Filter for laminated circuit assembly

Abstract

A laminated circuit assembly for filtering signals in one or more signal lines in, for example, a quantum computing system is provided. In one example, the laminated circuit assembly includes one or more signal lines disposed within a substrate in a first direction. The laminated circuit assembly includes a dielectric portion of the substrate. The laminated circuit assembly includes a filter portion of the substrate, the filter portion extending in the first direction and containing a frequency absorbing material that provides less attenuation for a first signal at a first frequency than for a second signal at a higher second frequency. The filter portion is configured to attenuate an infrared signal passing through the one or more signal lines.

Description

[0001] CLAIM OF PRIORITY

[0002] This application claims the benefit of priority to U.S. Provisional Application entitled “Filter for Laminated Circuit Assembly,” Serial No. 63 / 079,258, filed September 16, 2020, which is incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates generally to laminated circuit assemblies. More particularly, aspects of the present disclosure relate to filters for laminated circuit assemblies. BACKGROUND

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

[0006] One example aspect of the present disclosure is directed to a laminated circuit assembly. The laminated circuit assembly includes one or more signal lines disposed within a substrate in a first direction. The laminated circuit assembly includes a dielectric portion of the substrate. The laminated circuit assembly includes a filter portion of the substrate, the filter portion extending in the first direction and containing a frequency absorbing material that provides less attenuation of a first signal at a first frequency than a second signal at a higher second frequency. The filter portion is configured to attenuate an infrared signal passing through the one or more signal lines.

[0007] Another example aspect of the present disclosure is directed to a method for manufacturing a filter for a signal line. The method includes receiving a laminated circuit assembly having one or more signal lines disposed in a first direction within a dielectric material of a substrate, where a second direction is perpendicular to the substrate and a third direction is orthogonal to the first direction and the second direction. The method includes forming a cavity within the substrate by removing a portion of the dielectric material above the signal line in the second direction, the cavity extending in the first direction along the signal line. The method includes filling the cavity with a frequency absorbing material. The frequency absorbing material provides less attenuation to a first signal at a first frequency than to a second signal at a second, higher frequency. The filled cavity is configured to attenuate an infrared signal passing through the one or more signal lines.

[0008] Other aspects of the present disclosure are directed to various systems, methods, apparatus, non-transitory computer-readable media, computer-readable instructions, and computing devices.

[0009] These and other features, aspects, and advantages of various embodiments of the present disclosure will be better understood when read with reference to the following description and appended claims in conjunction with the accompanying drawings. The accompanying drawings illustrate example embodiments of the present disclosure and, together with the description, serve to explain the related principles. BRIEF DESCRIPTION OF DRAWINGS

[0010] A detailed discussion of embodiments in the context of a specific application is presented herein for purposes of enabling the reader to make and use the application. For the purpose of explanation, specific nomenclature is used to describe the embodiments. However, specific embodiments disclosed herein are meant to be illustrative only and not limiting. One skilled in the art will recognize many variations that will fall within the scope and spirit of the present disclosure. For example, the present disclosure is applicable to any suitable quantum computing system.

[0011] Figure 1 An example quantum computing system is depicted in accordance with example embodiments of the present disclosure;

[0012] Figure 2 An example quantum computing system is depicted in accordance with example embodiments of the present disclosure;

[0013] Figure 3 An isometric cross-sectional view of an example portion of a laminated circuit assembly is depicted in accordance with example embodiments of the present disclosure;

[0014] Figure 4 An isometric cross-sectional view of an example portion of a processed laminated circuit assembly is depicted in accordance with example embodiments of the present disclosure;

[0015] Figure 5 An isometric cross-sectional view of an example portion of a processed laminated circuit assembly is depicted in accordance with example embodiments of the present disclosure;

[0016] Figure 6 An isometric cross-sectional view of an example portion of a processed laminated circuit assembly is depicted in accordance with example embodiments of the present disclosure;

[0017] Figure 7A cross-sectional view depicting an example of a processed laminated circuit assembly according to an example embodiment of the present disclosure;

[0018] Figure 8 A cross-sectional view depicting an example of a processed laminated circuit assembly according to another example embodiment of the present disclosure;

[0019] Figure 9 A cross-sectional view depicting an example of a processed laminated circuit assembly according to another example embodiment of the present disclosure;

[0020] Figure 10 A cross-sectional view depicting an example of a processed laminated circuit assembly according to another example embodiment of the present disclosure; and

[0021] Figure 11 An example method of manufacturing a laminated circuit assembly according to an example embodiment of the present disclosure. DETAILED DESCRIPTION

[0022] Example aspects of the present disclosure are directed to a laminated circuit assembly. The circuit assembly can include a signal line disposed along a substrate. The substrate can include a filter portion that provides attenuation to a signal propagating along the signal line. In some embodiments, the filter portion can provide different levels of attenuation based on a frequency of the signal on the signal line. For example, the filter portion can include an absorbing material configured to provide less attenuation to a first frequency of the signal than a second signal of a higher second frequency. In one embodiment, the filter portion can attenuate signals in an infrared frequency range.

[0023] More particularly, embodiments of the laminated circuit assembly according to example aspects of the present disclosure can include a signal line of any suitable conductive material(s) (e.g., copper, etc.). In some embodiments, the signal line can include a superconducting material, such as a material characterized by superconducting properties at approximately 10 Kelvin or below, including example temperatures below approximately 1 Kelvin and / or approximately 20 milli-Kelvin. For example, in one embodiment, the signal line can include niobium. In some embodiments, the signal line can include another superconducting material or materials in addition to a conductive material such as copper or tin. For example, the superconducting material can be coated, covered, and / or otherwise layered with another conductive material (e.g., deposited and / or electroplated copper, etc.) to protect the superconducting material, strengthen and / or harden portions of the superconducting material, and / or otherwise cooperate to form the signal line.

[0024] Embodiments of substrates according to example aspects of the present disclosure can include a dielectric material. For example, the dielectric material can include one or more polymers, one or more ceramics, or a composite thereof (e.g., a polymeric matrix with one or more ceramic fillers). In some embodiments, the dielectric material can be rigid or substantially rigid. In some embodiments, the dielectric material can include an elastic material (e.g., a flexible material). For example, one embodiment of a laminated circuit assembly includes a flexible circuit board.

[0025] As used herein, a "flexible circuit board" refers to a board that includes at least one substantially planar substrate (e.g., a layered substrate) or other support, on which one or more signal lines are formed or otherwise disposed, and which has flexibility in at least one plane. As used herein, "flexibility" refers to the ability to deform (e.g., be subjected to mechanical stress, etc.) without breaking. For example, a rectangular flexible circuit board can be flexible along its largest surface. The rectangular flexible circuit board can be flexible and / or rigid along at least a portion of its edges. Flexibility can be achieved as a property of the material(s) from which the flexible circuit board and / or layers of the flexible circuit board are formed (e.g., metals such as copper, copper alloys, niobium, aluminum, etc., dielectric materials, non-metals, polymers, rubbers, etc.), by articulating and / or segmenting the flexible circuit board (e.g., articulating and / or segmenting rigid portions), and / or in any other suitable manner. The substrate(s) can be strictly planar (e.g., have a substantially linear cross-section in length and width) and / or can be substantially planar in that the substrate(s) are curved, wrinkled, or otherwise non-linear in at least one cross-section, but generally represent a shape in which the depth is significantly less than the length and width (e.g., less than about 10% of the length and width).

[0026] In some embodiments, one or more layers of dielectric material can be laminated together to sandwich one or more signal lines therebetween, thereby forming a substrate in which the signal line(s) are embedded. However, in general, it is contemplated that the signal line(s) can be disposed along one or more surfaces of the substrate (e.g., an outer surface, such as in a microstrip implementation) and / or within the substrate according to any suitable method of construction.

[0027] Embodiments of substrates according to example aspects of the present disclosure can include a filter material. In some embodiments, the filter material can be distributed and / or embedded within the dielectric material. For example, a polymeric dielectric material can be doped with a filter material (e.g., magnetically loaded with frequency-absorbing particles). In this manner, the dielectric portion of the substrate and the filter portion of the substrate coincide, as the dielectric portion can be the portion that provides the filtering effect.

[0028] However, in some embodiments, the filter portion can comprise a different material than some other portion of the substrate, such as a dielectric portion. For example, the filter portion of the substrate can comprise a portion of dielectric material (e.g., optionally the same dielectric material) that includes a higher concentration of a frequency-absorbing component (e.g., frequency-absorbing particles) than another portion of the same or different dielectric material (e.g., which can not contain any frequency-absorbing component). It is contemplated, for example, that additive manufacturing techniques can be applied to selectively position material comprising an absorbing component within a larger portion of material that does not otherwise comprise an absorbing component.

[0029] In some examples, the filter material can provide less attenuation of a signal of a first frequency, and more attenuation of a signal of a second, higher frequency. For example, some filter materials provide attenuation that increases in a substantially monotonic manner with increasing signal frequency, for at least a portion of a target frequency band. In some embodiments, aspects of the filter material can be configured for low-pass operation and / or band-pass operation.

[0030] In some embodiments, the filter portion of the substrate can be bounded by one or more boundaries of a cavity within the substrate (e.g., a cavity within a dielectric material). For example, a cavity within the substrate can be filled with filter material (e.g., a magnetically loaded polymer). In some embodiments, the cavity can be (e.g., partially or completely) filled with filter material via an access within the substrate, when the filter material is in any pourable, injectable, and / or moldable state (e.g., flowing particles, soft / plasticized material, gel, slurry, paste, foam, un-cured thermoset material, softened / melted thermoplastic material, etc.). In some embodiments, the cavity can be filled with filter material that is substantially solid (e.g., by press-fitting into the cavity, etc.).

[0031] In some embodiments, the cavity can radially surround or otherwise enclose at least a portion of the signal line. For example, the signal line can extend in a first direction in the substrate. A second direction can be defined in a direction normal to an outer surface of the substrate (e.g., in a thickness direction of the substrate). A third direction can be defined as orthogonal to the first and second directions. Generally, the dimensions of the cavity in the first, second, and third directions can be configured to provide a desired filtering of a signal on the signal line when the cavity is filled with the filter material. For example, in one embodiment, the length of the cavity in the first direction can be extended to increase the attenuation of the filter for a given signal frequency. For example, in one embodiment, the filter material can provide a linearly increasing attenuation with a slope of at least about 0.5 dB / GHz. In addition to the length extending in the first direction, the cavity can also extend above the signal line in the second direction and / or alongside the signal line in the third direction.

[0032] In some embodiments, one or more conductors can be laminated to the substrate. For example, a planar conductor can be laminated to one surface of the substrate, and in some embodiments, another planar conductor can be laminated to the opposite surface of the substrate. For example, the substrate, signal line, and one or more planar conductors can be arranged in a microstrip or stripline configuration. In some embodiments, a conductor can be applied over one or more inlets to the cavity for filling with the filter material in the substrate. For example, a planar conductor can be laminated over the inlet(s), optionally overlapping one or more other planar conductors. In some embodiments, a conductive material can be sprayed, spread, deposited, and / or otherwise applied over the inlet(s). For example, the conductive material(s) can include a curable non-metallic matrix applied in an uncured state.

[0033] Example aspects of the present disclosure are also directed to methods of manufacturing a laminated circuit assembly. For example, a laminated circuit assembly including one or more signal lines disposed in a dielectric material of a substrate in a first direction can be received or otherwise selected for processing. In one embodiment, a cavity can be formed within the substrate. For example, the cavity can be formed by removing a portion of the dielectric material within the substrate. The material can be removed in any suitable manner, including ablation, abrasion, cutting, etc. Once formed, the cavity can be filled with a frequency absorbing material. In some embodiments, the cavity can be filled with the frequency absorbing material while the dielectric material (e.g., polymer) is in an uncured state.

[0034] For example, the frequency absorbing material can provide less attenuation for a first signal at a first frequency than for a second signal at a higher second frequency (e.g., as described herein). In some embodiments, the filled cavity can be configured to attenuate an infrared signal passing through the one or more signal lines.

[0035] In some embodiments, a first signal line can have a first filter portion corresponding thereto; and a second adjacent signal line can have a second filter portion corresponding thereto. The first filter portion and the second filter portion are offset from one another in a first direction.

[0036] Example aspects of the present disclosure are also directed to cryostats including the circuit assemblies described herein. For example, a cryostat can include one or more cooling stages for cooling one or more components of a computing system. In one embodiment, a cooling stage can be configured to cool a portion of a computing system to approximately 20 milliKelvin or less. One or more signal lines coupling a control unit to the cooled portion of the computing system can be a portion of the circuit assemblies disclosed herein including the filter portions disclosed herein.

[0037] Aspects of the present disclosure provide a number of technical effects and benefits. For example, the circuit assemblies, systems, and methods according to aspects of the present disclosure provide improved sensitive signal communication. For example, in some embodiments, a plurality of signals (e.g., control and / or other interface signals) are transmitted over signal lines of a circuit assembly according to the present disclosure. For example, a first signal can have a first frequency less than approximately 500 MHz, while a second signal can have a second frequency greater than approximately 2 GHz and less than approximately 8 GHz. The circuit assemblies according to example embodiments of the present disclosure can be configured to contain a frequency-absorbing material that provides greater attenuation to the second signal than to the first signal. In this way, the attenuation applied to each set of interface signals can be configured for desired operational characteristics. More advantageously, the circuit assemblies according to example embodiments of the present disclosure can be configured to provide greater attenuation to an infrared signal than to the first signal or the second signal. For example, in some embodiments, an infrared signal can disrupt communication and / or increase thermal load on connected components.

[0038] More advantageously, the circuit assemblies, systems, and methods according to aspects of the present disclosure provide improved manufacturability. For example, embodiments of the present disclosure can provide high performance circuit assemblies that can be manufactured at low cost and high yield.

[0039] More advantageously, the circuit assemblies, systems, and methods according to aspects of the present disclosure provide compact and scalable implementations of filtered signal lines. For example, some implementations are sensitive to signal interference (e.g., qubit interface signals), and existing methods of filtering and isolating signal lines for qubit interfaces have not provided suitably compact configurations for scaling the number of qubits in a quantum computing system.

[0040] Referring again to the drawings, additional example embodiments of the systems and methods of the present disclosure will be discussed in greater detail. The term "about," used in conjunction with a numerical value, means within 10% of the stated number.

[0041] Figure 1 An example quantum computing system 50 is depicted. The example system 50 is an example of a system implemented as a classical or quantum computer program on one or more classical computers or quantum computing devices in one or more locations in which the systems, components, and techniques described below can be implemented. Figure 1 An example quantum computing system that can be used to implement aspects of the present disclosure is depicted. Using the disclosure provided herein, one of ordinary skill in the art will understand that other quantum computing structures or systems can be used without departing from the scope of the present disclosure.

[0042] The system 50 includes quantum hardware 52 in data communication with one or more classical processors 54. For example, the quantum hardware 52 can use qubits to represent and / or manipulate information. A qubit can be or include any suitable quantum device capable of superimposing multiple states (e.g., data that is both in a "0" state and a "1" state). As one example, a qubit can be or include a unit of superconducting material, such as a superconducting material that achieves superconductivity at temperatures below approximately 10 mK.

[0043] The quantum hardware 52 can include components for performing quantum computations. For example, the quantum hardware 52 can include a quantum system 60, control device(s) 62, and readout device(s) 64 (e.g., readout resonator(s)). The quantum system 60 can include one or more multi-level quantum subsystems, such as a register of qubits. In some implementations, the multi-level quantum subsystems can include superconducting qubits, such as flux qubits, charge qubits, transmon qubits, gmon qubits, and the like.

[0044] The classical processor(s) 54 can be binary processors, such as processors that operate on data represented as a plurality of bits. As one example, a bit can be represented by a voltage difference between a low voltage (e.g., 0 V) and a high voltage (e.g., 5 V) at a reference point, such as a memory cell, a circuit node, etc. The low voltage can be associated with a “0” state, and the high voltage can be associated with a “1” state. In addition to any other suitable function(s) of the classical processor(s) 54, the classical processor(s) 54 can be configured to control the quantum hardware 52. For example, the classical processor(s) 54 can be coupled (e.g., by signal lines) to the quantum hardware 52 and / or configured to send control signals to perform quantum operations using the quantum hardware 52. As one example, the classical processor(s) 54 can be configured to send control signals that cause the quantum hardware 52 to perform a quantum gate operation (e.g., by the control device(s) 62). Additionally and / or alternatively, the classical processor(s) 54 can be configured to send control signals that cause the quantum hardware 52 to perform a quantum state measurement and / or provide the quantum state measurement to the classical processor(s) 54 (e.g., by the readout device(s) 64). For example, the classical processor(s) 54 can receive a measurement of the quantum system 60 that can be interpreted by the classical processor(s) 54.

[0045] The type of multi-level quantum subsystem utilized by the system 50 can vary. For example, in some cases, it can be convenient to include one or more readout devices 64 attached to one or more superconducting qubits (e.g., transmon, flux, gmon, xmon, or other qubits).

[0046] Quantum circuits can be constructed and applied to a register of qubits included in the quantum system 60 via a plurality of signal lines coupled to one or more control devices 62. Example control devices 62 operating on a register of qubits can be used to implement quantum logic gates or circuits of quantum logic gates (e.g., Hadamard gates, controlled-NOT (CNOT) gates, controlled-phase gates, T gates, multi-qubit quantum gates, coupler quantum gates, etc.). The one or more control devices 62 can be configured to operate on the quantum system 60 by one or more respective control parameters (e.g., one or more physical control parameters). For example, in some implementations, the multi-level quantum subsystem can be a superconducting qubit, and the control device 62 can be configured to provide a control pulse to a control line (e.g., signal line 120) to generate a magnetic field to adjust a frequency of the qubit.

[0047] The quantum hardware 52 can also include a readout device 64 (e.g., a readout resonator). Measurement results 58 obtained via the measurement device can be provided to the classical processor 54 for processing and analysis. In some implementations, the quantum hardware 52 can include a quantum circuit and control device(s) 62, and the readout device(s) 64 can implement one or more quantum logic gates that operate on the quantum system 60 by physical control parameters (e.g., microwave pulses) sent via wires included in the quantum hardware 52. Other examples of control devices include arbitrary waveform generators, where a DAC produces the signal.

[0048] The readout device(s) 64 can be configured to perform quantum measurements on the quantum system 60 and send measurement results 58 to the classical processor 54 (e.g., over signal line 120). In addition, the quantum hardware 52 can be configured to receive data from the classical processor 54 (e.g., over signal line 120) that specifies values of physical control parameters 56. The quantum hardware 52 can use the received values of physical control parameters 56 to update the actions of the control device(s) 62 and the readout device(s) 64 on the quantum system 60. For example, the quantum hardware 52 can receive data that specifies new values representing the strength of the voltage of one or more DACs included in the control device 62, and can update the actions of the DACs on the quantum system 60 accordingly. The classical processor 54 can be configured to initialize the quantum system 60 in an initial quantum state (e.g., by sending data to the quantum hardware 52 that specifies an initial set of parameters 56).

[0049] The readout device(s) 64 can measure the state of an element (e.g., a qubit) of the quantum system using an impedance difference of the element (e.g., a qubit) in the state and For example, due to the nonlinearity of a qubit, the resonant frequency of a readout resonator can take different values when the qubit is in the state or the state Thus, microwave pulses reflected from the readout device 64 carry an amplitude and a phase shift that depend on the state of the qubit. In some implementations, a Purcell filter can be used in conjunction with the readout device(s) 64 to block microwave propagation at the qubit frequency.

[0050] The system 50 includes control device(s) 62. The control device(s) 62 can operate the quantum hardware 52. For example, in accordance with example aspects of the disclosure, the control device(s) 62 can include a waveform generator configured to generate control pulses.

[0051] In some implementations, the control device(s) 62 can include a data processing apparatus and associated memory. The memory can include a computer program having instructions which, when executed by the data processing apparatus, cause the data processing apparatus to perform one or more of the functions described herein.

[0052] Figure 2 An example quantum computing system 300 is depicted in accordance with example embodiments of the present disclosure. The quantum computing system 300 can include one or more classical processors 302 and quantum hardware 304 containing one or more qubits. The quantum computing system 300 can include a chamber mount 308 configured to support the quantum hardware 304 and a vacuum chamber configured to receive the chamber mount 308 and place the quantum hardware 304 in a vacuum. The vacuum chamber can form a cooling gradient from an end of the vacuum chamber (e.g., a lid 307) to the quantum hardware 304. For example, the vacuum chamber can form a cooling gradient from a first temperature, such as room temperature (e.g., approximately 300 Kelvin), to a second temperature, such as absolute zero or approximately absolute zero (e.g., less than approximately 1 Kelvin), to provide a temperature at which qubits experience superconductivity, such as at the quantum hardware 304. In some embodiments, the cooling gradient can be formed by multiple cooling stages having progressively increasing and / or decreasing temperatures. As one example, the cooling stages can be stages of a staged cryogenic cooling system, such as a dilution refrigerator.

[0053] The quantum computing system 300 can include one or more signal lines between the classical processor(s) 302 and the quantum hardware 304. In accordance with example aspects of the present disclosure, the quantum computing system 300 can include one or more flexible circuit boards 306 that include the one or more signal lines. The flexible circuit board(s) 306 can be configured to transmit signals through the vacuum chamber over the one or more signal lines to couple the one or more classical processors 302 to the quantum hardware 304. The flexible circuit board(s) 306 can include multiple signal lines and, in addition to providing improved isolation, reduced thermal conductivity, and / or improved scalability, can provide a significantly improved signal line density. For example, inclusion of the flexible circuit board 306 in accordance with example aspects of the present disclosure to couple the classical processor 302 to the quantum hardware 304 can provide infrastructure that reliably scales to an increasing number of qubits implemented and / or anticipated in contemporary and / or future quantum computing systems.

[0054] In some embodiments, some or all of the flexible circuit boards 306 can include at least one ground layer. The ground layer can form an outer surface of the flexible circuit board 306, such as along a largest surface. In some embodiments, the flexible circuit board 306 can include two ground layers, such as two parallel and spaced apart ground layers. For example, the two ground layers can form two largest outer surfaces of the flexible circuit board 306. The ground layer can act as an electrical isolation layer to isolate signal lines on one side of the ground layer from interfering signals on the other side of the ground layer (e.g., from other layers, other boards, the environment, etc.). For example, the ground layer can be coupled to ground and / or other suitable ground or reference.

[0055] The ground layer(s) can be or can include any suitable electrically conductive material. In some embodiments, the ground layer(s) can be or can include superconducting ground layer(s) including superconducting material(s), such as superconducting material(s) that achieve superconductivity at temperatures below about 3 Kelvin, such as below about 1 Kelvin, such as below about 20 milli-Kelvin. As an example, the ground layer(s) can be or can include niobium, tin, aluminum, molybdenum disulfide, BSCCO, and / or other suitable superconducting material. Additionally and / or alternatively, the ground layer(s) can be or can include a material having high signal transfer performance characteristics (such as low resistance, low reflectivity, low distortion, etc.) such that a signal passing through the signal line is substantially unaltered. As an example, the ground layer(s) can be or can include copper, gold, and / or other suitable material having high signal transfer performance characteristics. Additionally and / or alternatively, the ground layer(s) can be or can include material(s) having desirable thermal characteristics (such as suitable high and / or low thermal transfer), such as copper, copper alloys, thin superconducting materials, etc.

[0056] In some embodiments, the respective flexible circuit board(s) 306 can include at least one dielectric layer. The dielectric layer(s) can be or can include any suitable dielectric material, such as a dielectric polymer. In some embodiments, the dielectric layer(s) can be or can include a flexible dielectric material. As one example, the dielectric layer(s) can be or can include polyimide. At least a portion of the dielectric layer(s) can be formed on or otherwise disposed proximate to at least a portion of an inner surface of the ground layer(s). For example, in some embodiments, an inner surface of the ground layer can be mated with an outer surface of the dielectric layer. Further, in some embodiments, inner surfaces of two dielectric layers can be mated with a signal line disposed therebetween.

[0057] The flexible circuit board 306 can include one or more signal lines. The one or more signal lines can be disposed on a surface (e.g., an interior surface) of at least one dielectric layer. As an example, in some implementations, the one or more signal lines can be disposed between opposing interior surfaces of two dielectric layers. The signal line(s) can be or can include any suitable conductive material. In some embodiments, the signal line(s) can be or can include superconducting signal line(s) including superconducting material(s) such as superconducting material(s) that achieve superconductivity at temperatures below about 3 Kelvin (such as below about 1 Kelvin, such as below about 20 milli-Kelvin). As an example, the signal line(s) can be or can include niobium, tin, aluminum, molybdenum disulfide, BSCCO, and / or other suitable superconducting materials. Additionally and / or alternatively, the signal line(s) can be or can include materials with high signal transfer performance characteristics. As an example, the signal line(s) can be or can include copper, gold, and / or other suitable materials with high signal transfer performance characteristics. Additionally and / or alternatively, the signal line(s) can be or can include material(s) with desirable thermal characteristics such as copper, copper alloys, thin superconducting materials, and / or the like.

[0058] In some embodiments, the flexible circuit board 306 can include one or more vias. For example, the vias can extend through the ground layer(s), the dielectric layer(s), and / or the signal line(s). The vias can be used to improve isolation of the signal lines. Additionally and / or alternatively, the vias can be used to couple multiple ground layers and / or to transfer signals between layers of the flexible circuit board. In some embodiments, the via(s) can be plated with via plate(s) that extend along the via(s). In some embodiments, the via plate(s) can be or can include conductive materials such as copper.

[0059] For example, in some embodiments, the quantum computing system 300 can include quantum hardware 304 in data communication with one or more classical processors 302. For example, the quantum hardware 304 can use qubits to represent and / or manipulate information. A qubit can be or include any suitable quantum device capable of superimposing multiple states (e.g., both a “0” state and a “1” state). As one example, a qubit can be or include a superconducting material unit such as a superconducting material that achieves superconductivity at temperatures below about 3 Kelvin (such as below about 1 Kelvin, such as below about 20 milli-Kelvin). In some embodiments, the quantum computing system 300 can include one or more multi-level quantum subsystems such as qubit registers. In some implementations, the multi-level quantum subsystems can include superconducting qubits such as flux qubits, charge qubits, transmon qubits, gmon qubits, and / or the like.

[0060] The classical processor(s) 302 can be binary processors, such as processors that operate on data represented as a plurality of bits. As one example, a bit can be represented by a voltage difference between a low voltage (e.g., 0 V) and a high voltage (e.g., 5 V) at a reference point, such as a memory cell, a circuit node, etc. The low voltage can be associated with a “0” state, and the high voltage can be associated with a “1” state. In addition to any other suitable function(s) of the classical processor(s) 302, the classical processor(s) 302 can be configured to control the quantum hardware 304. For example, the classical processor(s) 302 can be coupled to the quantum hardware 304 (e.g., according to example aspects of the present disclosure, by signal lines included in the flexible circuit board 306) and / or configured to send control signals to perform quantum operations using the quantum hardware 304. As one example, the classical processor(s) 302 can be configured to send control signals that cause implementation of a quantum gate operation at the quantum hardware 304 (e.g., by control device(s)). Additionally and / or alternatively, the classical processor(s) 302 can be configured to send control signals that cause the quantum hardware 304 to perform a quantum state measurement and / or provide the quantum state measurement to the classical processor(s) 302 (e.g., by readout device(s)). For example, the classical processor(s) 302 can receive a measurement of a quantum system that can be interpreted by the classical processor(s) 302.

[0061] According to example aspects of the present disclosure, the quantum computing system 300 can include one or more flexible circuit boards 306 that include one or more signal lines. The classical processor(s) 302 can be coupled to at least one first flexible circuit board. For example, the classical processor(s) 302 can be coupled to the first flexible circuit board(s) 314 by a classical flexible interconnect 332. The classical flexible interconnect 332 can convert from a classical signal transmission medium (e.g., a coaxial cable) 312 to the first flexible circuit board(s) 314.

[0062] As one example, the classical flexible interconnect 332 can be or can include a compression interposer. The compression interposer can include an array (e.g., a two-dimensional array) of spring pads. Connectors that receive signals from the classical processor(s) 302 (such as via one or more coaxial cables 312 (e.g., one coaxial cable 312 per signal line)) can be pressed against the compression interposer to form signal communication between the spring pads and the connectors (e.g., coaxial cables). The spring pads can each be coupled to a signal line on the first flexible circuit board 314 so that signals can be transmitted from the classical processor(s) 302 (e.g., coaxial cables) to the signal lines. The compression interposer can provide for connecting signal transmission media 312 having a relatively lower spatial density (such as coaxial cables, which can each occupy a relatively large amount of space) to signal transmission media having a relatively higher spatial density (such as the signal lines embedded in the first flexible circuit board 314 provided in accordance with example aspects of the present disclosure). Additionally, the compression interposer can enable high isolation between signal lines and / or low reflectivity along the signal lines suitable for quantum computing applications.

[0063] In some embodiments, the first flexible circuit board(s) 314 can be or can include a first flexible circuit board material at the ground layer(s) and / or signal line(s). The first flexible circuit board material can be selected to provide high signal transfer performance characteristics. As an example, the first flexible circuit board material can be or can include copper, brass, gold, and / or other suitable materials having high signal transfer performance characteristics. For example, the first flexible circuit board(s) 314 can include copper signal lines and / or ground layer(s) to provide high signal transfer performance characteristics.

[0064] The first flexible circuit board(s) 314 can pass through a hermetic seal 352, such as a lid 307, located at one end (e.g., the inlet) of the vacuum chamber. For example, a flexible circuit board (e.g., the first flexible circuit board 314) can be configured to pass through the hermetic seal 352 such that a first portion of the flexible circuit board (e.g., the first flexible circuit board 314) is disposed in the vacuum chamber and a second portion of the flexible circuit board (e.g., the first flexible circuit board 314) is disposed outside of the vacuum chamber while the hermetic seal 352 forms a vacuum seal of the vacuum chamber. The hermetic seal 352 can provide for the first flexible circuit board(s) 314 to enter the vacuum chamber without (e.g., substantially) disrupting the vacuum created by the vacuum chamber. As one example, the hermetic seal 352 can include a fitted seal for each first flexible circuit board 314. The fitted seal(s) can receive the first flexible circuit board(s) 314 and form a vacuum seal with the surface(s) of the first flexible circuit board(s) 314. Additionally, the hermetic seal 352 can include one or more seal grooves configured to receive the fitted seal(s) and / or the first flexible circuit board(s) 314. For example, the fitted seal(s) can form a vacuum seal with the seal groove(s) while allowing the first flexible circuit board(s) 314 to pass through the seal groove(s) and into the vacuum chamber. In this way, the flexible circuit board(s) 306 can enter the vacuum chamber without experiencing a signal disruption due to the circuit board breaking as the board can be continuously threaded into the vacuum chamber. In some embodiments, the hermetic seal 352 can include a fastening system, such as screws, bolts, sealing rings, O-rings, etc., to secure the fitted seal to the seal groove and / or form the vacuum seal. In some embodiments, the hermetic seal 352 can form a vacuum seal without the need for adhesive materials (e.g., glue, resin, etc.) such that, for example, residual adhesive materials do not contaminate the flexible circuit board 306.

[0065] The first flexible circuit board(s) 314 can be coupled to at least one second flexible circuit board 316. The first flexible circuit board(s) 314 can be coupled to the second flexible circuit board(s) 316 by at least one flexible-to-flexible interconnect 334. For example, the flexible-to-flexible interconnect(s) 334 can structurally and / or electrically couple the ground layer(s), dielectric layer(s), and / or signal line(s) of the first flexible circuit board 314 to the second flexible circuit board 316. As an example, the flexible-to-flexible interconnect(s) 334 can be formed by soldering, brazing, and / or otherwise fusing components of the first flexible circuit board 314 to the second flexible circuit board 316. The flexible-to-flexible interconnect(s) 334 can be or can include any suitable interconnect of two flexible circuit boards 306, such as a butt joint, a lap joint, and / or any other suitable interconnect(s).

[0066] The second flexible circuit board(s) 316 can have at least a different material composition than the first flexible circuit board(s) 314. In some embodiments, the second flexible circuit board(s) 316 can be or can include a second flexible circuit board material at the ground layer(s) and / or signal line(s). The second flexible circuit board material can be selected to provide high signal transfer performance characteristics and / or reduced thermal conductivity. As an example, the second flexible circuit board material can be or can include a copper alloy and / or other suitable material having desired thermal characteristics. For example, the second flexible circuit board(s) 316 can include copper alloy signal lines and / or ground layer(s) to provide reduced thermal conductivity from the vacuum chamber upper portion (e.g., the first circuit board 314) and / or to dissipate heat generated at subsequent components, such as the surface mount attenuator 354.

[0067] In some embodiments, the second flexible circuit board(s) 316 can be coupled to at least one surface mount attenuator board 318. For example, the second flexible circuit board(s) 316 can be coupled to the surface mount attenuator board(s) 318 by at least one flexible-to-flexible interconnect 336. For example, the flexible-to-flexible interconnect(s) 336 can structurally and / or electrically couple the ground layer(s), dielectric layer(s), and / or signal line(s) of the second flexible circuit board 316 to the surface mount attenuator board 318. As an example, the flexible-to-flexible interconnect(s) 336 can be formed by soldering, brazing, and / or otherwise fusing components of the second flexible circuit board 316 to the surface mount attenuator board 318. The flexible-to-flexible interconnect(s) 336 can be or can include any suitable interconnect of two flexible circuit boards 306, such as a butt joint, a lap joint, and / or any other suitable interconnect.

[0068] The surface mount attenuator board 318 can be a flexible printed circuit board. In some embodiments, the surface mount attenuator board(s) 318 can be or can include a surface mount attenuator board material at the ground layer(s) and / or signal line(s). The surface mount attenuator board material can be selected to provide high signal transfer performance characteristics. For example, the surface mount attenuator board material can be or can include copper, brass, gold, and / or other suitable materials having high signal transfer performance characteristics. For example, the surface mount attenuator board can include copper signal lines and / or ground layer(s) to provide high signal transfer performance characteristics.

[0069] The surface mount attenuator board(s) 318 can include one or more surface mount attenuators 354. The surface mount attenuator(s) 354 can be configured to attenuate or block thermophoton interference. In some embodiments, the surface mount attenuator board(s) 318 and / or the surface mount attenuator(s) 354 can be placed at a temperature cold enough that the surface mount attenuator(s) 354 do not produce thermophotons. In some embodiments, the surface mount attenuator(s) 354 can be disposed in an isolation board. The isolation board can be configured to isolate one or more surface mount attenuators. The isolation board can be attached to the surface mount attenuator board(s) 318. In some embodiments, the isolation board can be mounted to a ground layer and / or ground. The isolation board can include one or more cavities configured to isolate a first surface mount attenuator from a second surface mount attenuator. For example, the cavity can surround the first surface mount attenuator in a direction of the second surface mount attenuator and block crosstalk between the attenuators.

[0070] The quantum computing system 300 can include at least one third flexible circuit board 320. For example, the surface mount attenuator board(s) 318 can be coupled to the third flexible circuit board(s) 320 by at least one flexible-flex interconnect 338. For example, the flexible-flex interconnect(s) 338 can couple the ground layer(s), dielectric layer(s), and / or signal line(s) of the surface mount attenuator board 318 to the third flexible circuit board 320 (structurally and / or electrically). As an example, the flexible-flex interconnect(s) 338 can be formed by soldering, brazing, and / or fusing components of the surface mount attenuator board 318 to the third flexible circuit board 320. The flexible-flex interconnect(s) 338 can be or can include any suitable interconnect of two flexible circuit boards 306, such as a butt joint, a lap joint, and / or any other suitable interconnect.

[0071] The third flexible circuit board(s) 320 can be located at a point in the vacuum chamber at which the cooling gradient is cold enough that some materials exhibit superconductivity. For example, at least a portion of the third flexible circuit board(s) 320 can have a temperature below approximately 3 Kelvin.

[0072] In some embodiments, the third flexible circuit board(s) 320 can be or can include a third flexible circuit board material at the ground plane(s) and / or signal line(s). The third flexible circuit board 320 material can be selected to be superconductive at temperatures at which at least a portion of the third flexible circuit board(s) 320 experiences superconductivity. As an example, the third flexible circuit board(s) 320 material can be or can include niobium, tin, aluminum, and / or other suitable superconductive materials. For example, the third flexible circuit board(s) 320 can include copper-coated niobium signal lines and / or ground planes to provide superconductivity. For example, the copper plated on the third flexible circuit board(s) 320 can be used to interface with the superconductive niobium, which can provide improved signal transfer characteristics. In some embodiments, the copper-coated niobium board can be formed by first applying a layer of niobium, then applying a thin layer of copper to prevent oxide formation, and then applying a thicker layer of copper.

[0073] In some embodiments, the third flexible circuit board(s) 320 can be coupled to at least one fourth flexible circuit board 322. The third flexible circuit board(s) 320 can be coupled to the fourth flexible circuit board(s) 322 by at least one flexible-flex interconnect 340. For example, the flexible-flex interconnect(s) 340 can couple the ground plane(s), dielectric layer(s), and / or signal line(s) of the third flexible circuit board 320 to the fourth flexible circuit board 322 (structurally and / or electrically). As an example, the flexible-flex interconnect(s) 340 can be formed by soldering, brazing, and / or fusing components of the third flexible circuit board 320 to the fourth flexible circuit board 322. The flexible-flex interconnect(s) 340 can be or can include any suitable interconnect of two flexible circuit boards 306, such as a butt joint, a lap joint, and / or any other suitable interconnect.

[0074] The fourth flexible circuit board(s) 322 can couple the third flexible circuit board(s) 320 to the quantum hardware 304. For example, a connector 342 at one end of the fourth flexible circuit board(s) 322 can be attached to a port in signal communication with the quantum hardware 304. As one example, the connector can be a T-joint connector, such as a T-joint connector including a superconductive material (e.g., tin). Additionally and / or alternatively, the connector 342 can be a flat spring array.

[0075] In some embodiments, the fourth flexible circuit board(s) 322 can be or can include a fourth flexible circuit board material at the ground layer(s) and / or signal line(s). The fourth flexible circuit board 322 material can be selected to provide high signal transfer performance characteristics. As an example, the fourth flexible circuit board(s) 322 material can be or can include copper, brass, gold, and / or other suitable materials having high signal transfer performance characteristics. For example, the fourth flexible circuit board(s) 322 can include copper signal lines and / or ground layer(s) to provide high signal transfer performance characteristics. Additionally and / or alternatively, the fourth flexible circuit board(s) 322 material can be selected to be superconductive at temperatures at which at least a portion of the fourth flexible circuit board(s) 322 experiences superconductivity. As an example, the fourth flexible circuit board(s) 322 material can be or can include niobium, tin, aluminum, and / or other suitable superconductive materials.

[0076] According to example aspects of the present disclosure, the fourth flexible circuit board(s) 322 can be or can include a filter 356, such as an XYZ and / or IR filter 356. The filter 356 can include a laminated circuit assembly according to any of the embodiments described herein. For example, the filter 356 can be configured to reduce the effects of noise, thermal photons, and / or other potential sources of interference. As one example, the filter 356 can include a cavity in the fourth flexible circuit board(s) 322 filled with a filter material, such as a particulate suspension, for providing XYZ / infrared filtering. In some examples, the filter material can provide less attenuation of signals at a first frequency and greater attenuation of signals at a second, higher frequency. For example, some filter materials provide attenuation that increases in a substantially monotonic manner as the frequency of a signal increases for at least a portion of a target frequency band. In some embodiments, aspects of the filter material can be configured for low pass operation and / or band pass operation.

[0077] Figure 3 An example laminated circuit assembly that can be used to implement a filter according to example embodiments of the present disclosure is depicted. The laminated circuit assembly 100 includes a signal line 102 within a substrate 104. In the depicted embodiment, planar conductors 106a and 106b are laminated to the upper and lower surfaces of the substrate 104, respectively, although it is contemplated that either of the planar conductors 106a and 106b can be replaced with other conductor geometries and / or omitted. For example, Figure 3The embodiments depicted in the middle can correspond to a "stripline" configuration, in which the signal line 102 comprises a conductive trace extending in the x-direction between two parallel planar conductors, although the systems and methods of the present disclosure can include embodiments having other circuit configurations, including "microstrip" configurations and substantially any configuration of one or more conductors 102 (which can be traces, wires, etc.) and a substrate 104 (e.g., typically a circuit board, such as a single-, double-, and / or multi-layer printed circuit board).

[0078] In some embodiments, the signal line 102 can comprise one or more conductive materials (e.g., copper, gold, silver, aluminum, tin, zinc, niobium, palladium, platinum, titanium, tungsten, vanadium, magnesium, molybdenum, magnesium diboride, etc.) that have been formed into a conductor, such as a stripline or trace. For example, the signal line 102 can comprise multiple conductive materials in an alloy and / or composite formulation.

[0079] In some embodiments, the signal line 102 can comprise multiple layers of conductive material. In one example, the signal line 102 can comprise at least one layer of superconducting material (e.g., superconducting at temperatures below about 3 Kelvin, such as below about 1 Kelvin, such as below about 20 milli-Kelvin, such as niobium). In some embodiments, the superconducting material can be laminated with another conductor. For example, a superconducting layer can be deposited (such as by vacuum deposition) on a surface of a substrate, while another layer (e.g., a copper layer, a tin layer, etc.) can be deposited on a surface of the superconducting conductor. In some embodiments, another layer can be deposited on the superconducting layer to provide protection to the superconducting layer (e.g., from oxidation). For example, a first deposition can deposit a superconducting material onto a substrate in a vacuum environment, and without releasing the vacuum, a second deposition can deposit another conductor to shield the superconducting material from the atmosphere. In some embodiments, one or more additional layers of conductive material (e.g., the same or different conductive material) can be plated on top of the deposited layers. For example, the second deposition can provide a thin protective coating for the superconductor, and a subsequent plating (e.g., electroplating) can provide a thicker conductive layer. In some example aspects, the thicker plated conductive layer can provide structural support to improve the strength and / or resiliency of the superconducting layer(s) of the signal line 102. In some embodiments, one or more of the planar conductors 106a and 106b (and any plated vias associated therewith) can be similarly shaped using one or more deposited layers and one or more plated layers.

[0080] In some embodiments, the signal line 102 can be deposited or otherwise laminated on a substrate. In some embodiments, the signal line 102 can be embedded within a substrate. For example, one or more layers of a polymeric substrate can be fused or otherwise interfaced such that any signal line 102 on a surface of one of the layers can be embedded within the entire substrate. Figure 3An example is shown in which the signal line 102 is embedded within the substrate 104 and extends in the x-direction.

[0081] In some embodiments, the substrate 104 can include one or more polymers. In some implementations, the substrate 104 can include a reinforced polymer, such as a fiber-reinforced polymer (e.g., glass fiber). In some embodiments, the substrate 104 can include a filled polymer. In some embodiments, the substrate can be loaded with a filler including frequency absorbing particles.

[0082] In some embodiments, the substrate 104 can include a filter portion. For example, a portion of the substrate 104 can include a filter for filtering a signal propagating along the signal line 102 (e.g., along a transmission line including the signal line 102 and / or the planar conductors 106a and 106b, if present). The filter portion can include a filter material that filters the signal. The filter material can be the same as or different from the material of the substrate 104. For example, in one embodiment, the filter portion includes a portion of the substrate 104 that surrounds and / or is adjacent to the signal line 102, and that portion can be loaded with frequency absorbing particles to provide a desired filtering effect to a signal on the signal line 102. In some embodiments, the substrate 104 can be loaded with frequency absorbing particles to provide a filtering effect.

[0083] In some embodiments, a cavity can be formed within the substrate 104 that can be filled with a filter material that is different from the substrate 104. For example, a dielectric portion can be formed from a first polymer. The frequency absorbing material can include frequency absorbing particles embedded within a second polymer (e.g., a curable polymer) that is different from the first polymer. As one example, the cavity can be filled with the curable polymer when the curable polymer is in an uncured state.

[0084] In general, the cavity can be formed according to any suitable method. For example, the cavity can be formed by removing material within the substrate 104. However, it is also contemplated that the cavity can be formed by selectively omitting the substrate 104 in an area where the filter material is intended to be placed. For example, as described above, the substrate 104 can be formed from multiple layers, and one or more of the layers can include voids that, when interfaced with an adjacent layer, provide a cavity within the substrate 104 that can be filled with the filter material. In some embodiments, the substrate 104 can be formed using an additive manufacturing technique, and one or more portions of the substrate 104 can be selectively not added during the manufacturing, thereby forming a cavity.

[0085] In some embodiments, the cavity can be formed in the substrate 104 by machining an existing laminated circuit assembly. For example, in Figure 3The diagram depicts a laminated circuit assembly 100, which can be processed according to exemplary aspects of this disclosure. In some embodiments, processing may include removing a portion of one or more layers of material that may be laminated to a substrate 104. For example, in Figure 4 In this design, the laminated circuit assembly 100 is depicted as a portion of the planar conductor 106a being removed, thereby exposing region 108 of the substrate 104. Although Figure 4 The exposed area 108 is depicted as rectangular; however, it should be understood that the exposed area 108 can take virtually any form, and because some embodiments may lack the planar conductor 106a, the exposed area 108 can essentially take the form of the surface of the substrate 104. The exposed area 108 can provide an entry point for removing material from the substrate 104.

[0086] In some embodiments, the processing may include removing a portion of the substrate 104 to form a cavity that can be partially or completely filled with filter material. For example, Figure 5 A laminated circuit assembly 100 is depicted with a portion of the substrate 104 removed along length 110, width 112, and depth 114.

[0087] In some embodiments, portions of the substrate 104 may be mechanically removed by cutting, drilling, milling, grinding, or otherwise. In some embodiments, portions of the substrate 104 may be removed by etching or other chemically reactive material removal processes. In some embodiments, portions of the substrate 104 may be removed by ablation to form cavities (e.g., laser ablation, etc.). For example, as... Figure 5 As shown, material can be removed from substrate 104 in one direction (e.g., from the y-direction as shown). For example, material from substrate 104 can be selectively removed from above signal line 102 in the y-direction and from beside signal line 102 in the z-direction. In some examples, depending on the material removal method, the composition of the coating on signal line 102 and / or thereon may affect the selective removal of material. For example, in some embodiments, the material(s) of signal line 102 may be resistant to the removal process (or at least more resistant than the material surrounding substrate 104). In this way, the material removal process can be applied to the area covered by length 110 and width 112 without shielding the area above signal line 102. For example, the material of signal line 102 may be resistant to an ablation process, such that the area covered by length 110 and width 112 can be ablated without shielding the area above signal line 102. In this way, the speed and throughput of the ablation process(s) can be improved.

[0088] like Figure 6As depicted, after material of the substrate 104 is removed, the cavity thus formed can be filled with a filter material to form a filter portion 116 of the substrate 104. As Figure 6 depicted, the filter portion 116 can be filled completely, or in some examples, partially. For example, the filter portion 116 can be filled with a first filter material and a second filter material, each filter material partially filling the cavity. In some embodiments, the filter material can partially fill the cavity (e.g., directly surrounding a portion of the signal line 102), and another material (e.g., material of the substrate 104) can fill in the remaining portion of the cavity to encapsulate the filter material. The filter portion 116 can extend to a surface of the substrate 104 and / or to an outer surface of a planar conductor laminated to the substrate 104 (e.g., as Figure 6 depicted).

[0089] Figure 7 A cross-sectional view of the filter portion 116 within the substrate 104 is depicted. The filter portion 116 can take substantially any shape defined by one or more boundaries of a cavity formed within the substrate 104. For example, one boundary can be defined based on a depth 118 of the signal line 102 within the substrate 104. Another boundary can be configured to extend a leg of the filter portion 116 an additional depth 120 to encompass the signal line 102, such that the leg can cover a thickness 122 of the signal line 102 plus another distance 124 beyond the thickness 122 of the signal line 102. In this way, the filter portion 116 can at least partially surround the signal line 102 to filter one or more signals propagating along the signal line 102. Additionally, a width 112 of the cavity can be configured such that the filter portion 116 can extend beyond a width 128 of the signal line 102 a distance 126 on one or both sides of the signal line 102. In some examples, the filter portion 116 extends at least the distance 126 on both sides of the signal line 102, but can optionally extend a longer distance on one side of the signal line 102 than the distance 126 on the other side to provide additional filtering and / or shielding on one side (e.g., to reduce crosstalk and / or other interference from another signal line near the one side).

[0090] Although the foregoing description has referred to figures depicting cavities formed that expose the signal line 102, it is contemplated that cavities can be formed that do not expose the signal line 102 according to other example aspects of the present disclosure. For example, in some cases, it can be desirable to form the cavities in one process (e.g., with one set of equipment) and transfer the processed substrate 104 to another system for further processing. In one embodiment, it can be desirable to retain at least some substrate material to protect and / or shield the signal line 102 from damage and / or contamination. For example, in some embodiments, as the filter material of the filter portion is filling the cavity (e.g., during insertion and / or injection, during adhesion of the filter material, and / or during solidification of the filter material, etc.), the filter material can exert mechanical stress on the signal line 102. In some cases, it can be desirable to retain at least some substrate material of the substrate 104 as a support for the signal line.

[0091] For example, Figure 8 A cross-sectional view of a circuit assembly 200 is depicted with another profile of the filter portion 116 that does not extend to the signal line 102, but is separated from the top portion of the signal line 102 by a distance 230. Similarly, in some embodiments, the pins of the filter portion 116 can be separated by a distance 232 that can be greater than the width 128 of the signal line 102 to leave some material of the substrate 104 surrounding the signal line 102.

[0092] Although the foregoing description has referred to figures depicting removal of material from the substrate 104 from one side (e.g., one outer surface) of the substrate, it is contemplated that material can be removed from both sides (e.g., above and below the signal line 102 in the y-direction). For example, Figure 9 A circuit assembly 250 is depicted with another profile of the filter portion 116. A cavity can be formed within the substrate 104 that separates the substrate 104 into two portions 104a and 104b (at least in the depicted viewing plane; in some embodiments, the portions 104a and 104b can be connected beyond the view). In some embodiments, the cavity can be formed by removing material from both sides of the circuit assembly 250 (e.g., by removing regions of the planar conductor 106a (if present), and / or by removing regions of the planar conductor 106b (if present)). In this way, a substantially symmetric cavity can be formed (e.g., reflectionally symmetric about the signal line 102).

[0093] In some embodiments, the cavity can extend to one or more (e.g., all) surfaces of the signal line 102 such that no substrate material from the substrate 104 remains within the filter portion 116 (e.g., as depicted in FIG. 2A). In some embodiments, the cavity can extend to one or more (e.g., all) surfaces of the signal line 102 such that no substrate material from the substrate 104 remains within the filter portion 116 (e.g., as depicted in FIG. 2A). Figure 10circuit assembly 50, as shown, with the cavity extension depth 118a and 118b abutting the signal line 102). However, in some embodiments, such as Figure 9 As shown, dielectric supports 256a and 256b can be provided (e.g., without removing the base material). The dielectric supports 256a and 256b can be configured to be the same or different, respectively (e.g., the support heights 256a and 256b can be the same or different). In this way, supports can be provided for the signal line 102 to support the signal line during subsequent processing (e.g., filling the filter portion 116 with filter material, etc.). The dielectric supports 256a and 256b can comprise a portion of the dielectric that is not removed during formation of the cavity.

[0094] Figure 9 Cover 258a and 258b, which can be used to cover the entrance for forming the cavity within the base 104, are also depicted. One or both of the covers 258a and 258b can comprise a conductive material. In one embodiment, the covers 258a and 258b are included within the planar conductors 106a and 106b, respectively (e.g., the planar conductors 106a and / or 106b can be laminated to the base 104 after the filter portion 116 is formed). In some embodiments, another conductor (e.g., another planar conductor) can be applied or laminated over the entrance(s) to form at least one of the covers 258a and 258b. For example, a conductive paint or other coating can be applied. The conductive coating can be dried and / or cured in place to provide one or both of the covers 258a and 258b.

[0095] In some embodiments, in accordance with example aspects of the present disclosure, any one, subset, or all of the above communications can be conveyed via one or more signals propagating along the filtered signal lines 102 described herein. For example, in one embodiment, the filtered signal lines 102 in accordance with example aspects of the present disclosure can be used to convey qubit interface signals from a control device for controlling and / or reading the behavior of one or more qubits. For example, in one embodiment, the signal lines 102 can be used to convey one or more signals associated with Pauli X, Y, and / or Z operators.

[0096] In one embodiment, a quantum computing system includes a qubit and a signal line 102 associated with the qubit. The signal line 102 and the qubit can be configured and arranged such that, during operation of the quantum computing device, the signal line 102 allows coupling of XY qubit control flux bias in a first frequency range. The signal line 102 can also provide coupling of Z qubit control flux bias in a second frequency range. In some embodiments, attenuation of the signal(s) propagating along the signal line 102 can be configured to avoid excessive Joule heating caused by excessive attenuation of signals in different frequency ranges. For example, the dimensions and / or filtering material of filter portion 116 can be configured such that filter portion 116 can include a frequency-absorbing material that provides less attenuation of signals at a first frequency, while providing greater attenuation of signals at a different second frequency (e.g., which can be higher or lower). For example, some filtering materials provide attenuation that increases in a substantially monotonic manner with increasing signal frequency for at least a portion of a target frequency band.

[0097] In some embodiments, aspects of the filtering material can be configured for low pass operation and / or band pass operation. For example, in one embodiment, filter portion 116 can be configured to attenuate at a first level of attenuation in a 0 to 0.5 GHz frequency band, and at a second level of attenuation in a 2 to 8 GHz frequency band. While XY control signals can operate in the microwave frequency band, in some cases Z control signals (which, in some examples, can be higher power signals than XY control signals) can operate in the 0 to 0.5 GHz frequency band in some cases. Excessive attenuation of Z qubit control signals can result in substantial Joule heating within the attenuator. Such heating in turn can increase noise and make it difficult to maintain cryogenic temperatures necessary to provide superconducting operation of circuit elements of the qubits. For example, Joule heating can increase or exceed the cooling power of a cryostat or cryostat stage in which the qubits are operating. In some embodiments, filter portion 116 can be configured to attenuate signals greater than approximately 10 GHz at a greater level of attenuation than the attenuation provided to the 0 to 0.5 GHz frequency band and the 2 to 8 GHz frequency band, in order to attenuate thermal radiation (e.g., infrared signals) passing through and / or propagating along the signal line.

[0098] Figure 11 A flow diagram of an example method 600 according to example embodiments of the present disclosure is depicted. For purposes of illustration and discussion, Figure 11 Steps are depicted in a particular order. Using the disclosure provided herein, one of ordinary skill in the art will understand that individual steps of any of the methods disclosed herein can be adapted, modified, performed concurrently, omitted, include steps not shown, rearranged, and / or extended in various ways without departing from the scope of the present disclosure.

[0099] At 602, the method can include receiving or obtaining a laminated circuit assembly. The laminated circuit assembly can be constructed in accordance with any of the example embodiments disclosed herein. The laminated circuit assembly can include one or more signal lines disposed in a first direction within a dielectric material of a substrate. The laminated circuit assembly can define a second direction perpendicular to the substrate and a third direction orthogonal to the first direction and the second direction.

[0100] At 604, the method can include forming a cavity within the substrate by removing a portion of the dielectric material over the signal line in the second direction. The cavity can extend in the first direction along the signal line.

[0101] At 606, the method can include filling the cavity with a frequency absorbing material. The frequency absorbing material can be configured in accordance with any of the embodiments disclosed herein. The frequency absorbing material can provide less attenuation to a first signal at a first frequency than to a second signal at a higher second frequency. The filled cavity can be configured to attenuate an infrared signal passing through the one or more signal lines.

[0102] Additional disclosure

[0103] The digital and / or quantum subject matter described in this specification 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, but is not limited to, a quantum computer / computing system, a quantum information processing system, a quantum cryptography system, or a quantum simulator.

[0104] Implementations of the digital and / or quantum subject matter described in this specification can be implemented as one or more digital and / or quantum computer program(s), 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 suitable receiver apparatus for execution by a data processing apparatus.

[0105] The terms quantum information and quantum data refer to information or data carried by, held or stored by a quantum system, where the smallest non-trivial system is a qubit, i.e. a system defining a unit of quantum information. It will be appreciated that the term “qubit” encompasses all quantum systems that can be suitably approximated as a two-level system in the respective context. Such quantum systems can include multi-level systems, e.g. having two or more levels. By way of example, such systems can include atoms, electrons, photons, ions or superconducting qubits. In many implementations, the computational ground state makes use of the ground state and the first excited state for identification, however it will be appreciated that other arrangements are possible in which the computational state makes use of higher level excited states for identification.

[0106] 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), an ASIC (application specific integrated circuit), or a quantum simulator, i.e. a quantum data processing apparatus designed to simulate or produce information 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-purpose 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.

[0107] A digital computer program (which can also be referred to or described as a program, software, a software application, a module, a software module, a 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, a software application, a module, a software module, a script, or code) can be written in any form of programming language, including compiled or interpreted languages, or declarative or procedural languages, and be translated into a suitable quantum programming language or be written in a quantum programming language, e.g. QCL, Quipper, etc.

[0108] 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 is used by the operating system to store an application program, in a file that is dedicated to storing computer programs or in multiple cooperating files. A digital and / or quantum computer program can be deployed to be executed by one digital or one quantum computer or distributed over a number of digital and / or quantum computers that are functionally coupled via a digital and / or quantum data communication network. A quantum data communication network is understood to be a network that can transmit quantum data using quantum systems (e.g., qubits). Typically, a digital data communication network cannot transmit quantum data, however a quantum data communication network can transmit quantum data and digital data.

[0109] The processes and logic flows described in this specification can be performed by one or more programmable digital and / or quantum computers, operating with one or more digital and / or quantum processors, executing 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, and apparatus can also be implemented as, special purpose logic circuitry, or a combination of special purpose logic circuitry or quantum emulators and one or more programmed digital and / or quantum computers, such as, for example, an FPGA, an ASIC, or a quantum emulator.

[0110] For a system of one or more digital and / or quantum computers, “configured to” perform particular operations or actions means that the system has been designed or modified to perform those operations or actions in response to instructions from a digital and / or quantum data processing apparatus. For one or more digital and / or quantum computer programs, “configured to” perform particular operations or actions means that the one or more programs include instructions that, when executed by a digital and / or quantum data processing apparatus, cause the apparatus to perform those operations or actions. A quantum computer can receive instructions from a digital computer that, when executed by the quantum computing apparatus, cause the apparatus to perform those operations or actions.

[0111] 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, a random access memory, or a quantum system suitable for transmitting quantum data (e.g., photons), or a combination thereof.

[0112] Some example elements of a digital and / or quantum computer are a central processing unit for running 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 into, special purpose logic circuitry or quantum simulators. A digital and / or quantum computer will normally also include, or be operatively coupled to, one or more mass storage devices for storing digital and / or quantum data (e.g., magnetic, magneto-optical or optical disks, or quantum systems suitable for storing quantum information), to receive digital and / or quantum data from the mass storage device, or to transfer digital and / or quantum data to the mass storage device, or both. However, a digital and / or quantum computer need not have such devices.

[0113] 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 such as internal hard disks or removable disks; magneto-optical disks; CD-ROM and DVD-ROM disks; and quantum systems such as trapped atoms or electrons. It is to be appreciated that quantum memory is a device capable of storing quantum data with high fidelity, efficiently, and for long periods of time, e.g., an optical-matter interface in which light is used for transmission and matter is used to store and preserve quantum data quantum features such as superposition or quantum coherence.

[0114] The control of the various systems described in this specification, or portions of them, can be implemented in a digital and / or quantum computer program product that includes instructions that are stored in one or more non-transitory machine-readable storage media and that are executable on one or more digital and / or quantum processing devices. The systems described in this specification, or portions of them, can each be implemented as a device, method, or electronic system that can include one or more digital and / or quantum processing devices and a memory for storing executable instructions to perform the operations described in this specification.

[0115] While this specification contains many specifics, these should not be construed as limitations on the scope of the application, but rather as descriptions of particular implementations thereof. Certain features that are, for clarity, described above in the context of separate implementations can also be provided in combinations thereof. Conversely, various features that are, for brevity, described above in the context of a single implementation can also be provided separately or in any suitable subcombination. In addition, while features can be described above as being implemented 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 subsystem.

[0116] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring such order nor that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing can be advantageous. 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 together in a single software product or packaged into multiple software products.

[0117] 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 do not necessarily require the particular order or sequential ordering shown and / or described, to achieve the desired results. In some cases multitasking and parallel processing can be advantageous.

Claims

1. A laminated circuit assembly, comprising: One or more signal lines are disposed within the substrate in the first direction; The dielectric portion of the substrate; as well as The filter portion of the substrate extends in the first direction and includes a frequency absorption material that provides less attenuation to a first signal at a first frequency compared to a second signal at a higher second frequency; The filter section is configured to attenuate the infrared signal passing through the one or more signal lines, and The filter portion includes a boundary defined by a cavity formed within the dielectric portion, wherein the cavity exposes at least a portion of the one or more signal lines, and wherein the cavity is at least partially filled with the frequency absorbing material such that the frequency absorbing material is in physical contact with at least a portion of the one or more signal lines.

2. The laminated circuit assembly according to claim 1, wherein: The one or more signal lines are configured to transmit control signals from classical computing devices to quantum hardware.

3. The laminated circuit assembly according to claim 1, wherein, The dielectric portion is formed of a polymer, and the filter portion includes frequency-absorbing particles embedded within the polymer.

4. The laminated circuit assembly according to claim 1, wherein, The dielectric portion is formed of a first polymer, and the frequency absorbing material comprises frequency absorbing particles embedded in a second polymer that is different from the first polymer.

5. The laminated circuit assembly according to claim 1, wherein: The second direction is perpendicular to the base, and the third direction is orthogonal to both the first and second directions; and The first portion of the cavity is located above the signal line along the second direction, and the second portion of the cavity is located next to the signal line along the third direction.

6. The laminated circuit assembly according to claim 5, wherein, The first portion of the cavity extends from the outer surface of the substrate to the signal line.

7. The laminated circuit assembly according to claim 5, comprising: A dielectric support member supporting the signal line, the dielectric support member including a portion of the dielectric forming the cavity therein; The third portion of the cavity is located below the signal line along the second direction.

8. The laminated circuit assembly according to claim 5, comprising: A first conductive layer laminated to the outer surface of the substrate, the first conductive layer including an inlet for filling the cavity with the frequency absorbing material; as well as A second conductive layer covering the inlet.

9. The laminated circuit assembly according to claim 8, wherein, The second conductive layer includes a curable non-metallic substrate.

10. The laminated circuit assembly according to claim 4, wherein, The second polymer is a curable polymer, and the cavity has been at least partially filled by the frequency-absorbing material while the second polymer is in an uncured state.

11. The laminated circuit assembly according to claim 1, wherein, The one or more signal lines include: A first signal line, having a first filter section corresponding to the first signal line; and The second adjacent signal line has a second filter section corresponding to the second adjacent signal line; The first filter portion and the second filter portion are offset from each other in the first direction.

12. The laminated circuit assembly according to claim 1, wherein, The filter section is configured to attenuate the signal in at least one of the one or more signal lines by at least 0.5 dB / GHz.

13. The laminated circuit assembly according to claim 1, wherein, The cavity is formed by ablation of the dielectric.

14. The laminated circuit assembly according to claim 1, wherein, The first frequency is less than 500 MHz, and the second frequency is greater than 2 GHz and less than 8 GHz, wherein the frequency absorbing material provides attenuation to the infrared signal greater than attenuation to the first signal or the second signal.

15. A method for manufacturing a filter for a signal line, comprising: Receive a laminated circuit assembly, the laminated circuit assembly including one or more signal lines disposed in a first direction within a dielectric material of a substrate, wherein a second direction is perpendicular to the substrate, and a third direction is orthogonal to the first direction and the second direction; A cavity is formed within the substrate by removing a portion of the dielectric material above the signal line in the second direction, the cavity extending along the signal line in the first direction, wherein the cavity exposes at least a portion of the one or more signal lines; and The cavity is filled with a frequency-absorbing material such that the frequency-absorbing material is in physical contact with at least a portion of the one or more signal lines, wherein the frequency-absorbing material provides less attenuation for a first signal at a first frequency than for a second signal at a higher second frequency, and wherein the filled cavity is configured to attenuate infrared signals passing through the one or more signal lines.

16. The method according to claim 15, wherein, The cavity is formed by ablation of the dielectric material.

17. The method of claim 15, further comprising: A conductive layer is laminated onto the outer surface of the substrate, the conductive layer covering the inlet for filling the cavity with the frequency absorbing material.

18. A cryogenic cooling system, comprising: Multiple cooling stages are configured to cool the cooling portion of the computing system to temperatures below 3 Kelvin; One or more signal lines are coupled to the control unit and connected to the cooling section of the computing system; as well as Laminated circuit assembly, including: One or more signal lines are disposed within the substrate in the first direction; The dielectric portion of the substrate; and The filter portion of the substrate extends in a first direction and includes a frequency absorption material that provides less attenuation to a first signal at a first frequency than to a second signal at a higher second frequency; The filter section is configured to attenuate the infrared signal passing through the one or more signal lines, and The filter portion includes a boundary defined by a cavity formed within the dielectric portion, wherein the cavity exposes at least a portion of the one or more signal lines, and wherein the cavity is at least partially filled with the frequency absorbing material such that the frequency absorbing material is in physical contact with at least a portion of the one or more signal lines.

19. The cryogenic cooling system according to claim 18, wherein, One or more of the plurality of cooling stages are configured to provide cooling at temperatures less than 20 milliklvin and include the laminated circuit assembly.

Images