Precision ferrite-based electromagnetic signal circulator for quantum computing systems

Abstract

The present disclosure relates to a waveguide assembly within a non-reciprocal electronic device (e.g., a circulator). The waveguide assembly may include a ferrite member, a magnetic member, and a pole assembly. The pole assembly forms a magnetic circuit in combination with at least the ferrite member and the magnetic member. The magnetic pole assembly has spatial variation of magnetic resistance. The spatial variation in the reluctance of the pole assembly provides an increase in the uniformity of the magnetic flux throughout the volume of the ferrite member. Due to the increase in the uniformity of the magnetic flux throughout the entire volume of the ferrite member, the non-reciprocity properties of the electronic device are enhanced.

Description

[0001] CLAIM OF PRIORITY

[0002] This application is based on and claims priority to U.S. Provisional Application 18 / 332,455, filed June 9, 2023, which is incorporated by reference herein. TECHNICAL FIELD

[0003] The present disclosure relates generally to quantum computing systems, and more particularly to precision ferrite-based microwave and radio frequency signal circulators employable in quantum computing systems. BACKGROUND

[0004] Quantum computing is a method of computing that leverages quantum effects, such as superposition of states and entanglement, to perform certain computations more efficiently than classical digital computers. Unlike digital computers, which store and manipulate information in the form of bits (e.g., “1” or “0”), quantum computing systems can use qubits to manipulate information. A qubit can refer to a quantum device that is capable of superposition of multiple states (e.g., data in both “0” and “1” states), and / or to the superposition of data itself in multiple states. According to conventional terminology, the superposition of “0” and “1” states in a quantum system can be represented as, for example, + b The “0” and “1” states of a digital computer are analogous to the and ground states of a qubit, respectively. SUMMARY

[0005] Aspects and advantages of embodiments of the present disclosure will be set forth in part in the following description, or can be obvious from the description, or can be learned through practice of the embodiments.

[0006] One example aspect of the present disclosure relates to a waveguide assembly within a non-reciprocal electronic device (e.g., a circulator). The waveguide assembly can include a ferrite member, a magnetic member, and a pole assembly. The pole assembly, in combination with at least the ferrite member and the magnetic member, forms a magnetic circuit. The pole assembly has a spatial variation of magnetic reluctance. The spatial variation of the magnetic reluctance of the pole assembly provides an increase in uniformity of magnetic flux throughout a volume of the ferrite member. As a result of the increase in the uniformity of the magnetic flux throughout the volume of the ferrite member, the non-reciprocal properties of the electronic device are enhanced.

[0007] Other aspects of the present disclosure relate to various systems, methods, apparatuses, non-transitory computer-readable media, computer-readable instructions, and computing devices.

[0008] These and other features, aspects, and advantages of various embodiments of the present disclosure will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate example embodiments of the present disclosure and, together with the description, explain related principles. BRIEF DESCRIPTION OF DRAWINGS

[0009] With reference to the accompanying drawings, a detailed discussion of embodiments oriented to one of ordinary skill in the art is set forth in the present specification, in which:

[0010] FIG. 1 An example quantum computing system is depicted in accordance with example embodiments of the present disclosure.

[0011] FIG. 2A A schematic diagram of an example circulator including a waveguide assembly is depicted in accordance with example embodiments of the present disclosure.

[0012] FIG. 2B An exploded view of a waveguide assembly of FIG. 2A is depicted in accordance with example embodiments of the present disclosure.

[0013] FIGS. 3A-3F Example embodiments of pole assemblies and pole members having example, but non-limiting, discontinuous and continuous spatial variations in thickness and permeability are depicted.

[0014] FIGS. 4A-4C Example embodiments of pole assemblies and pole members having example, but non-limiting, discontinuous and continuous spatial variations in thickness and permeability are depicted.

[0015] FIGS. 5A-5B Example embodiments of pole assemblies and pole members having example, but non-limiting, discontinuous and continuous spatial variations in thickness and permeability are depicted.

[0016] FIGS. 6A-6B Example embodiments of pole assemblies and pole members having example, but non-limiting, discontinuous and continuous spatial variations in thickness and permeability are depicted. DETAILED DESCRIPTION

[0017] Example aspects of the present disclosure relate to precision ferrite-based circulators for microwave signals and / or radio frequency electromagnetic (EM) signals. The precision circulators of these embodiments can be used in quantum computing systems. More specifically, the circulators can be used to route and / or isolate microwave (μwave) and / or radio frequency (RF) signals generated in quantum computing systems (e.g., qubit control and / or qubit readout signals). The precision circulators of embodiments can operate within cryogenic systems (e.g., within a quantum computer) or other μwave or RF systems that require signal routing and / or signal isolation by the circulators. One general property of the circulators of embodiments includes non-reciprocal signal routing and signal isolation. Such non-reciprocal devices provide an asymmetry in the direction of flow of EM signals. The asymmetry in the directional flow of signals provides precision routing and isolation of signals.

[0018] At least some of the embodiments relate to ferrite-based circulators. As discussed below, the ferrite-based circulators achieve non-reciprocal routing and / or isolation of input signals (e.g., μwave or RF waves) via EM interaction between the input signals and an approximately time-invariant and uniform magnetic field within the circulator. As discussed below, deviations in the uniformity of the magnetic field can degrade the performance of the circulator. As used herein, a uniform magnetic field describes (at least approximate) spatial uniformity of the magnetic flux density of the magnetic field throughout the ferrite member of the circulator.

[0019] Accordingly, embodiments relate to precisely controlling the shape and / or uniformity of the magnetic field within the circulator. Traditional methods of controlling the uniformity and shape of the magnetic field within the circulator can fail when scaled to the requirements of some μwave or RF wave systems (e.g., cryogenic systems and / or quantum computing systems). In embodiments, the waveguide assembly included in the circulator includes a magnetic circuit having one or more magnetic members, one or more pole assemblies, and one or more ferrite members. Via the one or more magnetic members, a magnetic field is generated throughout the magnetic circuit (including within the one or more ferrite members). The magnetic field within the ferrite member is used to polarize (or bias) the ferrite member. Embodiments include precisely controlling the shape and / or uniformity of the magnetic field within the magnetic circuit (including the one or more ferrite members) by varying the reluctance within the one or more pole assemblies as a function of position. That is, in embodiments, the uniformity of the magnetic flux density throughout the ferrite member is increased via the design and placement of the pole assemblies. More specifically, the increase in the uniformity of the magnetic flux density (within the ferrite member) is achieved by spatially varying the reluctance in the pole assemblies. The spatial variation in the reluctance within the pole assemblies is primarily achieved by spatially varying the reluctance of the one or more pole members included in the pole assemblies.

[0020] The magnetic pole assembly can include one or more magnetic pole members. The magnetic pole members can be 3D objects such as, but not limited to, cylindrical disks (e.g., circular or elliptical cylinders). Although embodiments are not limited in this regard, the magnetic pole members can take other 3D shapes such as, but not limited to, spheres, ellipsoids, parallelepipeds, or other such shapes. The magnetic pole members can be irregularly shaped. The aspect ratio of a cylindrical (circular or elliptical) disk can be defined as the ratio of the vertical height (or thickness) of the cylindrical disk to its diameter (or the major or minor axis of an elliptical disk). In various embodiments, the cylindrical disk can have an aspect ratio that is less than 1.0. In some embodiments, the aspect ratio of the cylindrical disk can be substantially less than 1.0.

[0021] Varying at least one of the shape or the magnetic permeability of the magnetic pole members spatially as a function of the position on the surface of the magnetic pole members can enable a change in the magnetic reluctance of the magnetic pole assembly. For example, the shape (e.g., as measured from the side profile) of a magnetic pole member can be changed by varying the thickness (e.g., height) of the magnetic pole member as a function of the position on the top (or bottom) surface of the cylindrical disk magnetic pole member. The thickness of the magnetic pole member can be measured along a vertical direction. It should be noted that in various embodiments, the vertical direction can be defined as substantially parallel to the main direction of the magnetic field (generated by the magnetic member) that penetrates the volume of the magnetic pole member. That is, when both the magnetic member and the magnetic pole member are positioned within the magnetic circuit of the waveguide, the vertical direction that defines the thickness of the magnetic pole member is primarily aligned with the magnetic dipole of the magnetic member. The thickness (or shape) of the magnetic pole member can be varied by various discrete objects included by the top and / or bottom of the magnetic pole member such as, but not limited to, voids (e.g., perforations), etchings, recesses, protrusions, etc. on one or more surfaces of the magnetic pole member. For example, in the location of a void (e.g., hole), the thickness of the magnetic pole member can be 0.0, while in the location of no void, the thickness of the magnetic pole member can be non-zero. The etchings can be fabricated via an electrochemical etching process. The various discrete objects can have uniform or non-uniform geometry. The pattern of the discrete objects can be a regular and / or symmetric pattern about one or more rotation and / or reflection axes. In other embodiments, the pattern of the discrete objects can be an irregular and / or asymmetric pattern. In some embodiments, the thickness can be varied at least to some extent continuously via a continuous gradient of the thickness of the magnetic pole member.

[0022] The magnetic permeability of the pole member can be varied in a similar discrete and / or continuous manner. For example, the pole member can be composed of multiple materials, each material having a separate magnetic permeability. By varying the placement of the separate materials, the magnetic permeability of the pole member can be varied as a function of the location within the pole member. A pole member composed of more than one material can be referred to as a composite pole member. Similar to the spatial variation of the shape of the pole member, the spatial variation of the magnetic permeability of the pole member can be symmetric or asymmetric. The spatial variation of both the shape (e.g., thickness) and the magnetic permeability can be combined within a single pole member.

[0023] The spatial variation of the shape and / or the magnetic permeability of the pole member can be described as a gradient in the pole member. The gradient can be a thickness gradient, as the thickness of the pole member varies spatially. The gradient can be a magnetic permeability gradient, as the thickness of the pole member varies spatially. It is noted that both the thickness gradient and the magnetic permeability gradient can be continuous or discontinuous. An example of a discontinuous gradient can include various discrete objects on one or more surfaces of the pole member, such as, but not limited to, voids, recesses, protrusions, etc.

[0024] By spatially varying the reluctance of the pole member, the non-uniformity associated with one or more magnets (of the magnetic circuit) can be compensated. That is, the deviation of the non-uniformity of the magnetic field can be compensated by the spatial variation of the magnetic permeability and / or shape (e.g., thickness) of the pole member. In the presence of a pole member having a spatial variation of the magnetic permeability and / or thickness, the non-uniform magnetic field provided by the one or more magnets is shaped to be sufficiently uniform throughout the ferrite member in order to accurately route and / or isolate signals.

[0025] The circulator of embodiments includes a waveguide assembly that functions as a waveguide having non-reciprocal behavior. The waveguide assembly includes at least one magnet (e.g., a magnetic member), at least one pole assembly (e.g., including at least a pole member), and at least one ferrite member. The magnet, the pole assembly, and the ferrite member form a magnetic circuit within the waveguide assembly. The magnetic field of the magnet polarizes (or biases) the ferrite member. When an input EM signal interacts with the polarized ferrite member, the signal experiences Faraday rotation. Faraday rotation is essentially a rotation (e.g., by 45°) of the polarization plane of the EM signal. Via the waveguide (e.g., resonator, transmission line, etc.) and the rotation of the polarization plane, the circulator provides non-reciprocal transmission of the EM signal. Deviation of the uniform magnetic field reduces the ability of the ferrite material to provide accurate Faraday rotation of the polarization plane of the EM signal. Thus, the non-uniform magnetic field reduces the non-reciprocal signal routing and signal isolation capabilities of the circulator.

[0026] The pole member (or pole piece) is included in one or more pole assemblies. The one or more pole assemblies are disposed proximate to one or more magnets (e.g., permanent magnets) within the waveguide assembly. The pole member is composed of a high magnetic permeability material for shaping the magnetic field generated by the magnets. To precisely control this magnetic flux density of the magnetic field within the ferrite member and throughout the magnetic circuit and ensure the desired shape and / or uniformity of the magnetic field, the shape and / or permeability of the pole assembly can be spatially varied. By spatially varying the shape and / or permeability of the pole member, the reluctance within the pole member (and thus the pole assembly) spatially varies when the pole assembly is positioned within the magnetic circuit. By spatially varying the reluctance of one or more members within the pole assembly (as a function of position), the resulting shape and / or uniformity of this magnetic flux density of the magnetic field within the magnetic circuit (including within the ferrite member) can be precisely controlled.

[0027] Generally, a circulator is a passive electronic device with three (or more) signal ports (or signal terminals). The circulator is designed to deterministically route an input electromagnetic signal (e.g., a μwave or RF) from one of the ports to another. The circulator typically operates on the principle of non-reciprocity, which means that the signal flow between the ports is asymmetric. For example, in a three-port (or terminal) circulator, the ports can be labeled as port 1, port 2, and port 3. When a signal is applied to port 1, the circulator allows the signal to pass through to port 2 while providing high isolation between port 2 and port 3. This means that signals can flow from port 1 to port 2, but they are actually prevented from reaching port 3. If a signal is applied to port 2, the circulator routes the signal to port 3 while maintaining high isolation between port 1 and port 3. Thus, signals can travel from port 2 to port 3, but they are isolated and prevented from reaching port 1. A key property of the circulator is its ability to provide isolation between the ports. This means that signals entering one port are largely prevented from leaking or interfering with signals at the other ports. The degree of isolation determines the effectiveness of signal separation. The circulators of embodiments can be used in quantum computing systems. However, embodiments are not limited as such, and the circulators disclosed herein can be used in a variety of applications, including but not limited to radar systems, telecommunications networks, satellite communications, and other RF and / or μwave systems. The various circulators disclosed herein help control signal flow, prevent signal reflections, and improve overall system performance by reducing interference and isolating different components within the system. Although the discussion herein focuses on 3-port circulators, embodiments are not limited as such, and can be readily extended to circulators with any number of ports greater than three.

[0028] Embodiments relate to ferrite circulators. Ferrite circulators require a uniform magnetic field to provide precise signal routing and signal isolation. The presence of a uniform magnetic field is necessary for the functioning of the ferrite material within the circulator. The ferrite component is composed of a ferrite material, such as but not limited to an iron oxide compound. The ferrite material can exhibit a property known as “gyromagnetic resonance” or “ferrimagnetic resonance.” That is, the ferrite material can absorb and emit microwave energy under the influence of a magnetic field. In order to achieve the above-discussed non-reciprocal behavior of the circulator, a bias magnetic field is applied to the ferrite material within the circulator. The bias magnetic field can be provided by a magnetic component. This magnetic field aligns the magnetic moments within the ferrite component, allowing the desired gyromagnetic resonance behavior to be achieved. The uniformity of this magnetic field is critical to the consistent and predictable non-reciprocal behavior of the circulator.

[0029] When an EM signal enters the waveguide assembly of the circulator, the signal interacts with the ferrite material (via EM forces). The uniform magnetic field enables the ferrite material to absorb a portion of the energy of the signal and re-emit it in a particular direction (e.g., via Faraday rotation of the polarization plane of the signal). The non-reciprocal behavior ensures that the signal is routed to the appropriate output port while minimizing reflections and interference among the multiple signals provided to and / or by the various ports. The pole component of embodiments controls the distribution (e.g., shape and uniformity) of the magnetic field. That is, by spatially varying the shape and permeability of the pole component, the pole component shapes and concentrates the magnetic field within the ferrite component.

[0030] Aspects of the present disclosure provide a variety of technical effects and benefits. For example, the pole component (with various gradients) helps to direct and focus the magnetic field within the ferrite component. This can provide: concentration of the magnetic field within a desired region, thereby optimizing the performance of the circulator. The pole component of embodiments provides improved signal isolation. By spatially varying the shape and / or permeability of the pole component, the pole component can enhance the isolation between the input and output ports of the circulator. By directing the magnetic field in a particular manner, the pole component suppresses unwanted signal reflections and improves the isolation performance of the circulator. The pole component of embodiments helps to reduce magnetic field leakage, which can result in losses in the circulator. By shaping and directing the magnetic field, the pole component helps to reduce or minimize leakage of the magnetic field outside of the ferrite material, thereby reducing insertion loss and improving overall efficiency. By spatially varying the shape and / or permeability of the pole component, the operational bandwidth of the circulator can be increased (or reduced as desired within the particular application of the circulator). Thus, the pole component of embodiments improves the performance characteristics of the circulator (and other non-reciprocal devices), such as but not limited to isolation, insertion loss, efficiency, and bandwidth.

[0031] FIG. 1An example quantum computing system 100 is depicted. System 100 is an example of a system of one or more classical computers and / or quantum computing devices located in one or more locations in which the systems, components, and techniques described below can be implemented. Using the disclosure provided herein, those of ordinary skill in the art will appreciate that other quantum computing devices or systems can be used without departing from the scope of the present disclosure.

[0032] System 100 includes quantum hardware 102 in data communication with one or more classical processors 104. Classical processor 104 can be configured to execute computer-readable instructions stored in one or more memory devices to perform operations, such as any of the operations described herein. Quantum hardware 102 includes components for performing quantum computations. For example, quantum hardware 102 includes a quantum system 110, a control device 112, and a readout device 114 (e.g., a readout resonator). Quantum system 110 can include one or more multi-level quantum subsystems, such as a register of qubits (e.g., qubit 120). In some implementations, the multi-level quantum subsystems can include superconducting qubits, such as flux qubits, charge qubits, transmon qubits, gmon qubits, spin-based qubits, and the like.

[0033] The type of multi-level quantum subsystems used by system 100 can vary. For example, in some cases, it can be convenient to include one or more readout devices 114 attached to one or more superconducting qubits (e.g., transmon qubits, flux qubits, gmon qubits, xmon qubits, or other qubits). In other cases, ion traps, photonic devices, or superconducting cavities can be used (e.g., with which it can not be necessary to prepare states using qubits). Additional examples of implementations of multi-level quantum subsystems include fluxmon qubits, silicon quantum dots, or phosphorus quantum dots.

[0034] A quantum circuit can be constructed and applied to a register of qubits included in quantum system 110 via a plurality of control lines coupled to one or more control devices 112. An example control device 112 operating on a register of qubits can be used to implement a quantum gate or a quantum circuit having a plurality of quantum gates, such as a Pauli gate, an Hadamard gate, a controlled not (CNOT) gate, a controlled phase gate, a T gate, a multi-qubit quantum gate, a coupler quantum gate, and the like. One or more control devices 112 can be configured to operate on quantum system 110 by one or more respective control parameters (e.g., one or more physical control parameters). For example, in some implementations, the multi-level quantum subsystems can be superconducting qubits, and control device 112 can be configured to provide control pulses to the control lines to produce a magnetic field to adjust the frequency of the qubits.

[0035] Quantum hardware 102 may further include a readout device 114 (e.g., a readout resonator). Measurement results 108 obtained via the measurement device can be provided to classical processor 104 for processing and analysis. In some implementations, quantum hardware 102 may include quantum circuits, and control device 112 and readout device 114 may implement one or more quantum logic gates that operate the quantum system 102 via physical control parameters (e.g., microwave pulses) transmitted via wires included in quantum hardware 102. Further examples of the control device include an arbitrary waveform generator, where a DAC (digital-to-analog converter) creates the signal.

[0036] The readout device 114 can be configured to perform a quantum measurement on the quantum system 110 and send the measurement result 108 to the classical processor 104. Additionally, the quantum hardware 102 can be configured to receive data from the classical processor 104 specifying physical control qubit parameter values ​​106. The quantum hardware 102 can use the received physical control qubit parameter values ​​106 to update the actions of the control device 112 and the readout device 114 on the quantum system 110. For example, the quantum hardware 102 can receive data specifying a new value representing the voltage intensity of one or more DACs included in the control device 112, and the quantum hardware can update the actions of the DACs on the quantum system 110 accordingly. The classical processor 104 can be configured, for example, to initialize the quantum system 110 in an initial quantum state by sending data specifying an initial parameter set 106 to the quantum hardware 102.

[0037] In some implementations, the readout device 114 may utilize the elements of a quantum system (such as qubits). and The impedance difference of a state is used to measure the state of an element (e.g., a qubit). For example, due to the nonlinearity of a qubit, when a qubit is in a state... or state The resonant frequency of the readout resonator can be different. Therefore, the microwave pulse reflected from the readout device 114 carries an amplitude and phase shift depending on the qubit state. In some implementations, a Purcell filter can be used in conjunction with the readout device 114 to block microwave propagation at the qubit frequency.

[0038] In some embodiments, the quantum system 110 may include, for example, a plurality of qubits 120 arranged in a two-dimensional grid 122. For clarity, FIG. 1The depicted two-dimensional grid 122 includes 4x4 qubits, however in some implementations, the system 110 can include a lesser or greater number of qubits. In some embodiments, the plurality of qubits 120 can interact with one another through a plurality of qubit couplers (e.g., qubit coupler 124). The qubit couplers can define nearest-neighbor interactions between the plurality of qubits 120. In some implementations, the strength of the plurality of qubit couplers is a tunable parameter. In some cases, the plurality of qubit couplers included in the quantum computing system 100 can be couplers with fixed coupling strengths.

[0039] In some implementations, the plurality of qubits 120 can include data qubits (such as qubit 126) and measurement qubits (such as qubit 128). Data qubits are qubits that participate in computations performed by the system 100. Measurement qubits are qubits that can be used to determine the results of computations performed by the data qubits. That is, during a computation, the unknown state of a data qubit is transferred to a measurement qubit using an appropriate physical operation, and measured via an appropriate measurement operation performed on the measurement qubit.

[0040] In some implementations, each qubit in the plurality of qubits 120 can be operated using a respective operating frequency, such as an idle frequency and / or an interaction frequency and / or a readout frequency and / or a reset frequency. The operating frequencies of different qubits can be different. For example, each qubit can idle at a different operating frequency. The operating frequencies of the qubits 120 can be selected prior to performing a computation.

[0041] FIG. 1 One example quantum computing system that can be used to implement methods and operations in accordance with example aspects of the present disclosure is depicted. Other quantum computing systems can be used without departing from the scope of the present disclosure.

[0042] FIG. 2A A schematic diagram of an example circulator 200 is depicted in accordance with various embodiments. FIG. 2A The view of the circulator 200 in FIG. 1 is a top view. The circulator includes a first terminal 202 (or first port), a second terminal 204 (or second port), and a third terminal 206 (or third port), and a waveguide assembly 210. In conjunction with FIG. 2B Details of the waveguide assembly 210 are discussed. However, briefly here, the waveguide assembly 210 is structured to provide the non-reciprocal behavior of the circulator 200.

[0043] FIG. 2AA clockwise arrow is provided to illustrate the non-reciprocal behavior of the circulator 200. The non-reciprocal behavior of the circulator 200 includes: in response to a first signal being provided as an input signal to a first terminal 202, a second terminal 204 provides the first signal as an output signal. The non-reciprocal behavior of the circulator 200 further includes: in response to a first signal being provided as an input signal to a second terminal 204, a third terminal 206 provides the first signal as an output signal. Furthermore, the non-reciprocal behavior of the circulator 200 includes: in response to a first signal being provided as an input signal to a third terminal 206, a first terminal 202 provides the first signal as an output signal.

[0044] FIG. 2B Depicting various embodiments FIG. 2A Exploded view of waveguide assembly 210. FIG. 2B The exploded view of waveguide assembly 210 in the middle is a side view (e.g., from...). FIG. 2A Rotate the top view by 90 degrees o The waveguide assembly 210 includes an upper waveguide subassembly 220, a lower waveguide subassembly 240, and a waveguide member 226 (e.g., a stripline) disposed between the upper waveguide subassembly 220 and the lower waveguide subassembly 240. An upper shield 212 is disposed above the upper waveguide subassembly 220. A lower shield 214 is disposed below the lower waveguide subassembly 240. The upper shield 212 and the lower shield 214 may be magnetic shields.

[0045] The upper waveguide assembly 220 includes an upper magnet 222 (e.g., an upper magnetic member), an upper ferrite member 224, and an upper pole assembly 230, which is vertically disposed between the upper magnet 222 and the upper ferrite member 224. Similarly, the lower waveguide assembly 240 may include a lower magnet 242 (e.g., a lower magnetic member), a lower ferrite member 244, and a lower pole assembly 250, which is vertically disposed between the lower magnet 242 and the lower ferrite member 244. Therefore, the waveguide assembly 210 can exhibit vertical symmetry in reflections on the plane of the waveguide member 226. In some embodiments, the upper magnet 222 and the lower magnet 242 may be permanent magnets. In other embodiments, the upper magnet 222 and the lower magnet 242 may be electromagnets.

[0046] Various embodiments of the upper magnetic pole assembly 230 and the lower magnetic pole assembly 250 are constituted by one or more magnetic pole members. FIG. 2BIn the illustrated non-limiting embodiment, each of the upper magnet 222, the upper pole assembly 230, the upper ferrite member 224, the lower ferrite member 244, the lower pole assembly 250, and the lower magnet 242 can be described as a cylindrical disk. Thus, in addition to symmetry about a horizontal plane, the waveguide assembly can also include overall rotational symmetry about a vertical axis. However, as discussed below, the pole members can not include rotational symmetry due to the shape (e.g., thickness) and / or magnetic permeability of the pole members.

[0047] FIGS. 3A-6B Various embodiments of pole assemblies and pole members are illustrated. However, briefly stated here, a pole member can be a cylindrical disk (or other such shape) constructed of one or more high magnetic permeability materials. In some embodiments, the shape of one or more pole members can vary spatially (e.g., from one or more perturbations from a cylindrical disk). For example, the thickness of a pole member can vary as a function of position on the upper (or lower) surface of the cylindrical disk. Additionally and / or alternatively, the magnetic permeability of a pole member can vary as a function of position on the upper (or lower) surface of the cylindrical disk. Spatial variation of a pole member can be achieved by fabricating the pole member from multiple materials having different magnetic permeability (e.g., a composite pole member).

[0048] Spatial variation of the shape (e.g., thickness) of a pole member can be a shape / thickness gradient, and spatial variation of the magnetic permeability of a pole member can be a magnetic permeability gradient. The gradient can be a continuous gradient or a discontinuous gradient. Some gradients can include a regular pattern and / or have one or more directions of symmetry (e.g., a symmetric gradient). Other gradients can be irregular and / or asymmetric. FIGS. 3A-6B The spatial variations (or gradients) of shape / thickness and / or magnetic permeability illustrated in the figures are not intended to be limiting. One or more pole members can be fabricated to have substantially any spatial variation (or gradient) of thickness and / or magnetic permeability that is desired to increase the uniformity of a particular magnetic field.

[0049] FIGS. 3A-3F Top views of various pole members according to embodiments are illustrated. FIG. 3A A pole assembly 300 having a pole member 302 according to various embodiments is illustrated. The pole assembly 300 can be similar to the upper pole assembly 230 and / or the lower pole assembly 250 of FIG. 2A In non-limiting embodiments, the pole member 302 can be shaped as a cylindrical (circular or elliptical) cylinder having a relatively low aspect ratio (e.g., the aspect ratio of the pole member 302 can be significantly less than 1.0). The pole member 302 can be constructed of a material having a relatively high magnetic permeability. FIG. 3AThe view may be a top view (or bottom view) of the magnetic pole member 302. The magnetic pole member 302 includes a plurality of gaps (or holes), such as gap 304, through the volume of the magnetic pole member 302. The gaps (or holes) may include through-holes through the volume of the magnetic pole member 302. The gaps may be drilled holes in the upper (or lower) surface of the magnetic pole member 302. FIG. 3A The pattern of multiple gaps shown is for illustrative purposes only. The shape, size, location, and number of gaps can vary depending on the specific circumstances of shaping and / or focusing the non-uniform magnetic field. FIG. 3A The differences are shown. It should be noted that... FIG. 3A It is non-restrictive, and the size of the voids does not need to be uniform. Additionally, the pattern of the voids (e.g., holes or perforations) can be symmetrical, but does not need to be. It should be noted that the shape of the magnetic pole member 302 varies spatially because some portions have a positive (finite) thickness, while other portions (e.g., void 304) have a thickness of 0.0. Although the spatial variation in thickness... FIG. 3A While depicted as discontinuous, in other embodiments, the spatial variation can be continuous at least to some extent. For example, the sidewalls of the void may slope inward or outward to provide a thickness gradient, thus forming the void.

[0050] FIG. 3B Another magnetic pole member 312 according to various embodiments is shown. Magnetic pole member 312 may be included in... FIG. 2A In the upper magnetic pole assembly 230 and / or the lower magnetic pole assembly 250. The magnetic pole member 312 can be coupled with... FIG. 3A Similar to the magnetic pole member 302. However, instead of having multiple gaps (e.g., drilled or perforated), the magnetic pole member 312 has multiple recesses (e.g., recesses 314). The recesses can be similar to the gaps, except that they have a depth less than the finite vertical thickness of the magnetic pole member 312. The recesses can be etched portions on one or more surfaces of the magnetic pole member 312. The etched portions can be manufactured via an electrochemical etching process. FIG. 3A The discussion is similar. FIG. 3B It is non-restrictive, and the shape, size, positioning, and arrangement of the recess can be consistent with... FIG. 3B The depiction differs from that in the illustration. For example, the sidewalls of the recess may be sloped to provide a gradient in the thickness of the magnetic pole member 312. The depth of the recess may vary, as indicated by the different styles of shading shown for the recess. Furthermore, in at least some embodiments, one or more of the recesses may be "plugged" with an insert (or plug) of a material whose permeability differs from that of the material of the cylindrical disk (or other 3D shape) constituting the magnetic pole member 312.

[0051] FIG. 3C Another magnetic pole member 322 according to various embodiments is shown. Magnetic pole member 322 may be included in...FIG. 2A In the upper magnetic pole assembly 230 and / or the lower magnetic pole assembly 250. The magnetic pole member 312 can be coupled with... FIG. 3A Magnetic pole component 302 and / or FIG. 3B The magnetic pole member 312 is similar. However, instead of having a void (e.g., magnetic pole member 302) or a recess (e.g., magnetic pole member 312), the magnetic pole member 322 has a radial gradient 324, as indicated by different styles of shading, which is a function of a radial component (e.g., a polar coordinate system applied to the upper surface of the magnetic pole member 322). In some embodiments, the radial gradient 324 may be a radial gradient of the thickness of the magnetic pole member 322. In other embodiments, the radial gradient 324 may be a radial gradient of the permeability of the magnetic pole member 322. For example, the magnetic pole member 322 may be a composite magnetic pole member made of multiple materials having multiple permeabilities. In some embodiments, the radial gradient 324 is a gradient of both thickness and permeability. The gradient distribution map of the thickness gradient does not need to be the same as the gradient distribution map of the permeability gradient. Although FIG. 3C Discrete jumps of the radial gradient 324 are shown, but in other embodiments, the gradient may be continuous at least to some extent.

[0052] FIG. 3D Another magnetic pole member 332 is shown according to various embodiments. Magnetic pole member 332 can be coupled with… FIG. 3C The magnetic pole member 322 is similar. However, instead of having a radial distribution pattern, the magnetic pole member 332 may have an azimuth gradient 334 of at least one of the thickness or permeability of the magnetic pole member 332. In some embodiments, the gradient of the magnetic pole member may depend on both the radial component and the azimuth component of the polar coordinate system. FIG. 3E Another magnetic pole member 342 is shown, which has a helical gradient 344 in at least one of the thickness and / or permeability of the magnetic pole member 342. FIG. 3F Another magnetic pole member 352 is shown, which has an asymmetric gradient 354 in at least one of the thickness and / or permeability of the magnetic pole member 352.

[0053] and FIGS. 3A-3F Compared to the top views of various embodiments of the magnetic pole components, FIGS. 4A-4C Various additional embodiments of the magnetic pole member are shown in a side view rotated 90° from the top view. FIG. 4A Another magnetic pole member 402 according to various embodiments is shown. The magnetic pole member 402 includes a plurality of protrusions (e.g., protrusions 404) on its upper and lower surfaces. In other embodiments, protrusions may be included on only one of the upper or lower surfaces of the magnetic pole member 402. Although the protrusions are on... FIG. 4AThe protrusions are shown as regular shapes, but the protrusions can have irregular shapes and need not be uniformly shaped. In some embodiments, the sidewalls of the protrusions can be tilted inward or outward. In various embodiments, the protrusion portions can be made of a material equivalent (or similar) to the body of the cylindrical disk of the pole member 402, such that the permeability of the body of the cylindrical disk and the protrusions are equivalent (or at least similar). In other embodiments, the materials of the protrusions and the cylindrical disk can not be similar, such that the permeability of the protrusions and the cylindrical disk are not similar. In still other embodiments, the material (and thus the permeability) can vary across the protrusions. For example, a first protrusion (e.g., the protrusion 404) can be made of a different material than a second protrusion.

[0054] FIGS. 4B-4C Side views of various continuous thickness gradients for pole members are shown, according to embodiments. FIGS. 4B-4C The thickness gradients shown in are not intended to be limiting, and pole members can be constructed via other thickness gradients. More specifically, FIG. 4B Side views of various convex pole members are shown, according to embodiments. FIG. 4B A bi-convex pole member 412, a plano-convex pole member 422, and a convex-crescent pole member 432 are shown. FIG. 4C Side views of various concave pole members are shown, according to embodiments. FIG. 4C A bi-concave pole member 442, a plano-concave pole member 452, and a concave-crescent pole member 462 are shown.

[0055] FIG. 5A A pole assembly 500 including a plurality of pole members is shown, according to various embodiments. FIG. 5A A side-on view of the pole assembly 500 is shown. More specifically, the pole assembly 500 includes a first pole member 502 and a second pole member 504. Although the first pole member 502 and the second pole member 504 are shown as being similar to the pole member 302 of FIG. 5A FIG. 3A The pole members 302 of the pole assembly 300 are shown as being similar to the pole member 302 of the pole assembly 300, but embodiments are not so limited, and each of the first pole member 502 and the second pole member 504 can be any of the pole members envisioned herein. The first pole member 502 can include a first spatial variation of at least one of its shape or its permeability. The second pole member 504 can include a second spatial variation of at least one of its shape or its permeability. In some embodiments, the first spatial variation of the first pole member 502 can be equivalent (or at least similar) to the second spatial variation of the second pole member 504. In other embodiments, the first spatial variation of the first pole member 502 can not be similar to the second spatial variation of the second pole member 504.

[0056] As FIG. 5A ​In the exploded view shown in FIG. 5, in the pole assembly 500, the first pole member 502 and the second pole member 504 can be vertically stacked. At least one of the first pole member 502 or the second pole member 504 can be configured to rotate about a vertical rotation axis 506. By changing the relative angle between the first pole member 502 and the second pole member 504 about the rotation axis 506, the spatial variation of the magnetic reluctance of the pole assembly 500 can be changed. Thus, the spatial variation of the magnetic reluctance of the pole assembly 500 can be “tuned” by “tuning” (e.g., rotating) the relative angle between the first pole member 502 and the second pole member 504. Thus, the pole assembly 500 can be tuned according to the particular non-uniformity of the magnetic circuit within the circulator. A circulator including the pole assembly 500 can be calibrated after manufacture to achieve precise signal routing and isolation by enabling relative rotation of the first pole member 502 and the second pole member 504. In some embodiments, the calibration or tuning of a precision circulator can be performed in situ within a cryogenic chamber. The inclusion of two pole members within a single pole assembly is not limiting, and various pole assemblies can include three or more pole members. Such pole assemblies can enable relative rotation between each pair of pole members included in the pole assembly. Pole assemblies including two or more pole members, such as but not limited to the pole assembly 500, can be referred to as compound pole assemblies.

[0057] FIG. 5B Various pole assemblies providing tunable spatial variation of the magnetic reluctance of the pole assemblies are shown in accordance with various embodiments. More specifically, FIG. 5B A first pole assembly 510, a second pole assembly 520, and a third pole assembly 530 are shown. Each of the first pole assembly 510, the second pole assembly 520, and the third pole assembly 530 is a compound pole assembly. That is, each of the first pole assembly 510, the second pole assembly 520, and the third pole assembly 530 includes at least a first pole member and a second pole member. Each of the first pole member and the second pole member of a pole assembly can be similar to the pole members 302 of the pole assembly 300, as discussed in connection with FIG. 3A The pole members 302 of the pole assembly 300 can be similar in that each of the pole members can include a plurality of voids (e.g., perforations and / or drillings). Although embodiments are not limited in this regard, as discussed in connection with FIG. 5A The compound pole assemblies can be constructed via any combination of any of the pole members contemplated herein.

[0058] FIG. 5B The pole assemblies are shown in top view similar to the view of the pole members provided by FIGS. 3A-3F Thus, in the top view of FIG. 5B the second pole member in each of the pole assemblies is below (and thus mostly obscured) in FIG. 5B However, asFIG. 5A As shown, the spatial variation of the reluctance of the composite pole assembly can be tuned by the relative rotation between the two pole members. Although FIG. 5B The spatial variation of the permeability of the composite pole assembly can be tuned via similar relative rotation of the pole members, although not explicitly shown.

[0059] FIG. 6A A top view of another pole member 602 having a plurality of voids is shown. Thus, the pole member 602 can be similar to FIG. 3A the pole member 302 of FIG. 1. However, FIG. 6A The voids in the pole member 602 can be radial fins (e.g., radial cutouts) rather than drilled holes. FIG. 6B A composite pole assembly according to various embodiments is shown. More specifically, FIG. 6B A first pole assembly 610 and a second pole assembly 620 are shown. Each of the first pole assembly 610 and the second pole assembly 620 can be a composite pole assembly composed of a first pole member and a second pole member similar to FIG. 6B the pole member 602 of FIG. 2. As shown, the spatial variation of the thickness of the combination of pole members can be tuned by the relative rotation between the pole members. FIG. 6B

[0060] Additional Embodiments

[0061] Some embodiments include a waveguide assembly within a non-reciprocal electronic device. The waveguide assembly can include a ferrite member, a magnetic member, and a pole assembly, e.g., see FIG. 2A The pole assembly, in combination with at least the ferrite member and the magnetic member, forms a magnetic circuit. The pole assembly has a spatial variation of reluctance. The spatial variation of the reluctance of the pole assembly provides an increase in uniformity of magnetic flux throughout a volume of the ferrite member. Due to the increase in the uniformity of the magnetic flux, non-reciprocal properties of the electronic device are enhanced.

[0062] The electronic device can include a waveguide assembly, a first port, a second port, and a third port, e.g., see FIG. 2A The non-reciprocal properties of the electronic device can include the second port providing a first signal as an output signal in response to the first signal being provided as an input signal to the first port. The non-reciprocal properties of the electronic device can further include the third port providing the first signal as an output signal in response to the first signal being provided as an input signal to the second port. The non-reciprocal properties of the electronic device can also include the first port providing the first signal as an output signal in response to the first signal being provided as an input signal to the third port.

[0063] ​In some embodiments, the magnetic pole assembly includes a first magnetic pole member. The first magnetic pole member can have a spatial variation (e.g., discontinuous or continuous gradient) that provides a spatial variation of the reluctance of the magnetic pole assembly. The spatial variation of the first magnetic pole member can include a spatial variation of at least one of a shape (e.g., thickness) or a magnetic permeability of the first magnetic pole member.

[0064] In some non-limiting embodiments, the spatial variation of the shape of the first magnetic pole member includes a plurality of voids positioned in a volume of the first magnetic pole member (e.g., see FIG. 3A ). The plurality of voids positioned in the volume of the first magnetic pole member can include a plurality of perforations in an entire surface of the first magnetic pole member. In other embodiments, the plurality of voids positioned in the volume of the first magnetic pole member includes a plurality of recesses positioned on a surface of the first magnetic pole member, e.g., see FIG. 3B . In various embodiments, the spatial variation of the shape of the first magnetic pole member includes a plurality of etchings positioned on a surface of the first magnetic pole member. The plurality of etchings positioned on the surface of the first magnetic pole member can be generated via an electrochemical etching process.

[0065] In yet other embodiments, the spatial variation of the shape of the first magnetic pole includes a plurality of protrusions positioned on a surface of the first magnetic pole member (e.g., see FIG. 4A ). The spatial variation of the shape of the first magnetic pole member includes a gradient of a thickness of the first magnetic pole member. The gradient of the thickness of the first magnetic pole member includes a gradient along a radial direction of the first magnetic pole member. The gradient of the thickness of the first magnetic pole member can include a gradient along a radial direction of the first magnetic pole member, e.g., see FIG. 3C . The gradient of the thickness of the first magnetic pole member can additionally and / or alternatively include a gradient of the thickness along an azimuthal direction of the first magnetic pole member, e.g., see FIG. 3D . In some embodiments, the first magnetic pole member is a composite magnetic pole member composed of a plurality of materials having individual magnetic permeabilities. The variation of the magnetic permeability of the first magnetic pole member is provided by positioning each of the plurality of materials within a volume of the first magnetic pole member.

[0066] In some embodiments, the first magnetic pole member is a first cylindrical disk. The spatial variation of the first magnetic pole member is a first spatial variation. The magnetic pole assembly further includes a second magnetic pole member that is a second cylindrical disk positioned on a top of the first magnetic pole member, e.g., see FIG. 5AThe first and second pole members have a common vertical axis of rotation, and the second pole member has a second spatial variation. The first pole member can be rotated relative to the second pole member about the common vertical axis of rotation by a first angle. The combination of the first spatial variation of the first pole member and the second spatial variation of the second pole member provides an increase in uniformity of magnetic flux throughout a volume of the ferrite member, e.g., see FIG. 5B and FIG. 6B The first pole member can be rotated in place within a cryogenic chamber that houses electronic devices.

[0067] Other embodiments include a quantum computing system. The quantum computing system can include a plurality of qubits, a quantum logic circuit (QLC), and a circulator device. The QLC is enabled to perform a set of quantum operations on the plurality of qubits. The circulator device is enabled to non-reciprocally route signals associated with the set of quantum operations. The circulator device can include a ferrite member, a magnetic member, and a pole assembly. The pole assembly, in combination with at least the ferrite member and the magnetic member, forms a magnetic circuit. The pole assembly has a spatial variation of magnetic reluctance. The spatial variation of the magnetic reluctance of the pole assembly provides an increase in uniformity of magnetic flux throughout a volume of the ferrite member. As a result of the increase in the uniformity of the magnetic flux, non-reciprocal properties of the circulator device are enhanced. The quantum computing system can further include a cryogenic chamber. The plurality of qubits, the QLC, and the circulator device can be positioned within the cryogenic chamber.

[0068] Still other embodiments relate to a cryogenic system. The cryogenic system can include a cryogenic chamber and a circulator device positioned within the cryogenic chamber. The circulator device can include a ferrite member, a magnetic member, and a pole assembly. The pole assembly, in combination with at least the ferrite member and the magnetic member, forms a magnetic circuit. The pole assembly has a spatial variation of magnetic reluctance. The spatial variation of the magnetic reluctance of the pole assembly provides an increase in uniformity of magnetic flux throughout a volume of the ferrite member. As a result of the increase in the uniformity of the magnetic flux, non-reciprocal properties of the circulator device are enhanced. The quantum computing system can further include a cryogenic chamber. The plurality of qubits, the QLC, and the circulator device can be positioned within the cryogenic chamber.

[0069] The digital, classical and / or quantum themes described in this specification, as well as the implementations of digital function operations and quantum operations, can be implemented in digital electronic circuitry, suitable quantum circuitry or, more generally, quantum computing systems, in tangibly-embodied digital and / or quantum computer software or firmware, in digital and / or quantum computer hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. The term “quantum computing system” can include, without limitation, a quantum computer / computing system, a quantum information processing system, a quantum cryptography system, or a quantum simulator.

[0070] Implementations of the digital and / or quantum themes described in this specification can be implemented as one or more digital and / or quantum computer programs, i.e., one or more modules of digital and / or quantum computer program instructions encoded on a tangible non-transitory storage medium for execution by, or to control the operation of, data processing apparatus. The digital and / or quantum computer storage medium can be a machine-readable storage device, a machine-readable storage substrate, a random or serial access memory device, one or more qubits / qubit structures, or a combination of one or more of them. Alternatively or additionally, the program instructions can be encoded on an artificially generated propagated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal, that is generated to encode digital and / or quantum information for transmission to a suitable receiver device for execution by a data processing apparatus.

[0071] The terms quantum information and quantum data refer to information or data carried, held, or stored by a quantum system, where the smallest non-trivial system is a qubit, i.e., a system that defines a unit of quantum information. It should be understood that the term “qubit” encompasses all quantum systems that can be appropriately approximated as a two-level system in the corresponding context. Such quantum systems can include multi-level systems, e.g., having two or more energy levels. By way of example, such systems can include atoms, electrons, photons, ions, or superconducting qubits. In many implementations, the computational basis states are identified with a ground state and a first excited state, however, it should be understood that other arrangements in which the computational states are identified with higher-level excited states (e.g., qubits) are also possible.

[0072] The term“data processing apparatus” refers to digital and / or quantum data processing hardware and encompasses all kinds of apparatus, devices, and machines for processing digital and / or quantum data, including by way of example a programmable digital processor, a programmable quantum processor, a digital computer, a quantum computer, or multiple digital and quantum processors or computers, and combinations thereof. The apparatus can also be, or further include, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit), or a quantum simulator, i.e., a quantum data processing apparatus designed to simulate or produce quantum data about a particular quantum system. In particular, a quantum simulator is a special purpose quantum computer that does not have the ability to perform general quantum computation. The apparatus can optionally include, in addition to the hardware, code that creates an execution environment for digital and / or quantum computer programs, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them.

[0073] A digital or classical computer program, which can also be referred to or described as a program, software, software application, module, software module, script, or code, can be written in any form of programming language, including compiled or interpreted languages, or declarative or procedural languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a digital computing environment. A quantum computer program, which can also be referred to or described as a program, software, software application, module, software module, script, or code, can be written in any form of programming language, including compiled or interpreted languages, or declarative or procedural languages, and it can be translated into a suitable quantum programming language, or written in a quantum programming language such as QCL, Quipper, Cirq, etc.

[0074] A digital and / or quantum computer program can, but need not, correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code). A digital and / or quantum computer program can be deployed to be executed on one digital or one quantum computer or on multiple digital and / or quantum computers working in concert. A quantum data communication network is understood to be a network that can transmit quantum data using quantum systems (e.g., qubits). Generally, a digital data communication network cannot transmit quantum data, however, a quantum data communication network can transmit both quantum data and digital data.

[0075] The processes and logic flows described in this specification can be performed by one or more programmable digital and / or quantum computers, which can operate with one or more digital and / or quantum processors to execute one or more digital and / or quantum computer programs to perform functions by operating on input digital and quantum data and generating output. The processes and logic flows can also be performed by, or in combination with, special- purpose logic circuitry, e.g., an FPGA or an ASIC or quantum simulator, and devices can also be implemented as such special-purpose logic circuitry or a combination of the described special-purpose logic circuitry and one or more programmed digital and / or quantum computers.

[0076] For a system of one or more digital and / or quantum computers or processors “configured to” or “operable to” perform particular operations or actions means that the system has installed on it software, firmware, hardware, or a combination thereof that in operation cause the system to perform the operations or actions. For one or more digital and / or quantum computer programs to be configured to perform particular operations or actions means that the one or more programs include instructions that operate on digital and / or quantum data to cause the device or devices on which the one or more programs operate to perform the operations or actions. Quantum computers can receive instructions from digital computers that cause the device to perform operations or actions when executed by the quantum computing device.

[0077] Digital and / or quantum computers suitable for the execution of a digital and / or quantum computer program can be based on general or special purpose digital and / or quantum microprocessors or both, or any other kind of central digital and / or quantum processing unit. Generally, a central digital and / or quantum processing unit will receive instructions and digital and / or quantum data from a read only memory or from a random access memory or quantum systems suitable for transmitting quantum data (e.g., photons) or both, or combinations thereof.

[0078] Some example elements of a digital and / or quantum computer are a central processing unit for performing or executing instructions and one or more memory devices for storing instructions and digital and / or quantum data. The central processing unit and memory can be supplemented by, or incorporated in, special-purpose logic circuitry or quantum simulators. Generally, a digital and / or quantum computer will also include, or be operatively coupled to receive digital and / or quantum data from or transfer digital and / or quantum data to, or both, one or more mass storage devices for storing digital and / or quantum data, e.g., magnetic, magneto-optical disks, or optical disks, or quantum systems suitable for storing quantum information. However, a digital and / or quantum computer need not have such devices.

[0079] Digital and / or quantum computer-readable media suitable for storing digital and / or quantum computer program instructions and digital and / or quantum data include all forms of non-volatile digital and / or quantum memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks; and quantum systems, e.g., trapped atoms or electrons. It is understood that quantum memory is a device capable of storing quantum data for long periods of time with high fidelity and high efficiency, e.g., an optical-matter interface that uses light to transmit and matter to store and preserve quantum features such as superposition or quantum coherence.

[0080] The control of the various systems described in this specification, or portions thereof, can be implemented in a digital and / or quantum computer program product, including instructions stored on one or more tangible non-transitory machine-readable storage media that are executable by one or more digital and / or quantum processing devices. The systems described in this specification, or portions thereof, can each be implemented as a device, method, or electronic system that can include one or more digital and / or quantum processing devices and memory for storing executable instructions to perform the operations described in this specification.

[0081] Although this specification contains many specific implementation details, these should not be construed as limiting the scope of what can be claimed, but as descriptions of features that can be particular to particular implementations. Certain features described in this specification in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation can also be implemented separately or in any suitable subcombination. Moreover, although features can be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination and the claimed combination can be directed to a subcombination or variation of a subcombination.

[0082] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring such an order, nor that all illustrated operations be performed, to implement such operations, and nor that the illustrated operations be performed in the order shown. Rather, many tasks can be performed concurrently, and / or in a different order than depicted. Moreover, the separation of various system modules and components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated in a single software product or packaged into multiple software products.

[0083] Particular implementations of the subject matter have been described. Other implementations are within the scope of the following claims. For example, the acts recited in the claims can be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures can not require the particular order shown, or in sequential order, to achieve the desired results. In some cases, multitasking and parallel processing can be advantageous.

Claims

1. A waveguide assembly located within a non-reciprocal electronic device, the waveguide assembly comprising: a ferrite member; a magnetic member; and a pole assembly, the pole assembly in combination with at least the ferrite member and the magnetic member forming a magnetic circuit, wherein the pole assembly has a spatial variation of magnetic reluctance that provides an increase in uniformity of magnetic flux throughout a volume of the ferrite member to provide non-reciprocal behavior of the electronic device due to the increase in the uniformity of the magnetic flux.

2. The waveguide assembly of claim 1, wherein the electronic device comprises: the waveguide assembly; a first port; a second port; and a third port, wherein the non-reciprocal behavior of the electronic device comprises: in response to a first signal being provided as an input signal to the first port, the second port providing the first signal as an output signal; in response to the first signal being provided as the input signal to the second port, the third port providing the first signal as the output signal; and in response to the first signal being provided as the input signal to the third port, the first port providing the first signal as the output signal.

3. The waveguide assembly of claim 1, wherein the pole assembly comprises a first pole member, the first pole member having a spatial variation that provides the spatial variation of the magnetic reluctance of the pole assembly.

4. The waveguide of claim 3, wherein the spatial variation of the first pole member comprises a spatial variation of at least one of a shape or a permeability of the first pole member.

5. The waveguide assembly of claim 4, wherein the spatial variation of the shape of the first pole member comprises a plurality of voids located in a volume of the first pole member.

6. The waveguide assembly of claim 5, wherein the plurality of voids located in the volume of the first pole member comprises a plurality of perforations in an entire surface of the first pole member.

7. The waveguide assembly of claim 5, wherein the plurality of voids located in the volume of the first pole member comprises a plurality of recesses located on a surface of the first pole member.

8. The waveguide assembly of claim 4, wherein the spatial variation of the shape of the first pole member comprises a plurality of etchings located on a surface of the first pole member.

9. The waveguide assembly of claim 8, wherein the plurality of etchings located on the surface of the first pole member are generated via an electrochemical etching process.

10. The waveguide assembly of claim 4, wherein the spatial variation of the shape of the first pole comprises a plurality of protrusions located on a surface of the first pole member.

11. The waveguide assembly of claim 4, wherein the spatial variation of the shape of the first pole member comprises a gradient of a thickness of the first pole member.

12. The waveguide assembly of claim 11, wherein the gradient of the thickness of the first pole member comprises a gradient along a radial direction of the first pole member. ​ ​ 13. The waveguide assembly of claim 11, wherein the gradient of the thickness of the first pole member comprises a gradient of thickness along an azimuthal direction of the first pole member.

14. The waveguide assembly of claim 4, wherein the first pole member is a composite pole member composed of a plurality of materials having individual magnetic permeabilities, such that the variation of the magnetic permeability of the first pole member is provided by positioning each of the plurality of materials within a volume of the first pole member.

15. The waveguide assembly of claim 4, wherein the first pole member is a first cylindrical disk, the spatial variation of the first pole member is a first spatial variation, and the pole assembly further comprises: a second pole member that is a second cylindrical disk positioned on top of the first pole member such that the first pole member and the second pole member have a common vertical axis of rotation and the second pole member has a second spatial variation.

16. The waveguide assembly of claim 15, wherein the first pole member is rotated relative to the second pole member about the common vertical axis of rotation by a first angle, such that the combination of the first spatial variation of the first pole member and the second spatial variation of the second pole member provides the increase in the uniformity of the magnetic flux throughout the volume of the ferrite member.

17. The waveguide assembly of claim 16, wherein the first pole member is rotated in place in a cryogenic chamber that houses the electronic device.

18. A quantum computing system, comprising: a plurality of qubits; a quantum logic circuit (QLC) that enables the QLC to perform a set of quantum operations on the plurality of qubits; and a circulator device that enables the circulator device to non-reciprocally route signals associated with the set of quantum operations, wherein the circulator device comprises: a ferrite member; a magnetic member; and a pole assembly that, in combination with at least the ferrite member and the magnetic member, forms a magnetic circuit, wherein the pole assembly has a spatial variation of magnetic reluctance that provides an increase in the uniformity of a magnetic flux throughout a volume of the ferrite member to provide non-reciprocal behavior of the circulator device due to the increase in the uniformity of the magnetic flux.

19. The quantum computing system of claim 18, further comprising a cryogenic chamber, wherein the plurality of qubits, the QLC, and the circulator device are positioned within the cryogenic chamber.

20. A cryogenic system, comprising: a cryogenic chamber; and a circulator device positioned within the cryogenic chamber, the circulator device comprising: a ferrite member; a magnetic member; and a pole assembly that, in combination with at least the ferrite member and the magnetic member, forms a magnetic circuit, wherein the pole assembly has a spatial variation of magnetic reluctance that provides an increase in the uniformity of a magnetic flux throughout a volume of the ferrite member to provide non-reciprocal behavior of the circulator device due to the increase in the uniformity of the magnetic flux. A magnetic pole assembly in combination with at least the ferrite member and the magnetic member forms a magnetic circuit, wherein the magnetic pole assembly has a spatial variation of reluctance that provides an increase in uniformity of magnetic flux throughout a volume of the ferrite member to provide a non-reciprocal behavior of the circulator device due to the increase in the uniformity of the magnetic flux.

Images