connection interface 408e positioned between Josephson junction 404 and coupler connection interfaces 406c and 406d. In some implementations, qubit 400 is one of a plurality of qubits in quantum processor 126 of computing system 100 of FIG.1. In some implementations, qubit 400 is one of qubits 201, 202 of circuit 200 of FIG.2 and qubit body 402 is respectively one of superconducting loops 226, 227. In some implementations, qubit 400 can be superconducting qubit 300 of FIG.3, and qubit body 402 can include superconducting loop 302. Although not visible in FIG.4, qubit body 402 extends across a plurality of layers of a multi-layer fabrication stack. In some implementations, the superconducting qubit loop of qubit body 402 includes vertically differential qubit loop conductor segments, such that there is a first qubit loop conductor segment in the kinetic inductance layer and a second qubit loop conductor segment in a superconductive wiring layer at another location in the multi-layer fabrication stack. For instance, in implementations in which qubit 400 is superconducting qubit 300, the first qubit loop conductor segment can be first qubit loop conductor segment 303a provided by kinetic inductor 302a of superconducting loop 302 as a superconductive line, lead, or wire in a kinetic inductance layer of the multi-layer fabrication stack. The second qubit loop conductor segment can be second qubit loop conductor segment 303b provided by a remainder of superconducting loop as a superconductive line, lead, or wire in a relatively low inductance superconductive wiring layer of the multi-layer fabrication stack. As FIG.4 is a top view, a shield layer 402a of qubit body 402 can be seen. Shield layer 402a can be an external layer of qubit body 402 in a multi-layer fabrication stack, and can shield other structures and devices of qubit body 402 on underlying layers from undesirable electrical and / or magnetic fields. For example, shield layer 402a can shield at least a portion of one of more of: a superconducting qubit loop, coupler connection interfaces 406a, 406b, 406c, 406d, and bias connection interfaces 408a, 408b, 408c, 408d, 408e of qubit body 402 to reduce an amount of noise transmitted thereto and improving quality of operation. Josephson junction 404 can be a compound Josephson junction (CJJ) or a compound-compound Josephson junction (CCJJ), which is a CJJ in which at least one of the parallel paths is itself a CJJ. In implementations in which qubit 400 is superconducting qubit 300, Josephson junction 404 can be Josephson junction structure 304. In implementations where qubit 400 is one of first and second qubits 201, 202, Josephson junction 404 can be a respective one of first and second CJJ 231 or 232. At each one of coupler connection interfaces 406a, 406b, 406c, and 406d, qubit 400 can couple to a respective coupler. In implementations in which qubit 400 is one of first and second qubits 201, 202, a coupler connection interface (one of 406a, 406b, 406c, and 406d) can be an interface at which the one of qubits 201 and 202 couples to coupler 210. Each of coupler connection interfaces 406a, 406b, 406c, and 406d provide galvanic coupling between qubit body 402 of qubit 400 and a respective coupler of a plurality of couplers. Although four coupler connection interfaces 406a, 406b, 406c, and 406d are shown in FIG.4, this is not intended to be limiting, and qubit 400 can include any suitable number of coupler connection interfaces in accordance with an architecture of a quantum processor. Bias connection interfaces 408a, 408b, 408c, 408d, 408e each respectively couple qubit body 402 to a bias signal source. In an example, a bias signal source may be a digital-to-analog converter (DAC) of a quantum processor that generates a bias signal based on a control signal transmitted from a digital computer, such as digital computer 102 of computing system 100 (FIG.1). In implementations in which qubit 400 is one of qubits 201 and 202, a bias line interface (one of 406a, 406b, 406c, and 406d) can be an interface at which the one of first and second qubits 201, 202 couples to a respective one of interface 222 or interface 223. Bias connection interfaces 408a, 408b, 408c, 408d, 408e can each be galvanically coupled to analog lines that carry respective flux bias signals. In some implementations, each bias connection interface (408a, 408b, 408c, 408d, 408e) can include two conductors, which can be configured as vertically differential conductor segments or portions or horizontally differential conductor segments or portions. FIGs 5A, 5B, 5C, 5D, 5E, 5F, and 5G are cross-sectional views in the X— Z plane of a superconducting circuit at successive stages of fabrication. A last shown fabrication stage shown of the superconducting circuit (i.e., superconducting circuit 500g shown in FIG.5G) includes a superconducting loop of a superconducting qubit with vertically differential qubit loop conductor segments. The circuit of superconducting circuit 500g can be a qubit body, such as qubit body 402 of qubit 400 in FIG.4, and FIG.5G can be a cross-sectional view of the X—Z plane of a portion of qubit body 402. In some implementations, superconducting circuit 500g can include superconducting loops 226, 227 and the interfaces shown to interrupt superconducting loops 226, 227 of qubits 201, 202 of FIG.2 and / or superconducting loop 302 of superconducting qubit 300 of FIG.3. FIG.5A illustrates a superconducting circuit 500a at a first stage of fabrication. Superconducting circuit 500a includes a substrate 502 and a kinetic inductance layer 504 overlying substrate 502. Kinetic inductance layer 504 can be deposited to overlie some or all of a surface of substrate 502. In some implementations, kinetic inductance layer 504 directly overlies substrate 502. In alternative implementations, other layers may interpose substrate 502 and kinetic inductance layer 504. Substrate 502 comprises a low-noise electrically insulating material. In some implementations, the electrically insulating material of substrate 502 comprises one of: sapphire, quartz, silicon trioxide (SiO3), silicon dioxide (SiO2), and silicon nitride (SiN). It is to be understood that substrate 502 is not required to be a wafer comprised of a single material. In some implementations, substrate 502 can comprise a wafer and a low-noise electrically insulating material disposed or grown on the surface of the wafer. Kinetic inductance layer 504 can be formed of a superconductive material having a high kinetic inductance value, which, in some implementations, can comprise one of: titanium nitride (TiN), niobium nitride (NbN), niobium titanium nitride (NiTiN), aluminum nitride (AlN), and granular aluminum. The material having a high kinetic inductance value can also have a relatively high inductance value in comparison to other materials of superconducting circuit 500g due at least to its ability to store a high amount of energy in the form of kinetic energy, and, in some cases, to store a high amount of energy in its magnetic field. The superconductive material having the high kinetic inductance value can exhibit superconducting behavior at and below a critical temperature. At least a portion of kinetic inductance layer 504 can include a first qubit loop conductor segment having vertically differential qubit loop conductor segments. In some implementations, kinetic inductance layer 504 can form kinetic inductor 302a of superconducting qubit 300 (FIG.3). FIG.5B illustrates a superconducting circuit 500b at a stage of fabrication that follows the fabrication stage shown in FIG.5A. Superconducting circuit 500b also includes kinetic inductance layer 504 overlying substrate 502 of superconducting circuit 500a; however, in superconducting circuit 500b, kinetic inductance layer 504 has been patterned such that kinetic inductance layer 504 only overlies a portion of substrate 502, in which at least a portion of the kinetic inductance layer 504 forms or comprises a first qubit loop conductor segment 504a. The arrangement of first qubit loop conductor segment 504a to directly overlie substrate 502 limits the exposure of the first qubit loop conductor segment 504a to environmental noise and charge noise formed at dielectric—metal interfaces of the fabrication stack. In some implementations, first qubit loop conductor segment 504a can make up a large portion of a superconducting loop of the qubit, and a majority of an inductance of the qubit. Formation of first qubit loop conductor segment 504a of material having a high kinetic inductance value, and therefore a high inductance value, may reduce noise and crosstalk by increasing an impedance of the superconducting loop, thereby limiting signal transmission. The material of first qubit loop conductor segment 504a can also exhibit superconducting behavior at and below a critical temperature. FIG.5C illustrates a superconducting circuit 500c at a stage of fabrication that follows the fabrication stage shown in FIG.5B. Superconducting circuit 500c includes patterned kinetic inductance layer 504 overlying substrate 502, and also includes a first dielectric layer 506. First dielectric layer is deposited to entirely overlie kinetic inductance layer 504, and to fill in the region where the material having a high kinetic inductance value has been etched away to overlie a portion of substrate 502. In some implementations, dielectric layer 506 can be comprised of silicon dioxide (SiO2) or silicon nitride (SiN). FIG.5D illustrates a superconducting circuit 500d at a stage of fabrication that follows the fabrication stage shown in FIG.5C. Superconducting circuit 500d includes: first dielectric layer 506 overlying patterned kinetic inductance layer 504, which overlies substrate 502. Superconducting circuit 500d also includes a first superconductive wiring layer 508 that directly overlies all of first dielectric layer 506. First superconductive wiring layer 508 can be comprised of a material that exhibits superconducting behavior at and below a critical temperature. The material of first superconductive wiring layer 508 can be a material having a low kinetic inductance value and a low inductance value relative to the material having a high kinetic inductance value and a high inductance value of kinetic inductance layer 504. Herein, a material with a low kinetic inductance value can refer to a material in which less than 10% of the energy therewithin is stored as kinetic inductance. Herein, a material with a relatively low inductance value can refer to a material that is able to store only a small amount of energy in the form of kinetic energy and in its magnetic field with respect to the material with a relatively high inductance value. In some implementations, an inductance per unit length of the material having a relatively high inductance value can be approximately 50 times larger than an inductance per unit length of the material having a relatively low inductance value. In some implementations, the material of first superconductive wiring layer 508 can be a metal such as: aluminum, niobium, tantalum, and any other metal having suitable superconducting characteristics. FIG.5E illustrates a superconducting circuit 500e at a stage of fabrication that follows the fabrication stage shown in FIG.5D. Superconducting circuit 500e includes: first superconductive wiring layer 508, first dielectric layer 506, kinetic inductance layer 504, and substrate 502 of superconducting circuit 500d. However, at this fabrication stage, first superconductive wiring layer 508 has been patterned. In some implementations, like that illustrated in FIG.5E, first superconductive wiring layer 508 is etched such that the remaining portion (a second qubit loop conductor segment 508a) of first superconductive wiring layer 508 at least partially, and preferably completely, overlies patterned kinetic inductance layer 504 in a horizontal dimension (i.e., an X-dimension) of the cross-section of superconducting circuit 500e. Thus, the remaining portion (second qubit loop conductor segment 508a) can preferably have a profile that matches in shape and dimensions a profile of patterned kinetic inductance layer 504 (first qubit loop conductor segment 504a), and can be in registration with the same. At least a portion of patterned first superconductive wiring layer 508 includes the second qubit loop conductor segment 508a of the qubit having vertically differential qubit loop conductor segments. As first qubit loop conductor segment 504a is arranged as part of kinetic inductance layer 504, the two qubit loop conductor segments (504a, 508a) are located on different vertical layers of the multi-layer fabrication stack, and can be used to differentiate electric field energy seen at the two qubit loop conductor segments 504a, 508a across first dielectric layer 506. FIG.5F illustrates a superconducting circuit 500f at a stage of fabrication that follows the fabrication stage shown in FIG.5E. Superconducting circuit 500f includes: patterned first superconductive wiring layer 508, first dielectric layer 506, kinetic inductance layer 504, and substrate 502 of superconducting circuit 500e. Superconducting circuit 500f also includes a second dielectric layer 510 that is deposited to overlie first superconductive wiring layer 508 and at least a portion of first dielectric layer 506. Second dielectric layer 510 can comprise a same or different dielectric material than the material of first dielectric layer 506, and can comprise silicon dioxide (SiO2) or silicon nitride (SiN). FIG.5G illustrates a superconducting circuit 500g at a stage of fabrication that follows the fabrication stage shown in FIG.5F. Superconducting circuit 500g comprises all of the elements of superconducting circuit 500f (i.e., patterned first superconductive wiring layer 508, first dielectric layer 506, kinetic inductance layer 504, and substrate 502), and also includes a second superconductive wiring layer 512 that overlies second dielectric layer 510. Second superconductive wiring layer 512 can comprise a same or different relatively low inductance superconductive material as first superconductive wiring layer 508, and can for example comprise one of: aluminum, niobium, and tantalum. In some implementations, second superconductive wiring layer 512 is a shield layer. A shield layer may indirectly or directly extend along and cover at least one surface of one or more superconducting device, one or more superconducting metal layer, or a portion of one or more thereof to provide electrical and / or magnetic shielding. The shield layer may reduce crosstalk and noise between devices or signals carried by superconducting layers of the multi- layer fabrication stack. Further information on superconducting shields for use in a superconducting circuit can be found in U.S. Patent No.7,687,938. In superconducting circuit 500g, second superconductive wiring layer 512 can be shield layer 402a of qubit body 402, which can at least partially shield the superconducting qubit loop of qubit body 402 that includes at least a portion of kinetic inductance layer 504 and first superconductive wiring layer 508. Although only one qubit is illustrated as part of superconducting circuit 500g, it is to be understood that a superconducting circuit can include any number of vertically differential qubits and other structures including but not limited to: couplers, bias interfaces, and control structures such as DACs and superconducting quantum interference devices (SQUIDs). As well, it is to be understood that a fabrication stack of such a superconducting circuit can include any suitable number of layers, and can include more layers than are shown in FIG.5G. For instance, a superconducting circuit can include additional superconductive wiring layers, additional dielectric layers, and additional kinetic inductance layers. In some implementations, groups of additional layers can form regions within the fabrication stack that, for instance, form a specific control circuit. Arrangement of first qubit loop conductor segment 504a on kinetic inductance layer 504 directly adjacent to substrate 502 beneficially limits an amount of charge noise transmitted to first qubit loop conductor segment 504a across the material interface between the two layers. This is due to the low-noise and low-loss material properties of substrate 502, enabling substrate 502 to maintain a portion of the electric field energy in superconducting circuit 500g without leaking into other layers and / or the environment. Although placement of first qubit loop conductor segment 504a in kinetic inductance layer 504 makes it such that first qubit loop conductor segment 504a has a desirably relatively high inductance value that can advantageously limit crosstalk with other devices and / or structures, this arrangement may also reduce efficacy of desired communication therebetween. Here, placement of second qubit loop conductor segment 508a at a vertically different location within the multi-layer fabrication stack places second qubit loop conductor segment 508a in first superconductive wiring layer 508, which comprises a different material than first qubit loop conductor segment 504a. In contrast to first qubit loop conductor segment 504a, second qubit loop conductor segment 508a comprises a material having a relatively low inductance value. The relatively lower inductance value of first superconductive wiring layer 508 that includes second qubit loop conductor segment 508a can be leveraged for effective communication with Josephson junction 404 of qubit 400 (FIG.4) or a CJJ of the qubit. Herein, the difference in inductance values of the two qubit loop conductor segments may be referred to as “asymmetric”. Asymmetric qubit loop conductor segment inductance values enable a portion of the superconducting qubit loop having relatively high inductance to be arranged between a control structure of the qubit and interfaces at which the superconducting qubit loop connects to couplers, such as coupler connection interfaces 406a, 406b, 406c, 406d of qubit 400 (FIG.4). The portion of the superconducting qubit loop having relatively high inductance accordingly has a relatively high impedance per unit of length, which advantageously reduces undesired crosstalk between the Josephson junction and the coupler. However, the kinetic inductance material of this portion of the superconducting qubit loop does not generate a magnetic field having sufficient strength to support magnetic coupling between itself and one or more couplers. The vertically differential qubit loop conductor segment arrangement of superconducting circuit 500g provides a portion of the superconducting qubit loop having a relatively low inductance between the interfaces at which the superconducting qubit loop connects to the couplers. This supports galvanic coupling between the superconducting qubit loop and one or more couplers. Galvanic coupling can be more efficient than magnetic coupling, and qubit control issues associated with galvanic coupling of multiple superconducting loops are mitigated due to the arrangement of the relatively high inductance portion of the superconducting qubit loop relative to the coupling interfaces. As superconducting qubits have a bandwidth of operation, a qubit, including its superconducting qubit loop, must have a frequency within this range. Consequently, there is an overall inductance budget when designing the qubit to meet this criterion. The superconducting qubit loop of superconducting circuit 500g having asymmetric qubit loop conductor segments can be designed to realize the advantages of materials having a high kinetic inductance value without exceeding the inductance budget and without impairing operation of the qubit due to the relatively low inductance value of a portion of the superconducting loop. Superconducting circuits that include a superconducting loop of a qubit having vertically differential qubit loop conductor segments can advantageously increase design flexibility of an integrated quantum processor circuit, as there are more ways in which superconducting lines of other structures and / or devices within the quantum processor can be communicatively coupled to a qubit therein without further increasing crosstalk. Arrangement of these other lines to be perpendicular to major axes of the qubit loop conductor segments, such as first and second device loop conductor segments on kinetic inductance layer 504 and first superconductive wiring layer 508 respectively, significantly limits undesired crosstalk between the lines and qubit loop conductor segments. In configurations in which the qubit loop conductor segments are vertically differential, each pair of additional superconducting lines can be either horizontally differential (i.e., both lines coupled or couplable to the superconducting circuit via interfaces arranged on a same layer thereof, which can be any layer comprising superconducting material described above or an additional interleaving or overlying layer comprising superconducting material) or vertically differential (i.e., a first and second analog line are coupled to the superconducting circuit via respective first and second interfaces, and the first interface and the second interface are arranged on different layers of the superconducting circuit) while still being perpendicular to the major axes of the qubit loop conductor segments. Conversely, in superconducting circuits in which the qubit loop conductor segments are horizontally differential, only vertically differential pairs of additional superconducting lines can be perpendicular to the major axes of qubit loop conductor segments due to geometry of the arrangement. While several aspects of the design of superconducting circuit 500g reduce an amount of crosstalk affecting its superconducting qubit loop, the vertically differential qubit loop conductor segment configuration may be more susceptible to charge noise than a superconducting qubit loop having a horizontally differential qubit loop conductor segment configuration that has all qubit loop conductor segments on a layer of a fabrication stack adjacent to the substrate. In a multi-layer fabrication stack having a vertically differential qubit loop conductor segment configuration, dielectric layers (e.g., first dielectric layer 506) are interposed between layers including the qubit loop conductor segments(e.g., kinetic inductance layer 504 and first superconductive wiring layer 508). A large portion of electric field energy in the fabrication stack may be undesirably pulled out from the substrate into the relatively lossy and noisy dielectric layers. Subsequently, there may be a greater dissipation of electric field energy from the dielectric layers into the layers including the qubit loop conductor segments. In order to mitigate the effects of noise on the superconducting qubit loop from the dielectric layers of a qubit having a vertically differential qubit loop conductor segment configuration, a superconducting circuit can include a return path between a second qubit loop conductor segment and a layer of the fabrication stack that includes the first qubit loop conductor segment. A return path can advantageously redirect a portion of the electric field energy back to the low-noise substrate, reducing an impact on the superconducting qubit loop conductor segment. FIGs 6A, 6B, 6C, 6D, 6E, 6F, 6G, 6H, 6I, and 6J are cross-sectional views in the X—Z plane of a superconducting circuit at successive stages of fabrication. A last shown fabrication stage of the superconducting circuit (i.e., superconducting circuit 600j shown in FIG.6J) includes a superconducting loop of a superconducting qubit with vertically differential qubit loop conductor segments. The completed circuit of superconducting circuit 600j can include a qubit body, such as qubit body 402 of qubit 400 in FIG.4, and FIG.6J can be a cross-sectional view of the X—Z plane of a portion of qubit body 402. In some implementations, the completed circuit of superconducting circuit 600j can include superconducting loops 226, 227 of qubits 201, 202 of FIG.2 and / or superconducting loop 302 of superconducting qubit 300 of FIG.3. FIG.6A illustrates a superconducting circuit 600a at a first stage of fabrication. Superconducting circuit includes a substrate 602 and a kinetic inductance layer 604 overlying substrate 602. In some implementations, kinetic inductance layer 604 directly overlies substrate 602. In alternative implementations, other layers may interpose substrate 602 and kinetic inductance layer 604. In some implementations, substrate 602 comprises one of: sapphire, quartz, silicon, silicon dioxide, silicon trioxide, and silicon nitride. It is to be understood that substrate 602 is not required to be a wafer comprised of a single material. In some implementations, substrate 602 can comprise a wafer and a low-noise electrically insulating material disposed or grown on the surface of the wafer. Kinetic inductance layer 604 can be formed of a material having a high kinetic inductance value and a high inductance value relative to other materials of complete superconducting circuit 600j, which, in some implementations, can comprise one of: titanium nitride, niobium nitride, niobium titanium nitride, aluminum nitride, and granular aluminum. The material having the high kinetic inductance value can also exhibit superconducting behavior at and below a critical temperature. Kinetic inductance layer 604 can be deposited to overlie some or all of a surface of substrate 602. In some implementations, kinetic inductance layer 604 can form kinetic inductor 302a of superconducting qubit 300 (FIG.3). FIG.6B illustrates a superconducting circuit 600b at a stage of fabrication that follows the fabrication stage shown in FIG.6A in which kinetic inductance layer 604 has been patterned to only overlie a portion of substrate 602. A portion of patterned kinetic inductance layer 604 forms or comprises a first qubit loop conductor segment 604a of the superconducting loop of a qubit in superconducting circuit 600j. Other portions of patterned kinetic inductance layer 604 are kinetic inductance layer return path termini 604b that are located on either side of first qubit loop conductor segment 604a along the cross-section of superconducting circuit 600b. FIG.6C illustrates a superconducting circuit 600c at a stage of fabrication that follows the fabrication stage shown in FIG.6B. Superconducting circuit 600c further includes a first dielectric layer 606 that overlies at least a portion of substrate 602. In some implementations, first dielectric layer 606 can be comprised of silicon dioxide or silicon nitride. FIG.6D illustrates a superconducting circuit 600d at a stage of fabrication that follows the fabrication stage shown in FIG.6C, and also includes a first superconductive wiring layer 608 that overlies at least a portion of first dielectric layer 606 and at least a portion of kinetic inductance layer 604. A mask or photoresist can be applied to first qubit loop conductor segment 604a of kinetic inductance layer 604 such that the material of first superconductive wiring layer 608 is not deposited directly thereon. First superconductive wiring layer 608 can be comprised of a material that exhibits superconducting behavior at and below a critical temperature, such as: aluminum, niobium, tantalum, and any other metal having suitable superconducting characteristics and a relatively low inductance value. FIG.6E illustrates a superconducting circuit 600e at a stage of fabrication that follows the fabrication stage shown in FIG.6D, in which first superconductive wiring layer 608 has been patterned. First layer return path portions 608a (two shown, only one called out) directly overlie kinetic inductance layer return path termini 604b (two shown, only one called out). An intermediate dielectric layer 607 can be deposited to occupy a same layer as first layer return path portions 608a, to overlie first dielectric layer 606, and to directly overlie first qubit loop conductor segment 604a. Additional relatively low inductance superconductive material can be deposited to overlie intermediate dielectric layer 607 as part of first superconductive wiring layer 608. This additional material can include: first layer return path portions 608b that directly overlie first layer return path portions 608a, and first layer shield structure portions 608c. Each first layer shield structure portion 608c is located laterally along the cross-section of superconducting circuit 600e from its respective first layer return path portions (608a, 608b), and directly overlies intermediate dielectric layer 607. FIG.6F illustrates a superconducting circuit 600f at a stage of fabrication that follows the fabrication stage shown in FIG.6E, further including a second dielectric layer 610, which overlies intermediate dielectric layer 607 and is level with a top surface of first layer return path portions 608b and first layer shield structure portions 608c. Second dielectric layer 610 can be a same or different dielectric material than the material of first dielectric layer 606 and / or intermediate dielectric layer 607, and can comprise silicon dioxide (SiO2) or silicon nitride (SiN). FIG.6G illustrates a superconducting circuit 600g at a stage of fabrication that follows the fabrication stage shown in FIG.6F, further including a second superconductive wiring layer 612 that directly overlies a portion of second dielectric layer 610 and a portion of first superconductive wiring layer 608. Second superconductive wiring layer 612 can comprise a same or different relatively low inductance superconductive material as first superconductive wiring layer 608, and may comprise one of: aluminum, niobium, and tantalum. FIG.6H illustrates a superconducting circuit 600h at a stage of fabrication that follows the fabrication stage shown in FIG.6G, in which second superconductive wiring layer 612 has been patterned to include a second qubit loop conductor segment 612a and second layer shield structure portions 612b. Second qubit loop conductor segment 612a is a second conductor of a superconducting loop of a superconducting qubit, and is located on a different layer and comprises a different material than first qubit loop conductor segment 604a. Second qubit loop conductor segment 612a directly overlies first layer return path portions 608b, forming a superconducting return path by which second qubit loop conductor segment 612a is electrically coupled to kinetic inductance layer return path termini 604b of kinetic inductance layer 604. A structure comprising second qubit loop conductor segment 612a, first layer return path portions 608a and 608b, and kinetic inductance layer return path termini 604b partially surround, or “wrap around”, first qubit loop conductor segment 604a of the superconducting loop. Hereinafter, a structure that can “partially surround” or be “partially surrounding” of one or more superconducting device or one or more superconducting metal layer can refer to a structure that indirectly or directly covers a portion of the superconducting device and / or metal layer, such that the structure extends along at least two surfaces of the superconducting device and / or metal layer. Second layer shield structure portions 612b directly overlie and superconductively electrically couple to first layer shield structure portions 608c. FIG.6I illustrates a superconducting circuit 600i at a stage of fabrication that follows the fabrication stage shown in FIG.6H, further including a third dielectric layer 614. Third dielectric layer 614 overlies second dielectric layer 610 and is level with a top surface of second layer shield structure portions 612b. Third dielectric layer 614 can be a same or different dielectric material than the material of first dielectric layer 606 and / or second dielectric layer 610, and can comprise silicon dioxide or silicon nitride. FIG.6J illustrates a superconducting circuit 600j at a stage of fabrication that follows the fabrication stage shown in FIG.6I, further including a third superconductive wiring layer 616 that directly overlies third dielectric layer 614 and at least a portion of second superconductive wiring layer 612. Third superconductive wiring layer 616 can comprise a same or different relatively low inductance superconductive material as first superconductive wiring layer 608 and / or second superconductive wiring layer 612, and may comprise one of: aluminum, niobium, and tantalum. Superconducting circuit 600j includes a shield structure 620 (delineated by bold lines), which includes a shield layer 620a on an external surface of superconducting circuit 600j (i.e., an external surface of the qubit body, such as an external surface of qubit body 402), and two shield arms 620b that protrude therethrough from shield layer 620a to first superconductive wiring layer 608 on either side of the return path along the cross-section of superconducting circuit 600j. In superconducting circuit 600j, third superconductive wiring layer 616 is shield layer 620a of shield structure 620. Each of shield arms 620b includes: one of second layer shield structure portions 612b and one of first layer shield structure portions 608c. To shield the superconducting qubit loop in superconducting circuit 600j,third superconductive wiring layer 616 overlies and superconductively electrically couples to second layer shield structure portions 612b and first layer shield structure portions 608c. Shield structure 620 of superconducting circuit 600j may further reduce crosstalk affecting the superconducting qubit loop relative to crosstalk effecting the superconducting qubit loop in superconducting circuit 500g, which includes only a planar shield structure provided by second superconductive wiring layer 512 as an external surface of superconducting circuit 500g. The multi-layer arrangement of shield structure 620 of superconducting circuit 600j surrounds at least a portion of the superconducting loop comprising first and second superconductive wiring layers 608, 612, such that it more effectively limits second qubit loop conductor segment 612a from exposure to undesired electrical and / or magnetic fields. Superconducting circuit 600j realizes the advantageous characteristics of the vertically differential qubit loop conductor segments having asymmetric inductances of superconducting circuit 500g (FIG.5G), including reductions in crosstalk that result from a large portion of the superconducting qubit loop being formed of a material having a relatively high inductance value and support for galvanic coupling to one or more couplers. Superconducting circuit 600j may further improve coherence of a superconducting qubit due to the inclusion of the return path from second qubit loop conductor segment 612a to kinetic inductance layer 604 where first qubit loop conductor segment 604a is located. The return path that partially surrounds first qubit loop conductor segment 604a, including first layer return path portions 608a and 608b, may beneficially reduce susceptibility of the superconducting qubit loop to crosstalk and increase density of electric field energy in substrate 602. In addition to the return path, partial surrounding of first qubit loop conductor segment 604a and the second qubit loop conductor segment 612a by shield structure 620 (including 608c, 612b, and 616) of superconducting circuit 600j may limit exposure to undesired electrical and / or magnetic fields. The return path and shield arms 620b are described as being formed of overlying layers of relatively low inductance superconductive material, which in some implementations, can be superconducting stud vias comprising the relatively low inductance superconductive material. In an alternative implementation, the return path and shield arms can be superconducting vias formed by drilling holes between layers and coating the holes with the relatively low inductance superconductive material. For instance, first layer return path portions 608a, 608b can be superconducting vias that galvanically couple second qubit loop conductor segment 612a and kinetic inductance layer return path termini 604b. Shield arms 620b, including first layer shield structure portion 608c and second layer shield structure portions 612b, can also be implemented as superconducting vias that extend into superconducting circuit 600j from third superconductive wiring layer 616. As previously noted, crosstalk affecting a superconducting qubit loop can be significantly reduced by arranging major axes of superconducting lines of other structures and / or devices within the quantum processor to be perpendicular to major axes of a pair of vertically differential qubit loop conductor segment of the superconducting qubit loop. However, the significant reduction of crosstalk may be contingent on maintaining symmetry about a vertical center line along a width of the entire qubit body. For example, qubit body 402 of qubit 400 (FIG.4) can have vertically differential qubit loop conductor segments of superconducting circuit 500g or superconducting circuit 600j. In order to limit the crosstalk between first and second qubit loop conductor segments (504a, 508a or 604a, 612a) and additional superconducting lines (coupled to bias connection interfaces 408a, 408b, 408c, 408d, 408e), the additional superconducting lines can be arranged perpendicularly to the major axes of vertically differential qubit loop conductor segments, and each bias connection interface (408a, 408b, 408c, 408d, 408e) can be symmetrical about the z-axis at a center location along the x-axis of qubit body 402. To meet the above-described criteria for mitigating crosstalk between vertically differential qubit loop conductor segments and superconducting lines within the quantum processor, each bias connection interface (408a, 408b, 408c, 408d, 408e) can include a pair of bias loop conductor segments that are configured to be vertically differential. FIG.7A is a cross-sectional view in the X—Z plane of a superconducting circuit 700a that includes vertically differential qubit loop conductor segments and vertically differential flux bias loop conductor segments that provide a bias connection interface. In some implementations, superconducting circuit 700a may be a partial cross-sectional view in the X—Z plane of qubit body 402 of FIG.4 that includes one of bias connection interfaces 408a, 408b, 408c, 408d, 408e. Superconducting circuit 700a includes several elements that are comparable or similar to elements of superconducting circuit 500g. More particularly: a substrate 702 of superconducting circuit 700a may be comparable or similar to substrate 502; a kinetic inductance layer 704 that includes a first qubit loop conductor segment 704a may be comparable or similar to kinetic inductance layer 504; a first dielectric layer 706 may be comparable or similar to first dielectric layer 506; a qubit loop superconductive wiring layer 712 that includes a second qubit loop conductor segment 712a may be comparable or similar to first superconductive wiring layer 508; a third dielectric layer 714 may be comparable or similar to second dielectric layer 510; and, an external superconductive wiring layer 720 may be comparable or similar to second superconductive wiring layer 512 to shield the superconducting qubit loop. As well, superconducting circuit 700a includes additional layers that form the structure of the bias connection interface. First dielectric layer 706 and qubit loop superconductive wiring layer 712 are interposed by a first intermediate wiring layer 708 and a second dielectric layer 710 that overlies first intermediate wiring layer 708. Third dielectric layer 714 and external superconductive wiring layer 720 are interposed by a second intermediate wiring layer 716 and a fourth dielectric layer 718 that overlies second intermediate wiring layer 716. At least a portion of first intermediate wiring layer 708 and at least a portion of second intermediate wiring layer 716 form or comprise respective first bias loop conductor segment 708a and a second bias loop conductor segment 716a. First bias loop conductor segment 708a on first intermediate wiring layer 708 interposes first qubit loop conductor segment 704a in kinetic inductance layer 704 and second qubit loop conductor segment 712a in qubit loop superconductive wiring layer 712. Second bias loop conductor segment 716a on second intermediate wiring layer 716 overlies second qubit loop conductor segment 712a. Both first and the second bias loop conductor segments 708a, 716a are aligned with first and the second qubit loop conductor segments 704a, 712a along the x-axis of the cross-section of superconducting circuit 700a. As such, first and second bias loop conductor segments 708a, 716a have a vertically differential configuration and advantageously have symmetry about the z-axis at a center location along the x-axis of the cross-section (labelled in FIG.7A as line Zsym). This limits cross talk between the superconducting qubit loop and the analog lines that communicatively couple to the bias loop conductor segments (708a, 716a). FIG.7B is a cross-sectional view in the X—Z plane of an alternative superconducting circuit 700b that includes vertically differential qubit loop conductor segments and vertically differential flux bias loop conductor segments that provide a bias connection interface. In some implementations, superconducting circuit 700b may be a partial cross-sectional view in the X—Z plane of qubit body 402 of FIG.4 that includes one of bias connection interfaces 408a, 408b, 408c, 408d, 408e. In some implementations, superconducting circuit 700b may include vertically differential qubit loop conductor segments (724a, 732a), a return path, and a shield structure 750 that are comparable or similar to that of superconducting circuit 600j, as well as a bias connection interface provided by a first bias loop conductor segment 728a and a second bias loop conductor segment 736a. In particular: a substrate 722 of superconducting circuit 700b may be comparable or similar to substrate 602; a kinetic inductance layer 724 that includes a first qubit loop conductor segment may be comparable or similar to kinetic inductance layer 604; a first dielectric layer 726 may be comparable or similar to first dielectric layer 606; a first intermediate wiring layer 728 may be comparable or similar to first superconductive wiring layer 608; a second dielectric layer 730 may be comparable or similar to intermediate dielectric layer 607 and second dielectric layer 610; a qubit loop superconductive wiring layer 732 may be comparable or similar to second superconductive wiring layer 612; a third dielectric layer 734 may be comparable or similar to third dielectric layer 614; and, an external superconductive wiring layer 740 may be comparable or similar to third superconductive wiring layer 616. In addition to the elements of superconducting circuit 600j, first intermediate wiring layer 728 of superconducting circuit 700b has first bias loop conductor segment 728a. Superconducting circuit 700b also includes a second intermediate wiring layer 736 and a fourth dielectric layer 738 overlying second intermediate wiring layer 736, which both interpose third dielectric layer 734 and external superconductive wiring layer 740. Second intermediate wiring layer 736 includes: second bias loop conductor segment 736a and second intermediate layer shield structure portions 736b (only one labelled in FIG.7B for clarity). Second intermediate layer shield structure portions 736b form part of shield arms 750b of shield structure 750 (delineated by bold lines), and communicatively couple a shield plane 750a of external superconductive wiring layer 740 to portions of shield structure 750 on qubit loop superconductive wiring layer 732 and first intermediate wiring layer 728. In superconducting circuit 700b, first bias loop conductor segment 728a is arranged between first and a second qubit loop conductor segments 724a, 732a along the z-axis, and second bias loop conductor segment 736a overlies second qubit loop conductor segment 732a. Both first and the second bias loop conductor segments 728a, 736a are aligned with first qubit loop conductor segment 724a along the x-axis of the cross-section of superconducting circuit 700b, thereby fulfilling criteria of symmetry along line Zsymto reduce crosstalk as described with respect to superconducting circuit 700a of FIG.7A. In alternative implementations, portions of shield structure 750 and the return path of FIG.7B can be implemented as superconducting vias, as described previously with respect to FIG.6J. FIG.8A is a plan view of a portion of a superconducting circuit 800. Portion of superconducting circuit 800 can be one of superconducting circuit 700a or 700b (FIGs 7A and 7B). FIG.8A can illustrate a top plan view of superconducting circuit 700a or 700b in the X—Y plane, which excludes visual representations of dielectric layers (such as: dielectric layers 706, 710, 714, and 718 of superconducting circuit 700a or dielectric layers 726, 730, 734 and 738 of superconducting circuit 700b). FIG 8A can be a region of qubit 400 in FIG.4 that includes one of bias connection interfaces 408a, 408b, 408c, 408d, 408e. FIG.8A includes: a substrate 802; a kinetic inductance layer 804 overlying substate 802; a qubit loop wiring layer 812 overlying kinetic inductance layer 804; a second intermediate wiring layer 816 overlying qubit loop wiring layer 812; and, an external wiring layer 820 overlying qubit loop wiring layer 812. In FIG.8A, a pair of analog lines that includes a first and a second analog line 830a, 830b are respectively coupled to a first and a second bias line interface 820a, 820b of external wiring layer 820. FIG.8B is a cross-sectional view of portion of superconducting circuit 800 in the Y—Z plane. The cross-sectional view illustrates a flux bias loop 840 (delineated by bolded lines) that spans across multiple superconducting layers of the portion of the superconducting circuit 800. Flux bias loop 840 is not shown as a closed loop in FIG.8B, and terminates at first and second bias line interfaces 820a, 820b that respectively communicatively couple to first and second analog lines 830a, 830b (FIG.8A). In some implementations, flux bias loop 840 can perform the functions of interface 222 or 223 of circuit 200 to couple bias signals into superconducting loop 226 or 227 of first or second qubit 201 or 202 (see FIG. 2). In the cross-sectional view of superconducting circuit 800 in FIG.8B, flux bias loop 840 surrounds, and is communicatively coupled to, only a small portion of the length of the superconducting qubit loop. As illustrated in the cross-sectional view of FIG.8B, portion of superconducting circuit 800 includes a first intermediate wiring layer 808 that is visually obstructed in the plan view of FIG.8A. First intermediate wiring layer 808 indirectly overlies kinetic inductance layer 804 and includes a first bias loop conductor segment 808a, which can be a bias loop conductor segment of first intermediate wiring layer 708 of FIG.7A or first bias loop conductor segment 728a of FIG.7B. First bias loop conductor segment 808a interposes a first qubit loop conductor segment 804a of kinetic inductance layer 804 and a second qubit loop conductor segment 812a of qubit loop wiring layer 812. The cross-sectional view of portion of superconducting circuit 800 also illustrates dielectric layers thereof that are not illustrated in FIG.8A. More particularly: a first dielectric layer 806 directly overlies kinetic inductance layer 804, and can be first dielectric layer 706 of FIG.7A or first dielectric layer 726 of FIG.7B; a second dielectric layer 810 directly overlies first intermediate wiring layer 808, and can be second dielectric layer 710 of FIG.7A or second dielectric layer 730 of FIG.7B; a third dielectric layer 814 directly overlies qubit loop wiring layer 812, and can be third dielectric layer 714 of FIG.7A or third dielectric layer 734 of FIG.7B; and, a fourth dielectric layer 818 directly overlies second intermediate wiring layer 816, and can be fourth dielectric layer 718 of FIG.7A or fourth dielectric layer 738 of FIG.7B. Flux bias loop 840 also includes a second bias loop conductor segment 816a (two shown, only one called out for visual clarity), which is part of second intermediate wiring layer 816. In cross-sectional view of portion of superconductive circuit 800 of FIG.8B, it can be seen that bias loop portions 808b of first intermediate wiring layer 808 and bias loop portions 812b of qubit loop wiring layer 812 communicatively couple first bias loop conductor segment 808a and second bias loop conductor segment 816a, such that flux bias loop 840 substantially surrounds a portion of second qubit loop conductor segment 812a. Flux bias loop 840 also includes bias loop portions 816b (two shown, only one called out for visual clarity) of second intermediate wiring layer 816, which respectively directly underlie first and second bias line interfaces 820a, 820b. As such, signals for biasing the superconducting qubit loop are transmitted by first and second analog lines 830a, 830b of FIG.8A through first and second bias line interfaces 820a, 820b to flux bias loop 840, and are coupled to the superconducting qubit loop via second qubit loop conductor segment 812a. In alternative implementations, bias loop portions 808b, 812b can be superconducting vias extending between first bias loop conductor segment 808a and second bias loop conductor segment 816a. First and second bias line interfaces 820a, 820b can also be electrically coupled to second bias loop conductor segment 816a by superconducting vias. Due to a magnetic field strength generated by a first qubit loop conductor segment on a kinetic inductance layer, such as kinetic inductance layer 504 or 604, being disproportionately small relative to the impedance per unit length, magnetic coupling of a qubit to a coupler may be unsuitable. Instead, the qubit and coupler can be galvanically coupled with a high coupling strength to ensure proper communication therebetween. Although uncontrolled galvanic coupling between a plurality of superconducting loops may be disadvantageous to qubit operation, careful design of the superconducting qubit loop and placement of coupler connection interface leads can limit the undesired effects. Herein, a “lead” or “segment” can refer to a conductive line, wire, or trace, or a portion of a conductive line, wire, or trace, that can electrically couple two or more devices, structures, or conductors. FIGs 9A, 9B, and 9D are plan views of a portion of a superconducting circuit 900a, 900b, 900d at various fabrication stages. FIGs 9A, 9B, and 9D illustrate a cross-sectional view of a portion of a superconducting qubit body in the X—Y plane, and omit visual representations of dielectric layers (such as: first and second dielectric layers 506, 510 of superconducting circuit 500g or first, second, and third dielectric layers 606, 610, 614 of superconducting circuit 600j). Though, a person skilled in the art would understand that portions of superconducting circuit 900a, 900b, 900d include dielectric layers arranged between the illustrated layers in a manner as previously described. FIGs 9A, 9B, and 9D can be a region of qubit 400 in FIG.4 that includes one of coupler connection interfaces 406a, 406b, 406c, 406d. Portion of superconducting circuit 900a of FIG.9A illustrates a plan view of the circuit at a first intermediate stage of fabrication taken along a cutting plane A—A of FIG.9C or FIG.9E. Portion of superconducting circuit 900a includes a substrate 902 and a kinetic inductance layer 904. In some implementations, substrate 902 may be one of substrate 502, 602, and 702. In some implementations, kinetic inductance layer 904 may be one of kinetic inductance layer 504, 604, and 704, and the illustrated portion of kinetic inductance layer 904 in FIG.9A may be a portion of a first qubit loop conductor segment of a superconducting qubit loop. A major axis of the superconducting qubit loop is labelled in FIG.9A as dashed line Q—Q. Kinetic inductance layer 904 directly overlies substrate 902. Kinetic inductance layer 904 includes a first coupler connection lead 904a and a second coupler connection lead 904b that are arranged in a horizontally differential configuration (spaced within a same plane or layer in a fabrication stack). Portion of superconducting circuit 900b of FIG.9B illustrates a plan view of portion of superconducting circuit 900a at a later stage of fabrication taken along a cutting plane B—B of FIG.9C, according to one implementation in which the pair of coupler connections interfaces are vertically differential. FIG.9B includes all of the elements of FIG.9A, and additionally includes a qubit loop wiring layer 912. In some implementations, qubit loop wiring layer 912 can be: second superconductive wiring layer 612 of FIG.6J, qubit loop superconductive wiring layer 712 of FIG.7A, or qubit loop superconductive wiring layer 732 of FIG.7B. The illustrated portion of qubit loop wiring layer 912 in FIG.9B may be a portion of a second qubit loop conductor segment of the superconducting qubit loop. In FIG.9B, first and second coupler connection interfaces 930a, 930b (shown in bolded lines in FIGs 9B and 9C) extend through portion of superconducting circuit 900b to galvanically couple first and second coupler connection leads 904a, 904b to respective first and second coupler leads 940a, 940b. As can be seen in FIG.9B, first and second coupler leads 940a, 940b extend in a direction that is perpendicular to the major axes (labelled in FIG.9B as dashed line Q—Q) of the first qubit loop conductor segment in kinetic inductance layer 904 and the second qubit loop conductor segment in qubit loop wiring layer 912. Resultantly, symmetry of the qubit body about a line along z- axis at the center of the x-axis is maintained, and undesired crosstalk is limited from a coupler connected to first and second coupler leads 940a, 940b. FIG.9C is a cross-sectional view of a superconducting circuit 900c in the Y—Z plane that includes a pair of vertically differential coupler connection interfaces of a qubit. In some implementations, portion of the superconducting circuit 900c is a portion of qubit 400 that includes one of coupler connection interfaces 406a, 406b, 406c, 406d. Superconducting circuit 900c can be a view of portion of superconducting circuit 900b in the Y—Z plane that also includes dielectric layers and layers that overlie qubit loop wiring layer 912. Superconducting circuit 900c includes: substate 902; kinetic inductance layer 904; a first dielectric layer 906 overlying the kinetic inductance layer 904; a first intermediate wiring layer 908 overlying at least kinetic inductance layer 904; a second dielectric layer 910 overlying at least first dielectric layer 906; qubit loop wiring layer 912 overlying at least second dielectric layer 910; a third dielectric layer 914 overlying at least qubit loop wiring layer 912; a second intermediate wiring layer 916 overlying at least third dielectric layer 914; a fourth dielectric layer 918 overlying at least second intermediate wiring layer 916; a third intermediate wiring layer 920 overlying at least fourth dielectric layer 918; a fifth dielectric layer 922 overlying at least third intermediate wiring layer 920; and, a shield wiring layer 924 overlying at least fifth dielectric layer 922. All of first intermediate wiring layer 908, qubit loop wiring layer 912, second intermediate wiring layer 916, third intermediate wiring layer 920, and shield wiring layer 924 can comprise at least one material having relatively low inductance and kinetic inductance values, which exhibits superconducting behavior at and below a respective critical temperature. Kinetic inductance layer 904 can comprise a material having a relatively high kinetic inductance value that exhibits superconducting behavior at and below a critical temperature. In FIG.9C, it can be seen that first and second coupler connection interfaces 930a, 930b (delineated using bolded lines) that couple to first and second coupler connection leads 940a, 940b shown in FIG.9B extend through superconducting circuit 900c to first and second coupler connection leads 904a, 904b of kinetic inductance layer 904. First and second coupler connection interfaces 930a, 930b include: first layer coupler connection portions 908a, 908b of first intermediate wiring layer 908; qubit loop wiring layer coupler connection portions 912a, 912b of qubit loop wiring layer 912; and, second layer coupler connection portions 916a, 916b of second intermediate wiring layer 916. Referring again to FIG.9B, first coupler lead 940a directly galvanically couples to second layer coupler connection portion 916a of first coupler connection interface 930a to communicatively couple first coupler lead 940a to first coupler connection lead 904a. Second coupler connection interface 930b also includes third layer coupler connection portion 920b of third intermediate wiring layer 920. Second coupler lead 940b directly galvanically couples to third layer coupler connection portion 920b of second coupler connection interface 930b to communicatively couple second coupler lead 940b to second coupler connection lead 904b. With reference to FIG.9C, second layer coupler connection portion 916a can also be referred to as a “first coupler connection site” and third layer coupler connection portion 920b can also be referred to as a “second coupler connection site” within the qubit body. First and second coupler connection interfaces 930a, 930b extend between first and second coupler connection leads 904a, 904b to first and second coupler connection sites (916a, 920b), respectively. At first coupler connection site (916a), which is located on second intermediate wiring layer 916, first coupler connection interfaces 930a directly galvanically couples to first coupler lead 940a. At second coupler connection site (920b), which is located on third intermediate wiring layer 920 and overlies first coupler connection site (916a), second coupler connection interfaces 930b directly galvanically couples to second coupler lead 940b. Dashed line A—A in FIG.9C is marked at an external surface of kinetic inductance layer 904, and indicates a cutting plane of the z-axis of superconducting circuit 900c that corresponds to the top layer of the plan view of portion of superconducting circuit 900a. Dashed line B—B in FIG.9C indicates a cutting plane of the z-axis of superconducting circuit 900c that corresponds to the portion of superconducting circuit 900c seen in the plan view of FIG.9B (i.e., portion of superconducting circuit 900b). Portion of a superconducting circuit 900d of FIG.9D illustrates a plan view of portion of superconducting circuit 900a at a later stage of fabrication taken along a cutting plane D—D of FIG.9E, according to an implementation in which the pair of coupler connections interfaces are horizontally differential. FIG.9D includes all of the elements of FIG.9A and qubit loop wiring layer 912. FIG.9D also includes first and second coupler connection interfaces 930c, 930d that extend through superconducting circuit 900d to galvanically couple first and second coupler connection leads 904a, 904b to respective first and second coupler leads 940c, 940d. Unlike first and second coupler connection interfaces 930a, 930b of FIG.9B, first and second coupler connection interfaces 930c, 930d are arranged on a same layer of the fabrication stack such that one does not overlie the other. Although it is shown in FIGs 9B and 9D that major axes of first and second coupler leads (940a, 940b and 940c, 940d) are perpendicular to the major axes of the first qubit loop conductor segment on kinetic inductance layer 904 and the second qubit loop conductor segment on qubit loop wiring layer 912 (labelled in FIG.9D as dashed line Q—Q), these are only examples and not intended to be limiting. In alternative implementations, coupler leads can meet major axes of the qubit loop conductor segments at other angles (e.g., other angles that such that major axes of coupler leads are neither perpendicular nor parallel with major axes of qubit loop conductor segments). FIG.9E is a cross-sectional view of a superconducting circuit 900e in the Y—Z plane that includes a pair of horizontally differential coupler connection interfaces. Superconducting circuit 900e can be a view of portion of superconducting circuit 900d of FIG.9D in the Y—Z plane that also includes dielectric layers and layers that overlie qubit loop wiring layer 912. In FIG.9E, it can be seen that first and second coupler connection interfaces 930c, 930d (delineated using bolded lines) that couple to first and second coupler leads 940c, 940d as shown in FIG.9D, extend through superconducting circuit 900e to first and second coupler connection leads 904a, 904b of kinetic inductance layer 904. First and second coupler connection interfaces 930c, 930d include: first layer coupler connection portions 908a, 908b; qubit loop wiring layer coupler connection portions 912a, 912b; and second layer coupler connection portions 916c, 916d. First and second coupler leads 940c, 940d directly galvanically couple to second layer coupler connection portions 916c, 916d of first coupler connection interface 930c, 930d. As galvanic coupling of first and second coupler leads 940c, 940d to first and second coupler connection leads 904a, 904b occurs at second intermediate wiring layer 916, third intermediate wiring layer 920 and fifth dielectric layer 922 of FIG.9C are not included in superconducting circuit 900e, and a shield wiring layer 924b overlies fourth dielectric layer 918. With reference to FIG.9E, second layer coupler connection portion 916c can also be referred to as a “first coupler connection site” and second layer coupler connection portion 916d can also be referred to as a “second coupler connection site” within the qubit body. First and second coupler connection interfaces 930c, 930d extend between first and second coupler connection leads 904a, 904b to first and second coupler connection sites (916c, 916d), respectively. First and second coupler leads 940c, 940d directly galvanically couple to first and second coupler connection interfaces 930c, 930d, respectively, at first and second coupler connection sites (916c, 916d). Both the first and second coupler connection sites (916c, 916d) are located on second intermediate wiring layer 916 that overlies qubit loop wiring layer 912. Line A—A in FIG.9E is marked at an external surface of kinetic inductance layer 904, and indicates a cutting plane of the z-axis of superconducting circuit 900e that corresponds to the top layer of the plan view of portion of superconducting circuit 900a. Dashed line D—D in FIG.9E indicates a cutting plane of the z-axis of superconducting circuit 900e that corresponds to the portion of superconducting circuit 900e seen in the plan view in FIG.9D (i.e., portion of superconducting circuit 900d). Returning to FIG.4, it can be seen that coupler connection interfaces 406a, 406b, 406c, 406d are located distally from Josephson junction 404 along qubit body 402. Due to the large inductance per unit length of the kinetic inductance material of the first qubit loop conductor segment, this leads to a significant proportion of the total qubit inductance being between Josephson junction 404 and coupler connection interfaces 406a, 406b, 406c, 406d. In FIGs 9A, 9B, and 9D, the high inductance path can be realized along kinetic inductance layer 904 and through coupler connection leads 904a, 904b. The high inductance path can have an impedance that beneficially provides sufficient electrical separation between Josephson junction 404 and coupler connection interfaces 406a, 406b, 406c, 406d to prevent adverse effects. A low inductance return path that completes the superconductive qubit loop of qubit body 402 can be realized along qubit loop wiring layer 912. For example, for qubit 400, the relatively low inductance return path can extend on a superconductive wiring layer, such as qubit loop wiring layer 912, between coupler connection interface 406a and coupler connection interface 406d. Asymmetry of the qubit loop conductor segment inductance allows for more granular control of the proportion of total qubit inductance that is arranged between qubit structures. Methods FIG.10 is a flowchart illustrating a method 1000 to fabricate a superconducting circuit that includes a superconducting qubit loop with vertically differential qubit loop conductor segments, in accordance with the present articles and methods. Method 1000 provides an example method to fabricate any one of superconducting circuits 500g, 600j, 700a, 700b, 800, 900b, 900c, 900d, 900e, and any other superconducting circuit described above. In some implementations, the superconducting circuit fabricated by method 1000 can include at least a portion of a superconducting qubit, such as qubit 400 of FIG.4 in which qubit body 402 includes a superconducting qubit loop that has a pair of vertically differential qubit loop conductor segments. In some implementations, the superconducting circuit fabricated by method 1000 can include at least a portion of superconducting qubit 300 of FIG.3 or one of first and second qubits 201, 202 of FIG.2. In some implementations, the superconducting circuit fabricated by method 1000 can include at least a portion of a superconducting qubit within quantum processor 126 in computing system 100 of FIG.1. Method 1000 includes acts 1002 to 1022, though in other implementations, certain acts may be omitted and / or additional acts may be added. Method 1000 may be performed by, for example, integrated circuit fabrication equipment in response to an initiation of a fabrication process. At 1002, a kinetic inductance layer is formed on, or in other words to directly overlie, a substrate. The kinetic inductance layer comprises a material having a high kinetic inductance and a relatively high inductance value. The formation of the kinetic inductance layer includes formation of a first device loop conductor segment of a superconducting loop of a body of a superconducting controllable device. In some implementations, the material having a relatively high inductance value is one of: niobium nitride, niobium titanium nitride, titanium nitride, aluminum nitride, and granular aluminum. In some implementations, the substrate can comprise a low-noise electrically insulating material. Formation of the kinetic inductance layer can include formation of a layer that includes at least a first qubit loop conductor segment of a superconducting qubit loop of a qubit body. In some implementations, kinetic inductance layer may only include the first qubit loop conductor segment, such as in superconducting circuits 500g and 700a. In other implementations, formation of kinetic inductance layer may also include formation of a portion of a return path of a second qubit loop conductor segment. For instance, superconducting circuit 600j includes kinetic inductance layer return path termini 604b (FIGs 6B, 6J). In other implementations, formation of the kinetic inductance layer can include formation of a layer that includes at least a first device loop conductor segment of a superconducting coupler loop of a coupler body of a superconducting coupler. In other implementations, formation of the kinetic inductance layer can include formation of a layer that includes at least a first device loop conductor segment of a superconducting body loop of a quantum flux parametron (QFP). In some implementations, formation of the kinetic inductance layer includes deposition of the superconductive material having the high kinetic inductance and relatively high inductance value onto the low-noise electrically insulating material of the substrate. For example, this may be depositing kinetic inductance layer 504 on substrate 502 as shown in FIG.5A or depositing kinetic inductance layer 604 on substrate 602 as shown in FIG.6A. The deposition of the superconductive material having the relatively high inductance value can be performed using a variety of deposition techniques. Formation of the kinetic inductance layer may also include patterning the superconductive material having the relatively high inductance value after deposition. For example, the superconducting circuit following patterning of the kinetic inductance layer may be superconducting circuit 500b of FIG.5B or superconducting circuit 600b of FIG.6B. Patterning the kinetic inductance layer may include masking, etching, and / or planarizing at least a portion of the kinetic inductance layer. In some implementations, masking may include application of a photoresist to a portion of the high kinetic inductance layer, and etching may include use of chemical and / or physical etching techniques. As used herein, “deposition and patterning” may include both an initial formation operation where a uniform layer of material is deposited onto an underlying surface and subsequent patterning operations (e.g., planarizing, masking, etching) performed on the material to form wiring, devices, and other structures. It will be understood that similar deposition techniques may be used in the other depositing acts described herein. At 1004, a first dielectric layer is formed, which overlies at least a portion of the kinetic inductance layer. In some implementations, first dielectric layer is comprised of a dielectric material, such as silicon dioxide or silicon nitride. Formation of the first dielectric layer may include deposition of the dielectric material over the kinetic inductance layer, and planarization of an external surface of the deposited dielectric material. In some implementations, formation of the first dielectric layer may include formation of the first dielectric layer to directly overlie a portion of the substrate and the kinetic inductance layer. For example, in FIG.5C, first dielectric layer 506 directly overlies substrate 502 and kinetic inductance layer 504. In such implementations, deposited material of first dielectric layer 506 may be deposited and planarized to have a fixed height (i.e., a dimension along the z-axis of the cross-section of the multi-layer fabrication stack) that exceeds a height of kinetic inductance layer 504. In other implementations, formation of the first dielectric layer may include formation of the first dielectric layer to directly overlie a portion of the substrate and a portion of the kinetic inductance layer that includes the first qubit loop conductor segment. For example, in FIG.6C, first dielectric layer 606 directly overlies a portion of substrate 602 and first qubit loop conductor segment 604a on kinetic inductance layer 604. However, first dielectric layer 606 does not overlie kinetic inductance layer return path termini 604b, such that deposited material of first dielectric layer 606 may be deposited and planarized to have a same height. At 1006, a device loop superconductive wiring layer is formed. The device loop superconductive wiring layer overlies at least a portion of the first dielectric layer. The device loop superconductive wiring layer comprises a material that has a relatively low inductance value in comparison to the material of the kinetic inductance layer, and exhibits superconducting behavior at and below a critical temperature. In some implementations, the device loop superconductive wiring layer comprises at least one of: aluminum, niobium, and tantalum. At least a portion of the device loop superconductive wiring layer is a second device loop conductor segment of the superconducting loop of the body of the superconducting controllable device. In implementations in which the first device loop conductor segment is a first qubit loop conductor segment of a superconducting qubit loop, the device loop superconductive wiring layer is a qubit loop superconductive wiring layer, and formation of at least the second device loop conductor segment includes formation of at least a second qubit loop conductor segment. In implementations in which the first device loop conductor segment is a first coupler loop conductor segment of a superconducting coupler loop, the device loop superconductive wiring layer includes formation of at least a second coupler loop conductor segment. In implementations in which the first device loop conductor segment is a first device loop conductor segment of a superconducting body loop of a QFP, the device loop superconductive wiring layer includes formation of at least a second device loop conductor segment of the QFP. In some implementations in which the device loop superconductive wiring layer is a qubit loop superconductive wiring layer, the qubit loop superconductive wiring layer directly overlies at least a portion of the first dielectric layer, such as in superconducting circuits 500g and 600j. In other implementations, the qubit loop superconductive wiring layer overlies one or more additional layers that interleave the first dielectric layer and the qubit loop superconductive wiring layer. For instance, second dielectric layers 710, 730 and first intermediate wiring layers 708, 728 of superconducting circuits 700a, 700b interpose first dielectric layers 706, 726 and qubit loop superconductive wiring layers 712, 732. Formation of the device loop superconductive wiring layer includes formation of a layer that includes at least the second device loop conductor segment. In some implementations, the loop superconductive wiring layer may only include the second device loop conductor segment, such as in first superconductive wiring layer 508 of superconducting circuits 500g and qubit loop superconductive wiring layer 712 of superconducting circuit 700a. In other implementations, formation of the device loop superconductive wiring layer may also include formation of a portion of a shield structure. For instance, superconducting circuit 600j includes second layer shield structure portions 612b (FIGs 6E, 6J) of shield structure 620. In some implementations, formation of the device loop superconductive wiring layer includes deposition of the relatively low inductance superconductive material onto at least a dielectric layer of the superconducting circuit. For example, this may be deposition of first superconductive wiring layer 508 on first dielectric layer 506 as shown in FIG.5D or deposition of first superconductive wiring layer 608 on first dielectric layer 608 as shown in FIG.6D. In some implementations, formation of the device loop superconductive wiring layer also includes patterning the deposited material using masking, etching and / or planarizing techniques. For example, the superconducting circuit following patterning of the device loop superconductive wiring layer may be superconducting circuit 500e of FIG.5E or superconducting circuit 600e of FIG. 6E. In some implementations, additional acts may be included in method 1000. Some or all of optional acts 1008, 1010, 1012, and 1014, 1016, 1018, 1020, and 1022 may be performed as part of method 1000, which are shown in broken line boxes in FIG 10. Optional acts 1008 and 1010 may be performed after act 1004 and optionally before act 1006. At 1008, a first intermediate superconductive wiring layer can be formed to directly overlie at least the first dielectric layer. Formation of the first intermediate superconductive wiring layer can include deposition and patterning of a layer of relatively low inductance material that exhibits superconductive material at and below a critical temperature. In some implementations, formation of the first intermediate superconductive wiring layer can include formation of portions of a device loop conductor segment return path and portions of the shield structure, such as first layer return path portions 608a, 608b and first layer shield structure portion 608c of first superconductive wiring layer 608 of FIG.6E and as shown in FIG.7B. First superconductive wiring layer 608 of FIG.6E and first intermediate wiring layer 728 of FIG.7B are formed to directly overlie portions of first dielectric layers 606, 726 and return path termini of kinetic inductance layers 604, 724. In some implementations, formation of the first intermediate superconductive wiring layer can additionally or alternatively include formation of a first conductor segment of a pair of bias loop conductor segments, such as the first bias loop conductor segment on first intermediate wiring layers 708, 728 of FIGs 7A and 7B. At 1010, a second dielectric layer can be formed to overlie at least the first intermediate superconductive wiring layer. Formation of the second dielectric layer can include deposition of a same or different dielectric material as the material of the first dielectric layer, and planarization of the deposited dielectric material. In some implementations, the second dielectric layer can be formed to directly overlie a portion of the first dielectric layer and a portion of the first intermediate superconductive wiring layer, such as in FIGs 6F and 7B. In implementations that include optional acts 1008 and 1010, optional acts 1012 and 1014 may be performed after act 1006. At 1012, a third dielectric layer can be formed to directly overlie at least a portion of the device loop superconductive wiring layer. In some implementations, formation of the third dielectric layer includes deposition of a same or different dielectric material as the material of the first and second dielectric layers, and planarization of the deposited dielectric material. In some implementations, the third dielectric layer can be formed to directly overlie a portion of the second dielectric layer and a portion of the device (e.g., qubit) loop superconductive wiring layer, such as in FIGs 6I and 7B. At 1014, a second intermediate superconductive wiring layer can be formed to directly overlie at least the third dielectric layer. Formation of the second intermediate superconductive wiring layer can include deposition and patterning of a relatively low inductance material that exhibits superconductive material at and below a critical temperature. The material can be a same or different material than the first intermediate superconductive wiring layer and the device loop superconductive wiring layer. Formation of the second intermediate superconductive wiring layer can include formation of a second bias loop conductor segment of the pair of bias loop conductor segments, such as the second bias loop conductor segments 716a, 736a on second intermediate wiring layers 716, 736 of FIGs 7A and 7B. In some implementations, formation of the second intermediate superconductive wiring layer can also include formation of portions of the shield structure. For instance, this can include formation of second intermediate layer shield structure portions 736b of second intermediate wiring layer 736 that are part of shield structure 750 of superconducting circuit 700b, which are formed to directly overlie portions of third dielectric layer 734 and shield structure portions of qubit loop superconductive wiring layer 732 (FIG.7B). In some implementations, method 1000 includes formation of coupler connection interfaces, such as coupler connection interfaces 406a, 406b, 406c, and 406d of FIG.4 or first and second coupler connection interfaces 930c, 930c of FIGs 9D and 9E. In such implementations: act 1002 includes formation of first and second coupler connection leads 904a, 904b as part of kinetic inductance layer 904 (FIG.9D); act 1008 includes formation of first layer coupler connection portions 908a, 908b; act 1006 includes formation of qubit loop wiring layer coupler connection portions 912a, 912b; and, act 1014 includes formation of second layer coupler connection portions 916c, 916d. Second layer coupler connection portion 916c of first coupler connection interface 930c and second layer coupler connection portion 916d of second coupler connection interface 930d can respectively communicatively couple a pair of coupler leads (940c, 940d) to first and second coupler connection leads 904a, 904b. In implementations that include optional acts 1012 and 1014, optional act 1016 may be performed after act 1014. In implementations that do not include optional acts 1012 and 1014, optional act 1016 may be performed after act 1006. At 1016, a fourth dielectric layer is formed. Formation of the fourth dielectric can include deposition of a dielectric material, which can be a same or different material than the dielectric material of first, second, and third dielectric layers, and planarization of the deposited dielectric material. In implementations that include optional acts 1012 and 1014, formation of the fourth dielectric layer can include formation of the fourth dielectric layer to overlie at least the third dielectric layer. For instance, fourth dielectric layer 718 of superconducting circuit 700a directly overlies third dielectric layer 714 (FIG.7A), and fourth dielectric layer 738 of superconducting circuit 700b directly overlies third dielectric layer 734 and second intermediate wiring layer 736. In implementations that do not include optional acts 1012 and 1014, formation of the fourth dielectric layer can include formation of the fourth dielectric layer to overlie at least the first dielectric layer and the loop superconductive wiring layer. For instance, second dielectric layer 510 in superconducting circuit 500f is formed to directly overlie first superconductive wiring layer 508 and at least a portion of first dielectric layer 506 (FIG.5F). In another example, third dielectric layer 614 in superconducting circuit 600i is formed to directly overlie second superconductive wiring layer 612 and at least a portion of second dielectric layer 610 (FIG.6I). Some implementations that include optional acts 1012, 1014, and 1016 may also include optional acts 1018 and 1020 in instances in which the method includes formation of coupler connection interfaces, such as coupler connection interfaces 406a, 406b, 406c, and 406d of FIG.4 or first and second coupler connection interfaces 930a, 930b of FIGs 9A and 9B. In such implementations: act 1002 includes formation of first and second coupler connection leads 904a, 904b as part of kinetic inductance layer 904 (FIG.9B); act 1008 includes formation of first layer coupler connection portions 908a, 908b; act 1006 includes formation of qubit loop wiring layer coupler connection portions 912a, 912b; and, act 1014 includes formation of second layer coupler connection portions 916a, 916b, of which second layer coupler connection portion 916a of first coupler connection interface 930a can communicatively couple one of a pair of coupler leads to first coupler connection lead 904a. At act 1018, a third intermediate superconductive wiring layer is formed that directly overlies at least a portion of the fourth dielectric layer. Formation of the third intermediate superconductive wiring layer can include deposition and patterning of a relatively low inductance material that exhibits superconductive material at and below a critical temperature. The material can be a same or different material than one or more of: the second intermediate superconductive wiring layer, the first intermediate superconductive wiring layer, and the device loop superconductive wiring layer. Formation of the third intermediate superconductive wiring layer can include formation of a third layer coupler connection portion 920b of second coupler connection interface 930b (FIG.9B) that galvanically couples a second one of the pair of coupler leads to second coupler connection lead 904b. In some implementations, formation of the third intermediate superconductive wiring layer includes formation of third layer shield structure portions of a shield structure that directly overlie second layer shield structure portions of the second intermediate wiring portion. At act 1020, a fifth dielectric layer is formed that directly overlies at least a portion of the third intermediate superconductive wiring layer. Formation of the fifth dielectric layer can include deposition of a dielectric material and planarization of the deposited dielectric material. The dielectric material can be a same or different material than the dielectric material of one or more of: the first, the second, the third, and the fourth dielectric layers. At 1022, a shield superconductive wiring layer is formed to directly overlie at least a portion of an immediately underlying dielectric layer. Formation of the shield superconductive wiring layer can include deposition and planarization of a layer of a material that exhibits superconducting behavior at and below a critical temperature. The material can be a same or different material than a material comprised by other superconductive wiring layers of the superconducting circuit, and can be one of: aluminum, niobium, and tantalum. Formation of the shield superconductive wiring layer provides a planar portion of a shield structure on an external layer of the superconducting circuit. In some implementations that exclude optional acts 1018 and 1020, the shield superconductive wiring layer is formed to directly overlie only the fourth dielectric layer. In other implementations, the shield structure includes a pair of shield arms to at least partially surround the second device loop conductor segment and, in some implementations, the return path (see, for example, shield structure 750 of FIG.7B includes a shield plane 750a and shield arms 750b that partially surround second qubit loop conductor segment 732a). The shield arms extend from the shield superconductive wiring layer into the multi-layer fabrication stack of the superconducting circuit, and comprise shield structure portions in all other superconductive wiring portions of the superconducting circuit. The shield superconductive wiring layer is formed to directly overlie at least a portion of the fourth dielectric layer in implementations that exclude optional acts 1018 and 1020, in which the shield superconductive wiring layer directly overlies shield structure portions of the device loop superconductive wiring layer (such as shield layer 620a comprised of third superconductive wiring layer 616 in FIG.6J) or shield structure portions of the second intermediate superconductive wiring layers (for instance, shield plane 750a comprising external superconductive wiring layer 740 directly overlying second intermediate layer shield structure portions 736b of shield arms 750b in FIG.7B). The shield superconductive wiring layer is formed to directly overlie at least a portion of the fifth dielectric layer in implementations that include optional acts 1018 and 1020, in which the shield superconductive wiring layer can directly overlie shield structure portions of the third intermediate wiring layer (such as shield wiring layer 924 in FIG.9B). Post-Amble The above described method(s), process(es), or technique(s) could be implemented by a series of processor readable instructions stored on one or more nontransitory processor-readable media. Some examples of the above described method(s), process(es), or technique(s) method are performed in part by a specialized device such as an adiabatic quantum computer or a quantum annealer or a system to program or otherwise control operation of an adiabatic quantum computer or a quantum annealer, for instance a computer that includes at least one digital processor. The above described method(s), process(es), or technique(s) may include various acts, though those of skill in the art will appreciate that in alternative examples certain acts may be omitted and / or additional acts may be added. Those of skill in the art will appreciate that the illustrated order of the acts is shown for example purposes only and may change in alternative examples. Some of the example acts or operations of the above described method(s), process(es), or technique(s) are performed iteratively. Some acts of the above described method(s), process(es), or technique(s) may be performed during each iteration, after a plurality of iterations, or at the end of all the iterations. The above description of illustrated implementations, including what is described in the Abstract, is not intended to be exhaustive or to limit the implementations to the precise forms disclosed. Although specific implementations of and examples are described herein for illustrative purposes, various equivalent modifications can be made without departing from the spirit and scope of the disclosure, as will be recognized by those skilled in the relevant art. The teachings provided herein of the various implementations can be applied to other methods of quantum computation, not necessarily the example methods for quantum computation generally described above. The various implementations described above can be combined to provide further implementations. All of the commonly assigned U.S. patent application publications, U.S. patent applications, foreign patents, and foreign patent applications referred to in this specification and / or listed in the Application Data Sheet are incorporated herein by reference, in their entirety, including but not limited to: U.S. Patents No.6,627,916; 7,533,068; 7,687,938; 7,876,248; 8,008,942; 8,035,540; 8,098,179; 8,169,231; 8,190,548; 8,195,596; 8,421,053; 8,854,074; 8,951,808; 9,424,526; 9,768,371; 10454015; 10,938,346; and, 11,424,521; U.S. Patent Application Publications No.2018 / 0219150 (granted as U.S. Patent No.10454015) and 2022 / 0207404; U.S. Provisional Patent Application No.63 / 396,340 (published as International Patent Application WO2024102504); and, International Patent Application Publication WO2022178130. These and other changes can be made to the implementations in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific implementations disclosed in the specification and the claims, but should be construed to include all possible implementations along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.

Claims

CLAIMS 1. A superconducting circuit comprising: a substrate; a kinetic inductance layer comprising a material having a relatively high inductance value and exhibiting superconducting behavior at and below a critical temperature, the kinetic inductance layer directly overlying the substrate, wherein at least a first portion of the kinetic inductance layer is a first device loop conductor segment of a superconducting loop of a body of a superconducting controllable device; a first dielectric layer overlying at least a portion of the kinetic inductance layer; and, a device loop superconductive wiring layer overlying the first dielectric layer, the device loop superconductive wiring layer comprising a relatively low inductance superconductive material having a relatively low inductance value and exhibiting superconducting behavior at and below a critical temperature, the relatively low inductance superconductive material having a low inductance value in comparison to the relatively high inductance value, wherein at least a portion of the device loop superconductive wiring layer is a second device loop conductor segment of the superconducting loop.

2. The superconducting circuit of claim 1, further comprising: a second dielectric layer overlying at least a portion of the device loop superconductive wiring layer; and, a shield superconductive wiring layer overlying the second dielectric layer to shield at least the superconducting loop.

3. The superconducting circuit of claim 1, wherein the superconducting loop of the body of the superconducting controllable device is a superconducting qubit loop of a qubit body of a superconducting qubit.

4. The superconducting circuit of claim 3, wherein: the superconducting qubit loop of the qubit body is galvanically coupled toa Josephson junction of the superconducting qubit; the kinetic inductance layer comprises at least one pair of coupler connection leads of the qubit body, each of the at least one pair of coupler connection leads being located at a distance along a length of the first device loop conductor segment from the Josephson junction such that a majority of a total qubit inductance of the superconducting qubit is arranged therebetween; and, the superconducting circuit further comprises: at least one pair of coupler connection interfaces, each pair of coupler connection interfaces to galvanically couple a pair of coupler connection leads of the superconducting qubit to a respective pair of coupler leads of a superconducting coupler.

5. The superconducting circuit of claim 4, further comprising: a first intermediate superconductive wiring layer directly overlying at least the first dielectric layer; a second dielectric layer overlying at least a portion of the first intermediate superconductive wiring layer; a third dielectric layer overlying at least a portion of the device loop superconductive wiring layer; and, a second intermediate superconductive wiring layer overlying at least a portion of the third dielectric layer, wherein each pair of coupler connection interfaces comprises at least: a pair of first layer coupler connection portions on the first intermediate superconductive wiring layer that directly overlie a respective pair of coupler connection leads, a pair of device loop layer coupler connection portions on the device loop superconductive wiring layer that directly overlie the pair of first layer coupler connection portions, and a pair of second layer coupler connection portions on the second intermediate superconductive wiring layer that directly overlie the pair of device loop layer coupler connection portions.

6. The superconducting circuit of claim 5, wherein, for each pair of coupler connection interfaces, the pair of second layer coupler connection portions is directly galvanically couplable to the pair of coupler leads.

7. The superconducting circuit of claim 5, further comprising: a fourth dielectric layer overlying at least the second intermediate superconductive wiring layer; and, a third intermediate superconductive wiring layer directly overlying at least the fourth dielectric layer, wherein, for each pair of coupler connection interfaces: a first coupler connection interface of the pair of coupler connection interfaces includes a first one of the pair of second layer coupler connection portions that is directly galvanically couplable to a first coupler lead of the pair of coupler leads, and, a second coupler connection interface of the pair of coupler connection interfaces includes a third layer coupler connection portion on the third intermediate superconductive wiring layer directly overlying a second one of the pair of second layer coupler connection portions, the third layer coupler connection portion directly galvanically couplable to a second coupler lead of the pair of coupler leads.

8. The superconducting circuit of claim 1, further comprising: a first intermediate superconductive wiring layer overlying the first dielectric layer, the first intermediate superconductive wiring layer including one or more first bias loop conductor segments, the one or more first bias loop conductor segments located along a cross-section of the superconducting circuit to align with and overlie the first device loop conductor segment; a second dielectric layer directly overlying at least a portion of the first intermediate superconductive wiring layer; a third dielectric layer directly overlying at least a portion of the device loop superconductive wiring layer; a second intermediate superconductive wiring layer directly overlying at least the third dielectric layer, the second intermediate superconductive wiringlayer comprising one or more second bias loop conductor segments, each of the one or more second bias loop conductor segments located along the cross- section of the superconducting circuit to align with and overlie a respective one of the first bias loop conductor segments; and, a fourth dielectric layer overlying at least the second intermediate superconductive wiring layer.

9. The superconducting circuit of claim 8, wherein the body of the superconducting controllable device is symmetrical about a vertical center line along a width of the superconducting circuit.

10. The superconducting circuit of claim 8, further comprising: one or more flux bias loops, each flux bias loop surrounding a portion of a length of the second device loop conductor segment; and, an external superconductive wiring layer of the body of the superconducting controllable device comprising at least one pair of bias line interfaces, wherein each pair of bias line interfaces is directly electrically coupled to a respective flux bias loop.

11. The superconducting circuit of claim 10, wherein each of the one of more flux bias loops comprises: a plurality of superconducting vias that electrically couple a respective pair of bias line interfaces to a respective second bias loop conductor segment; and, a plurality of superconducting vias that electrically couple the respective second bias loop conductor segment to a respective first bias loop conductor segment.

12. The superconducting circuit of claim 10, wherein each of the one or more flux bias loops comprises: a respective first bias loop conductor segment of the one or more first bias loop conductor segments; first bias loop portions of the first intermediate superconductive wiring layer directly overlying the respective first bias loop conductor segment;second bias loop portions of the device loop superconductive wiring layer directly overlying the first bias loop portions; a respective second bias loop conductor segment of the one or more second bias loop conductor segments; and, third bias loop portions of the second intermediate superconductive wiring layer directly overlying the respective second bias loop conductor segment and underlying a respective pair of bias line interfaces.

13. The superconducting circuit of claim 10, wherein each pair of the at least one pair of bias line interfaces is directly electrically couplable to a respective pair of analog lines such that major axes of a first analog line and a second analog line of the respective pair of analog lines are perpendicular to major axes of the first and the second device loop conductor segments, wherein each pair of analog lines is operable to transmit a respective bias signal to the superconducting loop of the body of the superconducting controllable device.

14. The superconducting circuit of claim 1, wherein a return path electrically couples the second device loop conductor segment to the kinetic inductance layer, wherein the return path at least partially surrounds the first device loop conductor segment.

15. The superconducting circuit of claim 14, wherein the return path comprises a plurality of superconducting vias that communicatively couple the second device loop conductor segment to the first device loop conductor segment.

16. The superconducting circuit of claim 14, wherein: the kinetic inductance layer comprises first and second kinetic inductance layer return path termini located on respective first and second sides of the first device loop conductor segment along a cross-section of the superconducting circuit; and, the superconducting circuit further comprises: a first intermediate superconductive wiring layer overlying the firstdielectric layer and at least a portion of the kinetic inductance layer, and a second dielectric layer overlying at least a portion of the first intermediate superconductive wiring layer and the first dielectric layer, the device loop superconductive wiring layer overlying the second dielectric layer, wherein the return path comprises first and second intermediate layer return path portions on the first intermediate superconductive wiring layer that directly overlie the first and the second kinetic inductance layer return path termini, and the second device loop conductor segment directly overlies the first and the second intermediate return path portions for communicative coupling of the second device loop conductor segment to the kinetic inductance layer.

17. The superconducting circuit of claim 16, further comprising a shield structure, the shield structure including: a shield superconductive wiring layer on an external surface of the body of the superconducting controllable device in the superconducting circuit; and, first and second shield arms that extend from the shield superconductive wiring layer through the superconducting circuit to the first intermediate superconductive wiring layer to at least partially surround the second device loop conductor segment and the return path.

18. The superconducting circuit of claim 17, wherein the first and the second shield arms comprise superconducting vias that extend from the shield superconductive wiring layer through the superconducting circuit to the first intermediate superconductive wiring layer.

19. The superconducting circuit of claim 17, wherein: the superconducting circuit further comprises a third dielectric layer overlying at least a portion of the device loop superconductive wiring layer, and the shield superconductive wiring layer overlies the third dielectric layer and at least a portion of the device loop superconductive wiring layer; and, the first and second shield arms comprise: first and second intermediate layer shield structure portions on the first intermediate superconductive wiring layer, the first and the second intermediatelayer shield structure portions each at a respective lateral location along a width of the cross-section of the superconducting circuit, and first and second device loop layer shield structure portions on the device loop superconductive wiring layer that overlie the first dielectric layer, wherein the shield superconductive wiring layer directly overlies the first and the second device loop layer shield structure portions for communicative coupling of the shield superconductive wiring layer to the first intermediate superconductive wiring layer.

20. The superconducting circuit of claim 16, wherein: the superconducting loop of the body of the superconducting controllable device is galvanically coupled to a Josephson junction of the superconducting controllable device; the kinetic inductance layer comprises at least one pair of coupler connection leads of the body of the superconducting controllable device, each of the at least one pair of coupler connection leads located at a distance along a length of the first device loop conductor segment from the Josephson junction such that a majority of a total superconducting controllable device inductance of the superconducting controllable device is arranged therebetween; and, the superconducting circuit further comprises: at least one pair of coupler connection interfaces, each pair of coupler connection interfaces to galvanically couple a pair of coupler connection leads of the superconducting controllable device and a respective pair of coupler leads of a superconducting coupler.

21. The superconducting circuit of claim 20, further comprising: a third dielectric layer overlying at least a portion of the device loop superconductive wiring layer; and, a second intermediate superconductive wiring layer overlying at least a portion of the third dielectric layer, wherein each pair of coupler connection interfaces comprises: a pair of first layer coupler connection portions on the first intermediate superconductive wiring layer that directly overlie a respective pair of coupler connection leads,a pair of device loop layer coupler connection portions on the device loop superconductive wiring layer that directly overlie the pair of first layer coupler connection portions, and, a pair of second layer coupler connection portions on the second intermediate superconductive wiring layer that directly overlie the pair of device loop layer coupler connection portions.

22. The superconducting circuit of claim 21, wherein, for each pair of coupler connection interfaces, the pair of second layer coupler connection portions are directly galvanically couplable to the pair of coupler leads.

23. The superconducting circuit of claim 21, further comprising: a fourth dielectric layer overlying at least a portion of the second intermediate superconductive wiring layer; and, a third intermediate superconductive wiring layer overlying at least a portion of the fourth dielectric layer, wherein, for each pair of coupler connection interfaces: a first coupler connection interface of the pair of coupler connection interfaces includes a first one of the pair of second layer coupler connection portions that is directly galvanically couplable to a first coupler lead of the pair of coupler leads, and, a second coupler connection interface of the pair of coupler connection interfaces includes a third layer coupler connection portion on the third intermediate superconductive wiring layer directly overlying a second one of the pair of second layer coupler connection portions, the third layer coupler connection portion being directly galvanically couplable to a second coupler lead of the pair of coupler leads.

24. The superconducting circuit of claim 16, wherein: the first intermediate superconductive wiring layer includes one or more first bias loop conductor segments, the one or more first bias loop conductor segments located along the cross-section of the superconducting circuit to align with and overlie the first device loop conductor segment; and,the superconducting circuit further comprises: a third dielectric layer overlying at least a portion of the device loop superconductive wiring layer, a second intermediate superconductive wiring layer overlying the third dielectric layer, the second intermediate superconductive wiring layer comprising one or more second bias loop conductor segments, each of the one or more second bias loop conductor segments located along the cross-section of the superconducting circuit to align with and overlie a respective one of the first bias loop conductor segments, and, a fourth dielectric layer overlying at least a portion of the second intermediate superconductive wiring layer.

25. The superconducting circuit of claim 24, wherein the body of the superconducting controllable device is symmetrical about a vertical center line along a width of the superconducting circuit.

26. The superconducting circuit of claim 24, further comprising: one or more flux bias loops, each flux bias loop surrounding a portion of a length of the second device loop conductor segment; and, an external superconductive wiring layer of the body of the superconducting controllable device comprising at least one pair of bias line interfaces, wherein each pair of bias line interfaces is directly electrically coupled to a respective flux bias loop.

27. The superconducting circuit of claim 26, wherein each of the one or more flux bias loops comprises: a plurality of superconducting vias that electrically couple a respective pair of bias line interfaces to a respective second bias loop conductor segment; and, a plurality of superconducting vias that electrically couple the second bias loop conductor segment to a respective first bias loop conductor segment.

28. The superconducting circuit of claim 26, wherein each of the one or more flux bias loops comprises:a respective first bias loop conductor segment of the one or more first bias loop conductor segments; first bias loop portions of the first intermediate superconductive wiring layer directly overlying the respective first bias loop conductor segment; second bias loop portions of the device loop superconductive wiring layer directly overlying the first bias loop portions; a respective second bias loop conductor segment of the one or more second bias loop conductor segments; and, third bias loop portions of the second intermediate superconductive wiring layer directly overlying the respective second bias loop conductor segment.

29. The superconducting circuit of claim 26, wherein each pair of the at least one pair of bias line interfaces is directly electrically couplable to a respective pair of analog lines such that major axes of a first analog line and a second analog line of the respective pair of analog lines are perpendicular to major axes of the first and the second device loop conductor segments, wherein each pair of analog lines is to transmit a respective bias signal to the superconducting loop of the body of the superconducting controllable device.

30. The superconducting circuit of claim 1, wherein the material having a relatively high inductance value is one of: titanium nitride, niobium nitride, niobium titanium nitride, and aluminum nitride.

31. The superconducting circuit of claim 1, wherein the substrate comprises an electrically insulating material, the electrically insulating material being one of: silicon dioxide, silicon trioxide, silicon nitride, quartz, and sapphire.

32. The superconducting circuit of claim 1, wherein the relatively low inductance superconductive material comprises one of: aluminum, niobium, and tantalum.

33. The superconducting circuit of claim 1, wherein the superconducting loop of the body of the superconducting controllable device is asuperconducting coupler loop of a coupler body of a superconducting coupler.

34. The superconducting circuit of claim 1, wherein the superconducting loop of the body of the superconducting controllable device is a superconducting loop of a body of a quantum flex parametron (QFP).

35. A method of fabricating a superconducting circuit comprising: forming a kinetic inductance layer that directly overlies a substrate, the kinetic inductance layer comprising a relatively high inductance superconductive material having a relatively high inductance value and that exhibits superconducting behavior at and below a critical temperature, wherein at least a first portion of the kinetic inductance layer is a first device loop conductor segment of a superconducting loop of a body of a superconducting controllable device; forming a first dielectric layer to overlie at least a portion of the kinetic inductance layer; and, forming a device loop superconductive wiring layer to overlie the first dielectric layer, the device loop superconductive wiring layer comprising a relatively low inductance superconductive material, the relatively low inductance superconductive material having a low inductance value relative to the high inductance value and exhibiting superconducting behavior at and below a critical temperature, wherein at least a portion of the device loop superconductive wiring layer is a second device loop conductor segment of the superconducting loop.

36. The method of claim 35, wherein: the forming a kinetic inductance layer comprises: depositing the relatively high inductance superconductive material on a surface of the substrate, and patterning the deposited relatively high inductance superconductive material to include at least the first device loop conductor segment of the superconducting loop; the forming a first dielectric layer comprises at least depositing a dielectric material on a surface of the kinetic inductance layer; and, the forming a device loop superconductive wiring layer comprises:depositing the relatively low inductance superconductive material, and patterning the relatively low inductance superconductive material to include at least the second device loop conductor segment of the superconducting loop.

37. The method of claim 35, further comprising: forming a second dielectric layer through deposition of a dielectric material on at least a portion of a surface of the device loop superconductive wiring layer; and, forming a shield superconductive wiring layer through deposition of a layer of the relatively low inductance superconductive material to overlie the second dielectric layer.

38. The method of claim 35, wherein: the forming a kinetic inductance layer that directly overlies a substrate, wherein at least a first portion of the kinetic inductance layer is a first device loop conductor segment of a superconducting loop of a body of a superconducting controllable device comprises: forming the kinetic inductance layer, wherein at least the first portion of the kinetic inductance layer is a first qubit loop conductor segment of a superconducting qubit loop of a qubit body of a superconducting qubit; and, the forming a device loop superconductive wiring layer to overlie the first dielectric layer, wherein at least a portion of the device loop superconductive wiring layer is a second device loop conductor segment of the superconducting loop comprises: forming the device loop superconductive wiring layer, wherein the device loop superconductive wiring layer is a qubit loop superconductive wiring layer, and wherein at least a portion of the qubit loop superconductive wiring layer is a second qubit loop conductor segment of the qubit superconducting loop.

39. The method of claim 38, wherein: fabricating the superconducting circuit further comprises: forming a Josephson junction, wherein the Josephson junction is galvanically coupled to the superconducting qubit loop of the qubit body, and,forming one or more pairs of coupler connection interfaces; and, the forming a kinetic inductance layer comprises: depositing the high inductance superconductive material, and patterning the deposited high inductance superconductive material to include the first qubit loop conductor segment and one or more pairs of coupler connection leads of the qubit body, wherein each of the one or more pairs of coupler connection leads is patterned at a distance along a length of the first qubit loop conductor segment from the Josephson junction such that a majority of a total qubit inductance of the superconducting qubit is arranged therebetween, wherein the one or more pairs of coupler connection interfaces are to galvanically couple a respective pair of coupler connection leads of the qubit body of the superconducting qubit to a respective pair of coupler leads of a superconducting coupler.

40. The method of claim 39, further comprising: forming a first intermediate superconductive wiring layer to overlie at least a portion of the first dielectric layer; forming a second dielectric layer to overlie at least a portion of the first intermediate superconductive wiring layer; forming a third dielectric layer to overlie at least a portion of the qubit loop conductor segment superconductive wiring layer; and, forming a second intermediate superconductive wiring layer to overlie at least a portion of the third dielectric layer; wherein, to form each of the one or more pairs of coupler connection interfaces: the forming a first intermediate superconductive wiring layer comprises: depositing a second layer of the relatively low inductance superconductive material, and patterning the second layer of the relatively low inductance superconductive material to include a pair of first layer coupler connection portions that directly overlie a respective pair of coupler connection leads; the forming a qubit loop superconductive wiring layer further comprises: patterning the first layer of the relatively low inductance superconductive material to include a pair of qubit loop layer coupler connection portions that directlyoverlie the pair of first layer coupler connection portions; and, the forming a second intermediate superconductive wiring layer comprises: depositing a third layer of the relatively low inductance superconductive material, and patterning the third layer of the relatively low inductance superconductive material to include a pair of second layer coupler connection portions directly overlying the pair of qubit loop layer coupler connection portions.

41. The method of claim 40, wherein the patterning the third layer of the relatively low inductance superconductive material to include a pair of second layer coupler connection portions comprises: patterning the third layer of the relatively low inductance superconductive material to include the pair of second layer coupler connection portions, the pair of second layer coupler connection portions are directly galvanically couplable to the pair of coupler leads.

42. The method of claim 40, further comprising: forming a fourth dielectric layer to overlie at least a portion of the second intermediate superconductive wiring layer; and, forming a third intermediate superconductive wiring layer to overlie at least a portion of the fourth dielectric layer, wherein, for each pair of coupler connection interfaces: the patterning the third layer of the relatively low inductance superconductive material to include a pair of second layer coupler connection portions comprises: patterning the third layer of the relatively low inductance superconductive material to include a first one of the pair of second layer coupler connection portions that is directly galvanically couplable to a first coupler lead of the pair of coupler leads; and, the forming a third intermediate superconductive wiring layer comprises depositing a fourth layer of the relatively low inductance superconductive material, and patterning the fourth layer of the relatively low inductance superconductive material to include a third layer coupler connection portion directly overlying a second one of the pair of second layer coupler connection portions, wherein the third layer coupler connection portion is directly galvanicallycouplable to a second coupler lead of the pair of coupler leads.

43. The method of claim 35, further comprising: forming a first intermediate superconductive wiring layer to overlie the first dielectric layer, wherein the first intermediate superconductive wiring layer includes one or more first bias loop conductor segments; forming a second dielectric layer to overlie at least a portion of the first intermediate superconductive wiring layer; forming a third dielectric layer to overlie at least a portion of the device loop superconductive wiring layer; forming a second intermediate superconductive wiring layer to overlie the third dielectric layer, the forming the second intermediate superconductive wiring layer including forming one or more second bias loop conductor segments; and, forming a fourth dielectric layer to overlie at least a portion of the second intermediate superconductive wiring layer.

44. The method of claim 43, wherein: the forming a first intermediate superconductive wiring layer comprises depositing a first layer of the relatively low inductance superconductive material, and patterning the first layer of the relatively low inductance superconductive material to form each of the one or more first bias loop conductor segments at a location along a cross-section of the superconducting circuit that aligns with and overlies the first device loop conductor segment; and, the forming a second intermediate superconductive wiring layer comprises: depositing a second layer of the relatively low inductance superconductive material, and patterning the second layer of the relatively low inductance superconductive material to form each of the one or more second bias loop conductor segments at a location along the cross-section of the superconducting circuit that aligns with and overlies a respective one of the first bias loop conductor segments.

45. The method of claim 44, the method further comprising: forming an external superconductive wiring layer of the body of thesuperconducting controllable device that includes at least one pair of bias line interfaces; forming one or more flux bias loops that include at least a respective first bias loop conductor segment and a respective second bias loop conductor segment, each flux bias loop to surround a portion of a length of the second device loop conductor segment; and, wherein each pair of bias line interfaces is directly electrically coupled to a respective flux bias loop.

46. The method of claim 45, wherein forming each of the one or more flux bias loops comprises: forming a plurality of superconducting vias to electrically couple a respective pair of bias line interfaces to a respective second bias loop conductor segment; and, forming a plurality of superconducting vias to electrically couple the second bias loop conductor segment to a respective first bias loop conductor segment.

47. The method of claim 45, wherein, to form the each of the one or more flux bias loops: the forming a first intermediate superconductive wiring layer comprises: depositing a first layer of the relatively low inductance superconductive material, and patterning the first layer of the relatively low inductance superconductive material to include: a respective first bias loop conductor segment and first bias loop portions that directly overlie the first bias loop conductor segment; the forming the device loop superconductive wiring layer further comprises: depositing a second layer of the relatively low inductance superconductive material, and patterning the second layer of the relatively low inductance superconductive material to include: the second device loop conductor segment, and second bias loop portions that directly overlie the first bias loop portions; and, the forming a second intermediate superconductive wiring layer further comprises: depositing a third layer of the relatively low inductancesuperconductive material, and patterning the third layer of the relatively low inductance superconductive material to include: a respective second bias loop conductor segment, and third bias loop portions that directly overlie the respective second bias loop conductor segment and underlie a respective pair of bias line interfaces.

48. The method of claim 38, the method further comprising forming a return path that electrically couples the second device loop conductor segment of the superconducting loop to the kinetic inductance layer, wherein the return path has a relatively low inductance value and at least partially surrounds the first device loop conductor segment.

49. The method of claim 48, wherein forming the return path comprises forming a plurality of superconducting vias to communicatively couple the second device loop conductor segment to the first device loop conductor segment.

50. The method of claim 48, wherein: the forming a kinetic inductance layer comprises: depositing the relatively high inductance superconductive material, and patterning the relatively high inductance superconductive material to include: the first device loop conductor segment, and first and second kinetic inductance layer return path termini on respective first and second sides of the first device loop conductor segment along a cross-section of the superconducting circuit; the method further comprising: forming a first intermediate superconductive wiring layer, including deposition of a first layer of the relatively low inductance superconductive material, and patterning the first layer of the relatively low inductance superconductive material to include first and second intermediate layer return path portions that respectively directly overlie the first and the second kinetic inductance layer return path termini, and, forming a second dielectric layer overlying at least a portion of the first intermediate superconductive wiring layer, wherein the device loop superconductive wiring layer overlies the second dielectric layer; and,the forming a device loop superconductive wiring layer comprises: depositing a second layer of the relatively low inductance superconductive material, and patterning the second layer of the relatively low inductance superconductive material to include the second device loop conductor segment, wherein the second device loop conductor segment directly overlies the first and the second intermediate return path portions.

51. The method of claim 50, further comprising forming a shield structure, the forming the shield structure including: forming a shield superconductive wiring layer on an external surface of the body of the superconducting controllable device in the superconducting circuit; and, forming first and second shield arms that at least partially surround the second device loop conductor segment and the return path.

52. The method of claim 51, wherein the forming first and second shield arms comprises forming superconducting vias that extend from the shield superconductive wiring layer through the superconducting circuit to the first intermediate superconductive wiring layer.

53. The method of claim 51, further comprising: forming a third dielectric layer overlying at least a portion of the of the device loop superconductive wiring layer; and, and wherein to form the first and the second shield arms: the forming a first intermediate superconductive wiring layer further comprises patterning the first layer of the relatively low inductance superconductive material to include first and second intermediate layer shield structure portions, each at a respective lateral location along a width of the cross- section of the superconducting circuit, the forming a device loop superconductive wiring layer further comprises patterning the second layer of the relatively low inductance superconductive material to include first and second device loop layer shield structure portions that respectively directly overlie the first and the second intermediate layer shieldstructure portions, and, the forming a shield superconductive wiring layer comprises depositing a shield layer of the relatively low inductance superconductive material that directly overlies at least the first and the second device loop layer shield structure portions.

54. The method of claim 52, wherein: fabricating the superconducting circuit further comprises: forming a Josephson junction, wherein the Josephson junction is galvanically coupled to the superconducting loop of the body of the superconducting controllable device, and, forming one or more pairs of coupler connection interfaces; and, the forming a kinetic inductance layer further comprises patterning the high inductance superconductive material to include one or more pairs of coupler connection leads of the body of the superconducting controllable device, each of the one or more pairs of coupler connection leads patterned on the kinetic inductance layer at a distance along a length of the first device loop conductor segment from the Josephson junction such that a majority of a total inductance of the superconducting controllable device is arranged therebetween, wherein the one or more pairs of coupler connection interfaces are to galvanically couple a respective pair of coupler connection leads of the body of the superconducting controllable device to a respective pair of coupler leads of a superconducting coupler.

55. The method of claim 54, further comprising: forming a fourth dielectric layer to overlie at least a portion of the device loop superconductive wiring layer; and, forming a second intermediate superconductive wiring layer to overlie at least a portion of the fourth dielectric layer; wherein, to form each of the one or more pairs of coupler connection interfaces: the forming a first intermediate superconductive wiring layer comprises: depositing a second layer of the relatively low inductance superconductivematerial, and patterning the second layer of the relatively low inductance superconductive material to include a pair of first layer coupler connection portions that directly overlie a respective pair of coupler connection leads; the forming a device loop superconductive wiring layer further comprises: patterning the first layer of relatively low inductance superconductive material to include a pair of device loop layer coupler connection portions that directly overlie the pair of first layer coupler connection portions; and, the forming a second intermediate superconductive wiring layer comprises: depositing a third layer of the relatively low inductance superconductive material, and patterning the third layer of the relatively low inductance superconductive material to include a pair of second layer coupler connection portions directly overlying the pair of device loop layer coupler connection portions.

56. The method of claim 55, wherein the patterning the third layer of the relatively low inductance superconductive material to include a pair of second layer coupler connection portions comprises patterning the third layer of the relatively low inductance superconductive material to include a pair of second layer coupler connection portions that are directly galvanically couplable to the pair of coupler leads.

57. The method of claim 55, further comprising: forming a fourth dielectric layer to overlie at least a portion of the second intermediate superconductive wiring layer; and, forming a third intermediate superconductive wiring layer to overlie at least a portion of the fourth dielectric layer, wherein, to form each of the one or more pairs of coupler connection interfaces: the patterning the third layer of the relatively low inductance superconductive material to include a pair of second layer coupler connection portions comprises patterning the third layer of the relatively low inductance superconductive material to include a first one of the pair of second layer coupler connection portions that is directly galvanically couplable to a first coupler lead ofthe pair of coupler leads; and, the forming a third intermediate superconductive wiring layer comprises depositing a fourth layer of the relatively low inductance superconductive material, and patterning the fourth layer of the low relatively inductance superconductive material to include a third layer coupler connection portion directly overlying a second one of the pair of second layer coupler connection portions, wherein the third layer coupler connection portion is directly galvanically couplable to a second coupler lead of the pair of coupler leads.

58. The method of claim 53, wherein: the forming a first intermediate superconductive wiring layer further comprises patterning the first layer of the relatively low inductance superconductive material to include one or more first bias interface loop conductor segments, each of the one or more first bias loop conductor segments at a location along a cross-section of the superconducting circuit that aligns with and overlies the first device loop conductor segment; and, the method further comprising: forming a second intermediate superconductive wiring layer to overlie the third dielectric layer, wherein the forming the second intermediate superconductive wiring layer includes: deposition of a third layer of the relatively low inductance superconductive material, and patterning the third layer of the relatively low inductance superconductive material to include one or more second bias loop conductor segments, each of the one or more second bias loop conductor segments at a location along the cross-section of the superconducting circuit that aligns with and overlies a respective one of the first bias loop conductor segments, and forming a fourth dielectric layer to overlie at least a portion of the second intermediate superconductive wiring layer.

59. The method of claim 58, the method further comprising: forming an external superconductive wiring layer of the body of the superconducting controllable device that includes at least one pair of bias line interfaces; and,forming one or more flux bias loops that include at least a respective first bias loop conductor segment and a respective second bias loop conductor segment, each flux bias loop to surround a portion of a length of the second device loop conductor segment, wherein each pair of bias line interfaces is directly galvanically coupled to a respective flux bias loop.

60. The method of claim 59, wherein forming each of the one or more flux bias loops comprises: forming a plurality of superconducting vias to electrically couple a respective pair of bias line interfaces to a respective second bias loop conductor segment; and, forming a plurality of superconducting vias to electrically couple the second bias loop conductor segment to a respective first bias loop conductor segment.

61. The method of claim 59, wherein to form the each of the one or more flux bias loops: the forming a first intermediate superconductive wiring layer further comprises patterning the first layer of the relatively low inductance superconductive material to include: a respective first bias loop conductor segment and first bias loop portions that directly overlie the first bias loop conductor segment; the forming a device loop superconductive wiring layer further comprises patterning the second layer of the relatively low inductance superconductive material to include second bias loop portions that directly overlie the first bias loop portions; and, the forming a second intermediate superconductive wiring layer further comprises patterning the third layer of the relatively low inductance superconductive material to include: a respective second bias loop conductor segment, and third bias loop portions that directly overlie the respective second bias loop conductor segment and underlie a respective pair of bias line interfaces.

62. The method of claim 35, wherein the forming a kinetic inductance layer comprises forming the kinetic inductance layer from one of: titanium nitride, niobium nitride, niobium titanium nitride, and aluminum nitride.

63. The method of claim 35, wherein the forming a superconductive loop layer comprises forming the superconductive wiring layer from one of: aluminum, niobium, and tantalum.

64. The method of claim 35, wherein: the forming a kinetic inductance layer that directly overlies a substrate, wherein at least a first portion of the kinetic inductance layer is a first device loop conductor segment of a superconducting loop of a body of a superconducting controllable device comprises: forming the kinetic inductance layer, wherein at least the first portion of the kinetic inductance layer is a first coupler loop conductor segment of a superconducting coupler loop of a coupler body of a superconducting coupler; and, the forming a device loop superconductive wiring layer to overlie the first dielectric layer, wherein at least a portion of the loop superconductive wiring layer is a second device loop conductor segment of the superconducting loop comprises: forming the loop superconductive wiring layer, wherein at least a portion of the coupler loop superconductive wiring layer is a second coupler loop conductor segment of the coupler superconducting loop.

65. The method of claim 35, wherein: the forming a kinetic inductance layer that directly overlies a substrate, in which at least a first portion of the kinetic inductance layer is a first device loop conductor segment of a superconducting loop of a body of a superconducting controllable device comprises: forming the kinetic inductance layer, in which the first loop conductor segment is a portion of a superconducting body loop of a quantum flux parametron (QFP); the forming a device loop superconductive wiring layer to overlie the first dielectric layer, wherein at least a portion of the device loop superconductive wiring layer is a second device loop conductor segment of the superconductingloop comprises: forming the device loop superconductive wiring layer, wherein the second device loop conductor segment is a second portion of the superconducting body loop of the QFP.

66. A superconducting qubit comprising: a qubit body comprising a superconducting qubit loop that includes a first qubit loop conductor segment communicatively coupled to a second qubit loop conductor segment, wherein the first qubit loop conductor segment comprises a relatively high inductance superconductive material that has a relatively high inductance value and exhibits superconducting behavior at and below a critical temperature, and the second qubit loop conductor segment comprises a relatively low inductance superconductive material that has a relatively low inductance value in comparison to the relatively high inductance value of the relatively high inductance superconductive material and exhibits superconducting behavior at and below a critical temperature, wherein the second qubit loop conductor segment overlies the first qubit loop conductor segment within at least a portion of a superconducting circuit that comprises the superconducting qubit; and, a Josephson junction electrically coupled to the superconducting qubit loop of the qubit body.

67. The superconducting qubit of claim 66, wherein the qubit body further comprises a shield structure that at least partially surrounds the superconducting qubit loop, the shield structure including at least a planar shield portion on an external surface of the qubit body that overlies the second qubit loop conductor segment in the at least a portion of the superconducting circuit, and the planar shield portion comprising the relatively low inductance superconductive material.

68. The superconducting qubit of claim 67, wherein the shield structure further comprises a pair of shield arms, each one of the pair of shield arms extending from the planar shield portion into the at least a portion of the superconducting circuit to at least partially surround the second qubit loop conductor segment, wherein the shield arms comprise the relatively lowinductance superconductive material.

69. The superconducting qubit of claim 66, wherein the qubit body further comprises a return path extending from the second qubit loop conductor segment to return path termini, the return path termini comprising the relatively high inductance superconductive material and located on a same layer of the at least a portion of the superconducting circuit as the first qubit loop conductor segment such that the return path at least partially surrounds the first qubit loop conductor segment, and wherein at least a majority of the return path comprises the relatively low inductance superconductive material.

70. The superconducting qubit of claim 66, wherein: the first qubit loop conductor segment comprises one or more pairs of coupler connection leads; and, the qubit body further comprises one or more pairs of coupler connection interfaces, each of the one or more pairs of coupler connection interfaces configured to galvanically couple a pair of the one or more pair of coupler connection leads to a respective pair of coupler leads of a superconducting coupler.

71. The superconducting qubit of claim 70, wherein each one of the one or more pairs of coupler connection leads is located at a distance along a length of the qubit body from the Josephson junction such that a majority of a total qubit inductance of the superconducting qubit is arranged therebetween.

72. The superconducting qubit of claim 70, wherein each one of the one or more pairs of coupler connection interfaces of the qubit body comprises a first coupler connection interface and a second coupler connection interface, the first and second coupler connection interface respectively extending through the at least a portion of the superconducting circuit from a first and a second coupler connection lead of a respective pair of coupler connection leads to a first and a second coupler connection site of the qubit body, the first and the second coupler connection site located on a same layer of the at least a portion of thesuperconducting circuit that overlies the second qubit loop conductor segment, and wherein the first and the second coupler connection interface comprise the relatively low inductance superconductive material.

73. The superconducting qubit of claim 70, wherein each one of the one or more pairs of coupler connection interfaces comprises: a first coupler connection interface, the first coupler connection interface extending through the at least a portion of the superconducting circuit from a first coupler connection lead of a respective pair of coupler connection leads to a first coupler connection site of the qubit body at which the first coupler connection interface is galvanically couplable to a first coupler lead of a respective pair of coupler leads, the first coupler connection site overlying the second qubit loop conductor segment; and, a second coupler connection interface, the second coupler connection interface extending through the at least a portion of the superconducting circuit from a second coupler connection lead of the pair of coupler connection leads to a second coupler connection site of the qubit body at which the second coupler connection interface is galvanically couplable to a second coupler lead of the pair of coupler leads, the second coupler connection site overlying the first coupler connection site, wherein the first and the second coupler connection interface comprise the relatively low inductance superconductive material.

74. The superconducting qubit of claim 66, wherein the qubit body further comprises one or more bias connection interfaces, wherein each bias connection interface is to electrically couple the superconducting qubit loop to a respective pair of analog lines that transmit a bias signal, each bias connection interface comprising: a first bias loop conductor segment that interposes the first qubit loop conductor segment and the second qubit loop conductor segment, wherein the first bias loop conductor segment is aligned with the first qubit loop conductor segment along a width of the at least a portion of the superconducting circuit;and, a second bias loop conductor segment that overlies the second qubit loop conductor segment, wherein the second bias loop conductor segment is aligned with the first bias loop conductor segment along the width of the at least a portion of the superconducting circuit.

75. The superconducting qubit of claim 74, wherein each one of the one or more bias connection interfaces comprises: a pair of bias line interfaces on an external surface of the qubit body in the superconducting circuit that overlies the second qubit loop conductor segment, wherein the pair of bias line interfaces are directly electrically couplable to a respective pair of analog lines; and, a flux bias loop of the qubit body that surrounds a portion of a length of the second qubit loop conductor segment, the flux bias loop including the first and the second bias loop conductor segment, and wherein the flux bias loop galvanically couples the first bias loop conductor segment, the second bias loop conductor segment, and the pair of bias line interfaces, wherein the pair of bias line interfaces and the flux bias loop comprise the relatively low inductance superconductive material.

76. The superconducting qubit of claim 75, wherein the pair of bias line interfaces are directly communicatively couplable to a respective pair of analog lines such that major axes of first and the second analog lines of the respective pair of analog lines are perpendicular to major axes of the first and the second qubit loop conductor segments.

77. The superconducting qubit of claim 74, wherein an external surface of the qubit body in the at least a portion of the superconducting circuit further comprises at least a portion of a shield structure, the shield structure comprising the relatively low inductance superconductive material.

78. The superconducting qubit of claim 66, wherein the superconducting qubit is symmetrical about a vertical center line along a width ofthe qubit body.

79. The superconducting qubit of claim 66, wherein the relatively high inductance superconductive material comprises one of: titanium nitride, niobium nitride, niobium titanium nitride, and aluminum nitride.

80. The superconducting qubit of claim 66, wherein the relatively low inductance superconductive material comprises one or more of: aluminum, niobium, and tantalum.

81. The superconducting qubit of claim 66, wherein an inductance per unit length of the relatively high inductance superconductive material is 50 times greater than an inductance per unit length of the relatively low inductance superconductive material.

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