A superconducting qubit measurement scheme using low-frequency microwave signals in a dilution refrigerator

Abstract

A technique for measuring superconducting qubits using low-frequency microwave signals within a dilution refrigerator is provided. In one example, a cryogenic microwave system for measuring superconducting qubits using microwave signals includes a dilution refrigerator system for a quantum processor. The dilution refrigerator system converts a microwave signal associated with qubit information into a reduced-frequency microwave signal based on a Josephson mixer circuit located within the dilution refrigerator system. The reduced-frequency microwave signal includes a frequency lower than the qubit frequency and a readout resonator frequency associated with the quantum processor.

Description

Background Art

[0001] The present subject matter relates to quantum hardware and, more particularly, to superconducting devices for quantum computing. Summary of the invention

[0002] The following is a summary presented to provide a basic understanding of one or more embodiments of the invention. This summary is not intended to identify key or important elements of any scope of a particular embodiment or any scope of the claims. Its sole purpose is to present concepts in a simplified form as a prelude to the more detailed description that is presented later. In one or more embodiments described herein, an apparatus, system, method, device, and / or computer program product is described that facilitates a measurement scheme for superconducting qubits using low frequency microwave signals within a dilution refrigerator.

[0003] According to one embodiment, a cryogenic microwave system for measuring superconducting qubits using microwave signals may include a dilution refrigerator system for a quantum processor. The dilution refrigerator system may convert a microwave signal associated with qubit information into a reduced frequency microwave signal based on a Josephson mixer circuit located within the dilution refrigerator system. The reduced frequency microwave signal may include a frequency lower than the qubit frequency and a readout resonator frequency associated with the quantum processor.

[0004]

[0013] According to another embodiment, a system may include a dilution refrigerator system for a quantum processor. The dilution refrigerator system may reduce and increase the frequency of a microwave signal associated with a qubit readout to provide qubit measurements associated with the quantum processor.

[0005] According to yet another embodiment, a method is provided. The method may include converting a microwave signal into a microwave signal of reduced frequency by a dilution refrigerator system associated with a quantum processor based on a Josephson mixer circuit located within the dilution refrigerator system. The method may also include digitizing the microwave signal of reduced frequency into a digital signal including qubit information associated with the quantum processor by the dilution refrigerator system. Furthermore, the method may include transmitting the digital signal to a classical computing system by the dilution refrigerator system.

[0006] According to yet another embodiment, a system may include a Josephson mixer circuit and a fast single-pass quantum (RSFQ) analog-to-digital converter (ADC). The Josephson mixer circuit may convert a first microwave signal associated with quantum information generated by a quantum processor into a second microwave signal, wherein a first frequency associated with the first microwave signal is greater than a second frequency associated with the second microwave signal. The RSFQ ADC may digitize the second microwave signal based on a superconducting device to generate a digital signal for a classical computing system.

[0007] According to yet another embodiment, a system may include a quantum processor and a dilution refrigerator system. The dilution refrigerator system may reduce the frequency of a first microwave signal associated with a qubit readout via a Josephson mixer circuit to generate a second microwave signal. The dilution refrigerator system may also digitize the second microwave signal via a fast single-pass quantum (RSFQ) analog-to-digital converter (ADC) to generate a digital signal for a classical computing system. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 Exemplary non-limiting systems associated with a dilution refrigerator system, a quantum processor, and a classical computing system are shown according to one or more embodiments described herein.

[0009] Figure 2 Another exemplary non-limiting system associated with a dilution refrigerator system, a quantum processor, and a classical computing system according to one or more embodiments described herein is shown.

[0010] Figure 3 Yet another exemplary non-limiting system associated with a dilution refrigerator system, a quantum processor, and a classical computing system according to one or more embodiments described herein is shown.

[0011] Figure 4 Yet another exemplary non-limiting system associated with a dilution refrigerator system, a quantum processor, and a classical computing system according to one or more embodiments described herein is shown.

[0012] Figure 5 Yet another exemplary non-limiting system associated with a dilution refrigerator system, a quantum processor, and a classical computing system according to one or more embodiments described herein is shown.

[0013] Figure 6 Yet another exemplary non-limiting system associated with a dilution refrigerator system, a quantum processor, and a classical computing system according to one or more embodiments described herein is shown.

[0014] Figure 7 Yet another exemplary non-limiting system associated with a dilution refrigerator system, a quantum processor, and a classical computing system according to one or more embodiments described herein is shown.

[0015] Figure 8 An exemplary non-limiting system associated with a classical computing system according to one or more embodiments described herein is shown.

[0016] Fig. 9 An exemplary non-limiting system associated with a Josephson-based mixer according to one or more embodiments described herein is shown.

[0017] Fig.10 A flow chart is shown of an exemplary non-limiting computer-implemented method for providing an improved dilution refrigerator for a superconducting quantum processor according to one or more embodiments described herein. DETAILED DESCRIPTION

[0018] The following detailed description is illustrative only and is not intended to limit the application or use of the embodiments and / or embodiments. In addition, it is not intended to be bound by any express or implied information presented in the previous background technology or summary or detailed description.

[0019] One or more embodiments are now described with reference to the accompanying drawings, wherein the same reference numerals are used to represent the same elements throughout. In the following description, for the purpose of explanation, many specific details are set forth in order to provide a more thorough understanding of one or more embodiments. However, in various cases, it is apparent that one or more embodiments may be practiced without these specific details.

[0020] A superconductor device may be a device that provides zero resistance below a certain temperature. For example, a superconducting device may be employed as a qubit for a superconducting quantum processor. The superconducting quantum processor may be controlled and / or measured using one or more microwave signals, which are in a frequency range, for example, between 4 gigahertz (GHz) and 10 GHz. In addition, the superconducting quantum processor may be mounted on a dilution refrigerator, which may be cooled to a millikelvin temperature. In one embodiment, the superconducting quantum processor may be mounted on a base stage of a dilution refrigerator. The superconducting quantum processor may be cooled to a millikelvin temperature, so as to operate the superconducting quantum processor, for example, in a superconducting state. For example, in order to operate effectively, the temperature of the superconducting quantum processor needs to be lower than the critical temperature of the superconducting material employed in the superconducting quantum processor. In one embodiment, a superconducting quantum processor employing an aluminum-based Josephson junction needs to be cooled to below the critical temperature of aluminum (e.g., a temperature approximately equal to 1.2 Kelvin (K)) in order to operate effectively. Additionally or alternatively, the superconducting quantum processor may be cooled to millikelvin temperatures, for example, so as to suppress thermal noise in a superconducting microwave circuit of the superconducting quantum processor to an energy level below the microwave photon excitation of the superconducting microwave circuit. In order to achieve such ultra-low temperatures for the superconducting quantum processor, blackbody radiation noise and / or electromagnetic noise need to be blocked from reaching the superconducting quantum processor. Blackbody radiation noise and / or electromagnetic noise may come from outside the dilution refrigerator (e.g., from a room temperature environment) and / or from a higher temperature stage within the dilution refrigerator (e.g., a 4K stage within the dilution refrigerator). Typically, in order to reduce blackbody radiation noise and / or electromagnetic noise, a plurality of electromagnetic and / or blackbody radiation shields are incorporated into the dilution refrigerator. Additionally or alternatively, in order to reduce blackbody radiation noise and / or electromagnetic noise, different stages of the dilution refrigerator may be thermally isolated. Additionally or alternatively, to reduce blackbody radiation noise and / or electromagnetic noise, input lines within the dilution refrigerator (e.g., input lines that carry microwave signals from room temperature electronic devices to superconducting quantum processors) can incorporate lossy coaxial cables, attenuators, and / or filters. Additionally or alternatively, to reduce blackbody radiation noise and / or electromagnetic noise, output lines within the dilution refrigerator (e.g., output lines that carry microwave signals from superconducting quantum processors to room temperature electronic devices outside the dilution refrigerator) can incorporate filters and / or directional devices, such as isolators, circulators, semiconductor-based transistors, etc. However, reducing the blackbody radiation noise and / or electromagnetic noise of a superconducting quantum processor associated with a dilution refrigerator generally requires large hardware overhead. In addition, reducing the blackbody radiation noise and / or electromagnetic noise of a superconducting quantum processor associated with a dilution refrigerator generally introduces a large amount of heat load within the dilution refrigerator. Reducing the blackbody radiation noise and / or electromagnetic noise of a superconducting quantum processor associated with a dilution refrigerator generally consumes a large amount of power.In this way, reduction of blackbody radiation noise and / or electromagnetic noise of a superconducting quantum processor associated with a dilution refrigerator may be improved.

[0021] To address these and / or other problems, embodiments described herein include systems, methods, and / or computer program products that facilitate improvements in dilution refrigerator systems for superconducting quantum processors. For example, a novel measurement scheme for superconducting qubits using low-frequency microwave signals in a dilution refrigerator is provided herein. In one embodiment, a high-frequency output readout microwave signal carrying qubit information can be down-converted to a relatively low-frequency microwave signal. As used herein, a "high-frequency" microwave signal can be approximately 8 GHz or higher. In addition, as used herein, a "low-frequency" microwave signal can be approximately in the frequency range between 0.5 GHz and 2 GHz (e.g., lower than the qubit frequency and / or the readout resonator frequency), and a high-frequency output readout microwave signal can be a microwave signal received by a dilution refrigerator associated with a quantum processor (e.g., a superconducting quantum processor). The down-conversion process for the high-frequency output readout microwave signal can be lossless and / or coherent. In addition, a set of Josephson mixers can be used to perform the down-conversion process for the high-frequency output readout microwave signal. The set of Josephson mixers can be, for example, dissipative three-wave Josephson mixers. The qubit readout signal transmitted by the readout resonator can also be amplified, using, for example, a quantum confinement amplifier or a near quantum confinement amplifier at the base stage of the dilution refrigerator. Amplification of the qubit readout signal can be performed on the original qubit readout signal (e.g., before the down-conversion process). Alternatively, amplification of the qubit readout signal can be performed on the down-converted qubit readout signal (e.g., after the down-conversion process). The original qubit readout signal can be amplified using, for example, a Josephson directional amplifier using flux bias and / or microwave drive. For example, a direct current superconducting quantum interference device (DC-SQUID) amplifier using direct current (DC) and / or flux bias can be used to amplify the down-converted qubit readout signal. In certain embodiments, a Josephson-based isolator or a Josephson-based circulator can be implemented between the qubit-resonator system and the directional amplifier of the dilution refrigerator to, for example, prevent excessive backlash of the directional amplifier on the qubit. The Josephson-based isolator and / or the Josephson-based circulator can be driven using flux bias and / or microwave. In some embodiments, a bandpass filter and / or a high pass filter can be implemented on the output line of the dilution refrigerator between the qubit-resonator system and the down conversion stage. The bandpass filter and / or the high pass filter transmits the high frequency readout signal with minimal insertion loss. The bandpass filter and / or the high pass filter can also block DC signals and microwave signals below a threshold frequency, where the threshold frequency is lower than the high frequency readout signal. In some embodiments, a low pass filter and / or a frequency dependent attenuator can be implemented on the output line of the dilution refrigerator, which is one or more different stages between the base stage of the dilution refrigerator and the 4K stage of the dilution refrigerator.In this way, the down-converted qubit readout signal can be transmitted through the output chain with little or no attenuation.Signals and / or noise at frequencies above the frequency of the down-converted qubit readout signal can also be attenuated.

[0022] In one embodiment, a fast single flux quantum (RSFQ) analog-to-digital converter (ADC) can be implemented in the 4K stage of the dilution refrigerator. The RSFQ ADC can sample and digitally down-convert the readout signal. In one aspect, the output of the RSFQ ADC can be a digital signal transmitted to a classical computing system. The classical computing system can include a room temperature processing unit for classical signal processing and / or classical signal analysis. Additionally or alternatively, the digital signal can be transmitted to the RSFQ logic located at the 4K stage of the dilution refrigerator. In certain embodiments, additionally or alternatively, an energy-saving RSFQ (ERSFQ) circuit can be implemented in the 4K stage of the dilution refrigerator. In certain embodiments, additionally or alternatively, an energy-saving single flux quantum (eSFQ) circuit can be implemented in the 4K stage of the dilution refrigerator. In certain embodiments, in embodiments where the high frequency microwave readout signal is approximately equal to the resonant frequency of the readout resonator of the qubit within the dilution refrigerator system, the input line for the dilution refrigerator can incorporate a microwave attenuator and / or filter. In some embodiments, the input line of the dilution refrigerator may incorporate a microwave attenuator and / or filter that attenuates high frequency microwave signals and / or noise above a threshold frequency in embodiments where the high frequency microwave signals and / or noise are detuned relative to the resonant frequency of the readout resonator of the dilution refrigerator. The threshold frequency may be below the resonant frequency of the readout resonator. In some embodiments, an up-conversion stage may be implemented into the dilution refrigerator-based base stage to up-convert a low frequency microwave qubit readout signal into a high frequency microwave qubit readout signal that is approximately equal to the resonator frequency of the readout resonator of the dilution refrigerator. The up-conversion process associated with the up-conversion stage may be performed using a set of Josephson mixers. The set of Josephson mixers may be, for example, dissipative three-wave Josephson mixers using flux bias and microwave drive. In one example, the set of Josephson mixers may employ a Josephson ring modulator coupled to a lumped element microwave resonator and a surface acoustic wave (SAW) resonator. In some embodiments, separate input lines for qubit control may be employed. In some embodiments, microwave pump lines within a dilution refrigerator are attenuated by noise at frequencies above or below the corresponding pump frequency. The microwave pump lines may carry the microwave drive required for operation of a Josephson mixer, a Josephson-based directional amplifier, a Josephson-based isolator, and / or a Josephson-based circulator within the dilution refrigerator. In some embodiments, the pump lines may be attenuated by employing bandpass filters on the pump lines that minimize attenuation of pump signals (e.g., in-band signals) and severely attenuate other signals (e.g., out-of-band signals). In this way, the hardware overhead of a dilution refrigerator system associated with a quantum processor may be reduced.For example, a dilution refrigerator system associated with a quantum processor can be implemented without a magnetic-based cryocirculator, an isolator, and / or a transistor (e.g., a high electron mobility transistor). In addition, a microwave mixer is not required at room temperature on the readout line. The reduced hardware overhead can also promote the scalability of the dilution refrigerator system. In addition, the heat load and / or mass load in the dilution refrigerator can be reduced. The power consumption of the dilution refrigerator system associated with the quantum processor can also be reduced. In addition, the input line for the dilution refrigerator and / or the output line for the dilution refrigerator can include an attenuator that attenuates blackbody radiation noise and / or electromagnetic noise. The synthesis and / or sampling of low-frequency microwave signals in the dilution refrigerator system associated with the quantum processor can also reduce the complexity of the dilution refrigerator system. In addition, an improved superconducting device, an improved quantum processor (e.g., an improved superconducting quantum processor), and / or an improved quantum computing system can be provided.

[0023] Figure 1A block diagram of an exemplary, non-limiting system 100 for providing an improved dilution refrigerator for a superconducting quantum processor according to one or more embodiments described herein is shown. For example, according to one or more embodiments described herein, the system 100 can use a low-frequency microwave signal within a dilution refrigerator to provide a novel measurement scheme for superconducting qubits. In one embodiment, the system 100 can be a quantum computing system. In another embodiment, the system 100 can additionally or alternatively be a cryogenic microwave system. In various embodiments, the system 100 can be associated with technologies such as, but not limited to, quantum computing technology, superconducting technology, quantum hardware technology, quantum computer technology, quantum circuit technology, quantum processor technology, cryogenic microwave technology, dilution refrigerator technology, quantum amplifier technology, superconducting qubit technology, microwave device technology, quantum information processing technology, artificial intelligence technology, machine learning technology, and / or other technologies. The system 100 can utilize hardware and / or software to solve problems that are highly technical, non-abstract, and cannot be performed by humans as a group of minds. In addition, some of the processes performed may be performed by one or more special computers (e.g., one or more special circuits, one or more special hardware, etc.) for performing defined processes, and / or require processes related to quantum computing and / or dilution refrigerator systems. The system 100 and / or components of the system may be used to solve new problems that arise through advances in the above-mentioned technologies, such as quantum computing technology, superconducting technology, quantum hardware technology, quantum computer technology, quantum circuit technology, quantum processor technology, dilution refrigerator technology, cryogenic microwave technology, quantum amplifier technology, superconducting qubit technology, microwave device technology, quantum information processing technology, artificial intelligence technology, machine learning technology, etc. One or more embodiments of the system 100 may provide technical improvements to quantum computing systems, superconducting systems, quantum hardware systems, quantum computer systems, quantum circuit systems, quantum processor systems, dilution refrigerator systems, cryogenic microwave systems, quantum amplifier systems, superconducting qubit systems, microwave device systems, quantum information processing systems, artificial intelligence systems, machine learning systems, and / or other technical systems. One or more embodiments of the system 100 may also provide technical improvements to dilution refrigerators by reducing the heat load in the dilution refrigerator and / or reducing the power consumption of the dilution refrigerator. Additionally or alternatively, one or more embodiments of system 100 may also provide technical improvements to quantum processors by improving the performance of quantum processors and / or improving the accuracy of quantum processors.

[0024] exist Figure 1In the illustrated embodiment, the system 100 may include a dilution refrigerator system 102, a quantum processor 104, and / or a classical computing system 106. The dilution refrigerator system 102 may be a dilution refrigerator for cooling the quantum processor 104. For example, the dilution refrigerator system 102 may be a dilution refrigerator for cooling the quantum processor 104 to a millikelvin temperature. In one embodiment, the dilution refrigerator system 102 may house the quantum processor 104. In another embodiment, the quantum processor 104 may be mounted to the dilution refrigerator system 102. In one embodiment, the quantum processor 104 may be mounted to a base stage of the dilution refrigerator system 102. The base stage may be, for example, one of the coldest parts of the dilution refrigerator system 102. The quantum processor 104 may be a device configured to manipulate quantum states for quantum computing (e.g., a quantum computer, a quantum circuit, etc.). In one embodiment, the quantum processor 104 may be a superconducting quantum processor. In one aspect, the quantum processor 104 may be a machine that performs a set of calculations based on the principles of quantum physics. For example, the quantum processor 104 may use qubits to encode and / or process information. In one embodiment, quantum processor 104 may be a hardware quantum processor (e.g., a hardware superconducting quantum processor) that may use qubits to encode and / or process information. For example, quantum processor 104 may be a hardware quantum processor that executes a set of instruction threads associated with qubits. In a non-limiting embodiment, quantum processor 104 may be a qubit-resonator. Classical computing system 106 may perform classical computing using bits (e.g., "0" value bits and "1" value bits) to store and / or process information. In one aspect, classical computing system 106 may be implemented at near room temperature (e.g., about 273K). Classical computing system 106 may additionally or alternatively manage the storage of data (e.g., bits). In addition, classical computing system 106 may include one or more electronic devices that operate at approximately room temperature.

[0025] In one embodiment, the classical computing system 106 may provide a microwave signal 108 to the dilution refrigerator system 102. The microwave signal 108 may be a radio frequency signal associated with an oscillating change in voltage and / or current. In addition, the microwave signal 108 may include one or more microwave signals. The microwave signal 108 may be used to control the quantum processor 104. Additionally or alternatively, the microwave signal 108 may be used to measure quantum information associated with the quantum processor 104. In one aspect, the microwave signal 108 may be a high frequency microwave signal in a frequency range between, for example, 4 GHz and 10 GHz. In one embodiment, the microwave signal 108 may be a qubit readout signal. For example, the microwave signal 108 may carry qubit information, such as qubit readout information.

[0026] The dilution refrigerator system 102 may modify the microwave signal 108 to generate a modified frequency microwave signal 109 for transmission within the dilution refrigerator system 102. For example, the modified frequency microwave signal 109 may be a modified version of the microwave signal 108 having a reduced frequency. In another example, the modified frequency microwave signal 109 may be a modified version of the microwave signal 108 having an increased frequency. In one embodiment, the modified frequency microwave signal 109 may be a low frequency microwave signal in a frequency range, for example, between 0.5 GHz and 2 GHz. For example, the modified frequency microwave signal 109 may include a frequency lower than a qubit frequency associated with the quantum processor 104. Additionally or alternatively, the modified frequency microwave signal 109 may include a frequency lower than a readout resonator frequency associated with the quantum processor 104. In an embodiment, the dilution refrigerator system 102 may perform a down-conversion process associated with the microwave signal 108 to generate the modified frequency microwave signal 109. The down-conversion process performed by the dilution refrigerator system 102 may be lossless and coherent. In addition, in some embodiments, the dilution refrigerator system 102 can use a set of Josephson mixers to down-convert the microwave signal 108 and generate a microwave signal 109 of modified frequency. The set of Josephson mixers can be, for example, dissipative three-wave Josephson mixers. In one implementation, in an embodiment where the microwave signal 108 is a low-frequency signal, the set of Josephson mixers can be used for up-conversion. For example, in one embodiment, the microwave signal 108 can be synthesized using one or more electronic devices (e.g., one or more electronic devices at room temperature) within the classical computing system 106. In an alternative embodiment, one or more RSFQ circuits (e.g., one or more electronic devices at the 4K level) within the dilution refrigerator system 102 can synthesize the microwave signal 108 into a low-frequency signal. In another embodiment, the microwave signal 108 can be synthesized into a high-frequency signal using one or more electronic devices (e.g., one or more electronic devices at room temperature) within the classical computing system 106. Alternatively, one or more RSFQ circuits (e.g., one or more electronic devices at the 4K level) within the dilution refrigerator system 102 can synthesize the microwave signal 108 into a high-frequency signal. In yet another embodiment, the dilution refrigerator system 102 can reduce and increase the frequency of the microwave signal 108 to provide a modified frequency microwave signal 109. For example, the dilution refrigerator system 102 can reduce the frequency of the microwave signal 108 to generate a reduced frequency version of the microwave signal 108. The dilution refrigerator system 102 can also increase the frequency of the reduced frequency version of the microwave signal 108 to a specific frequency that is lower than the original frequency of the microwave signal 108. In certain embodiments, the frequency of the microwave signal 108 can be up-converted to a readout frequency of a readout resonator associated with the quantum processor 104.In one aspect, the frequency-modified microwave signal 109 can be employed to provide a qubit measurement (e.g., a qubit measurement associated with the quantum processor 104) to the classical computing system 106. In another embodiment, the dilution refrigerator system 102 can convert the frequency-modified microwave signal 110 into a digital signal 112. The digital signal 112 can include the qubit measurement associated with the quantum processor 104. For example, the digital signal 112 can encode the qubit measurement associated with the quantum processor 104 as a sequence of binary values. In addition, the dilution refrigerator system 102 can provide the digital signal 112 to the classical computing system 106. In this way, the classical computing system 106 can perform classical signal processing of the digital signal 112 to obtain the qubit measurement associated with the quantum processor 104.

[0027] It should be understood that the system 100 can provide various advantages compared to conventional dilution refrigerator systems. For example, by using the system 100, the hardware overhead of the dilution refrigerator system associated with the quantum processor can be reduced. The reduced hardware overhead can also promote the scalability of the dilution refrigerator system. In addition, the heat load and / or mass load within the dilution refrigerator system can be reduced. The power consumption of the dilution refrigerator system associated with the quantum processor can also be reduced. In addition, by using the system 100, the performance and / or accuracy of the quantum processor associated with the dilution refrigerator system can be improved. In one example, the performance and / or accuracy of the quantum processor 104 can be improved by using a microwave signal 109 that modifies the frequency (e.g., a microwave signal that reduces the frequency). In another embodiment, the dilution refrigerator system 102 can reduce and increase the frequency of the microwave signal 108 within the dilution refrigerator system 102 to improve the coherence of the quantum processor 104 and / or reduce the hardware overhead of the quantum processor 104.

[0028] Figure 2 A block diagram of an exemplary non-limiting system 200 according to one or more embodiments described herein is shown. For the sake of brevity, repeated descriptions of similar elements employed in other embodiments described herein are omitted.

[0029] System 200 may include a dilution refrigerator system 102, a quantum processor 104, and / or a classical computing system 106. Figure 2In the illustrated embodiment, the dilution refrigerator system 102 may include a directional coupler 202, a Josephson-based isolator 204, a Josephson directional amplifier 206, a bandpass filter 208, a Josephson-based mixer 209, and / or a fast single flux quantum (RSFQ) analog-to-digital converter (ADC) 210. In an embodiment, the directional coupler 202, the Josephson-based isolator 204, the Josephson directional amplifier 206, the bandpass filter 208, and / or the Josephson-based mixer 209 may be mounted on a 10 mK stage of the dilution refrigerator system 102. Additionally or alternatively, the RSFQ ADC 210 may be mounted on a 4K stage of the dilution refrigerator system 102. The microwave signal 108 generated by the classical computing system 106 may be provided to the dilution refrigerator system 102 via an input transmission line for the dilution refrigerator system 102. In certain embodiments, the input transmission line of the dilution refrigerator system 102 may include one or more attenuators and / or one or more filters (e.g., one or more low pass filters) to attenuate and / or filter the microwave signal 108. In one embodiment, the microwave signal 108 may include a frequency corresponding to a qubit resonant frequency and / or a readout resonant frequency associated with the quantum processor 104. For example, the microwave signal 108 may include a frequency corresponding to a qubit resonant frequency of a superconducting qubit of the quantum processor 104. Additionally or alternatively, the microwave signal 108 may additionally or alternatively control one or more portions of the quantum processor 104. For example, the microwave signal 108 may control one or more portions of the quantum processor 104, may control a superconducting qubit of the quantum processor 104. Additionally or alternatively, the microwave signal 108 may facilitate one or more quantum measurements associated with the quantum processor 104. For example, the microwave signal 108 facilitates the measurement of qubit information associated with the quantum processor 104. In one example, the qubit information may include information about a qubit state (eg, an excited state, a ground state, or a superposition state) of a superconducting qubit of quantum processor 104 .

[0030] The microwave signal 108 may be received by a directional coupler 202 of the dilution refrigerator system 102. The directional coupler 202 may be a circuit that facilitates connection between the classical computing system 106, the quantum processor 104, and / or the Josephson-based isolator 204. In one aspect, the microwave signal 108 may be received by a first port of the directional coupler 202. A portion of the microwave signal 108 may be dissipated via a cold load that is coupled to the directional coupler 202 via a second port of the directional coupler 202. The cold load may be, for example, a 50 ohm load. Additionally, the remainder of the microwave signal 108 may be provided to the quantum processor 104 via a third port of the directional coupler 202. For example, the remainder of the microwave signal 108 may be provided to the quantum processor 104 via the third port. Additionally, a remaining portion of microwave signal 108 may be reflected off quantum processor 104 (e.g., off a qubit resonator of quantum processor 104) to provide a readout output signal 212 associated with qubit information (e.g., qubit measurement) associated with quantum processor 104. In one embodiment, microwave signal 108 may be reflected off quantum processor 104 via circuit quantum electrodynamics (cQED). For example, superconducting qubits of quantum processor 104 may be dispersedly coupled to a qubit resonator of quantum processor 104. Additionally, a qubit state may be determined based on a measured phase shift of microwave signal 108 applied to quantum processor 104. As such, readout output signal 212 provided by quantum processor 104 may include qubit information, such as qubit measurement, qubit state, and / or other qubit information.

[0031] The Josephson-based isolator 204, the Josephson directional amplifier 206, and / or the bandpass filter 208 may further process a readout output signal 212 (e.g., a readout output signal 212 associated with the microwave signal 108) provided by the quantum processor 104. In one aspect, the readout output signal 212 may be transmitted to the Josephson-based isolator 204 via a fourth port of the directional coupler 202. The Josephson-based isolator 204 may allow the readout output signal 212 to be transmitted without attenuation within the dilution refrigerator system 102. The Josephson-based isolator 204 may also allow the readout output signal 212 to be transmitted in a single direction toward the Josephson directional amplifier 206. In an embodiment, the Josephson-based isolator 204 may include two active Josephson mixers coupled via a beam splitter. The two active Josephson mixers of the Josephson-based isolator 204 may be driven, for example, via a microwave pump source signal. In another embodiment, the Josephson-based isolator 204 can limit the noise provided to the quantum processor 104 (e.g., noise from the output chain within the dilution refrigerator system 102). The Josephson directional amplifier 206 can amplify the readout output signal 212 of the dilution refrigerator system. The Josephson directional amplifier 206 can be a quantum confinement amplifier or a near-quantum confinement amplifier. In an embodiment, the Josephson directional amplifier 206 can include two Josephson parameter converters coupled together to facilitate amplification of the readout output signal 212. In certain embodiments, the readout output signal 212 can be additionally filtered by a bandpass filter 208 centered on a specific frequency. For example, the bandpass filter 208 can allow a specific frequency band associated with the readout output signal 212 to pass through the Josephson-based mixer 209. In one aspect, the bandpass filter 208 transmits the readout output signal 212 with minimal loss and can block DC signals and / or microwave signals below a threshold frequency. The Josephson-based mixer 209 can convert the readout output signal 212 into a microwave signal 110 of reduced frequency. The reduced frequency microwave signal 110 may include a frequency lower than the frequency of the readout output signal 212 and the frequency of the microwave signal 108. For example, the reduced frequency microwave signal 110 may include a frequency lower than the frequency of the superconducting qubits of the quantum processor 104 and the frequency of the qubit resonator of the quantum processor 104. In an embodiment, the Josephson-based mixer 209 may include a set of Josephson ring modulators coupled to one or more lumped element resonators and / or one or more surface acoustic wave resonators to facilitate down-converting the readout output signal 212 associated with the microwave signal 108 to the reduced frequency microwave signal 110.Thus, the reduced frequency microwave signal 110 may be a down-converted readout output signal (e.g., a down-converted version of the readout output signal 212), and in one embodiment, the reduced frequency microwave signal 110 generated by the Josephson-based mixer 209 may be filtered by a low-pass filter. For example, an output line between the 10mK stage of the dilution refrigerator system 102 and the 4K stage of the dilution refrigerator system 102 may include a low-pass filter between the Josephson-based mixer 209 and the RSFQ ADC 210. The low-pass filter may suppress high-frequency signals and / or noise above a cutoff frequency of the low-pass filter. For example, the low-pass filter may pass the reduced frequency microwave signal 110 with minimal loss for processing by the RSFQ ADC 210. In addition, the low-pass filter may suppress high-frequency noise associated with an output chain within the dilution refrigerator system 102. In addition, the RSFQ ADC 210 may generate a digital signal 112. For example, the RSFQ ADC 210 may sample and / or digitize the reduced frequency microwave signal 110 to generate the digital signal 112. In one embodiment, the RSFQ ADC 210 may digitize the reduced frequency microwave signal 110 based on a superconducting device to generate the digital signal 112. In this way, the digital signal 112 may include an encoded version of the qubit information included in the readout output signal 212, wherein the qubit information included in the digital signal 112 is encoded using a sequence of binary bits. In one embodiment, the RSFQ ADC 210 may employ a single flux quantum voltage pulse generated by a Josephson junction to convert the reduced frequency microwave signal 110 into the digital signal 112. The digital signal 112 generated by the RSFQ ADC 210 may be provided to the classical computing system 106 via an output transmission line for the dilution refrigerator system 102. In certain embodiments, the RSFQ ADC 210 may be an energy efficient RSFQ (ERSFQ) ADC or an energy efficient single flux quantum (eSFQ) ADC. In certain embodiments, the RSFQ ADC 210 and / or a low pass filter that filters the frequency reduced microwave signal 110 may be located on an output transmission line of the dilution refrigerator system 102 .

[0032] It should be appreciated that the system 200 may provide various advantages over conventional dilution refrigerator systems. For example, by employing the system 200, the hardware overhead of a dilution refrigerator system associated with a quantum processor may be reduced. The reduced hardware overhead may also facilitate the scalability of the dilution refrigerator system. Additionally, the heat load and / or mass load within the dilution refrigerator system may be reduced. The power consumption of the dilution refrigerator system associated with the quantum processor may also be reduced. Furthermore, by employing the system 200, the performance and / or accuracy of a quantum processor associated with the dilution refrigerator system may be improved.

[0033] Figure 3 A block diagram of an exemplary non-limiting system 300 according to one or more embodiments described herein is shown. For the sake of brevity, repeated descriptions of similar elements employed in other embodiments described herein are omitted.

[0034] System 300 may include refrigerator system 102', quantum processor 104, and / or classical computing system 106. Dilution refrigerator system 102' may be an alternative embodiment of dilution refrigerator system 102. Figure 3 In the illustrated embodiment, the dilution refrigerator system 102' may include a directional coupler 202, a Josephson-based isolator 204, a bandpass filter 208, a Josephson-based mixer 209, a direct current superconducting quantum interference device (DC-SQUID) amplifier 302, and / or an RSFQ ADC 210. In an embodiment, the directional coupler 202, the Josephson-based isolator 204, the bandpass filter 208, the Josephson-based mixer 209, and / or the DC-SQUID amplifier 302 may be mounted on a 10mK stage of the dilution refrigerator system 102'. Additionally or alternatively, the RSFQ ADC 210 may be mounted on a 4K stage of the dilution refrigerator system 102'. The microwave signal 108 generated by the classical computing system 106 may be provided to the dilution refrigerator system 102' via an input transmission line for the dilution refrigerator system 102'. In certain embodiments, the input transmission line for the dilution refrigerator system 102' may include one or more attenuators and / or one or more filters (e.g., one or more low pass filters) to attenuate and / or filter the microwave signal 108. In one embodiment, the microwave signal 108 may include a frequency corresponding to a qubit resonant frequency and / or a readout resonant frequency associated with the quantum processor 104. For example, the microwave signal 108 may include a frequency corresponding to a qubit resonant frequency of a superconducting qubit of the quantum processor 104. Additionally or alternatively, the microwave signal 108 may additionally or alternatively control one or more portions of the quantum processor 104. For example, the microwave signal 108 may control one or more portions of the quantum processor 104, may control a superconducting qubit of the quantum processor 104. Additionally or alternatively, the microwave signal 108 may facilitate one or more quantum measurements associated with the quantum processor 104. For example, the microwave signal 108 may facilitate the measurement of qubit information associated with the quantum processor 104. In one embodiment, the qubit information may include information about the qubit state (eg, excited state, ground state, or superposition state) of a superconducting qubit of quantum processor 104 .

[0035] The microwave signal 108 may be received by a directional coupler 202 of the dilution refrigerator system 102'. The directional coupler 202 may be a circuit that facilitates connection between the classical computing system 106, the quantum processor 104, and / or the Josephson-based isolator 204. In one aspect, the microwave signal 108 may be received by a first port of the directional coupler 202. A portion of the microwave signal 108 may be dissipated via a cold load that is coupled to the directional coupler 202 via a second port of the directional coupler 202. The cold load may be, for example, a 50 ohm load. Additionally, the remainder of the microwave signal 108 may be provided to the quantum processor 104 via a third port of the directional coupler 202. For example, the remainder of the microwave signal 108 may be provided to the quantum processor 104 via the third port. Additionally, a remaining portion of microwave signal 108 may be reflected away from quantum processor 104 (e.g., away from a qubit resonator of quantum processor 104) to provide a readout output signal 212 associated with qubit information (e.g., qubit measurement) associated with quantum processor 104. In one embodiment, microwave signal 108 may be reflected away from quantum processor 104 via cQED. For example, superconducting qubits of quantum processor 104 may be dispersedly coupled to a qubit resonator of quantum processor 104. Additionally, a qubit state may be determined based on a measured phase shift of microwave signal 108 applied to quantum processor 104. As such, readout output signal 212 provided by quantum processor 104 may include qubit information, such as qubit measurement, qubit state, and / or other qubit information.

[0036] The Josephson-based isolator 204 and / or the bandpass filter 208 may further process the readout output signal 212 (e.g., the readout output signal 212 associated with the microwave signal 108) provided by the quantum processor 104. In one aspect, the readout output signal 212 may be transmitted to the Josephson-based isolator 204 via the fourth port of the directional coupler 202. The Josephson-based isolator 204 may allow the readout output signal 212 to be transmitted without attenuation within the dilution refrigerator system 102'. The Josephson-based isolator 204 may also allow the readout output signal 212 to be transmitted in a single direction toward the bandpass filter 208. In an embodiment, the Josephson-based isolator 204 may include two active Josephson mixers coupled via a beam splitter. The two active Josephson mixers of the Josephson-based isolator 204 may be driven, for example, via a microwave pump source signal. In certain embodiments, the readout output signal 212 may be additionally filtered by the bandpass filter 208 centered at a specific frequency. For example, the bandpass filter 208 may allow a specific frequency band associated with the readout output signal 212 to pass through the Josephson-based mixer 209. In one aspect, the bandpass filter 208 may transmit the readout output signal 212 with minimal loss and may block DC signals and / or microwave signals below a threshold frequency. The Josephson-based mixer 209 may convert the readout output signal 212 into a reduced frequency microwave signal 110. The reduced frequency microwave signal 110 may include a frequency lower than the readout output signal 212 and the frequency of the microwave signal 108. For example, the reduced frequency microwave signal 110 may include a frequency that is lower than the frequency of the superconducting qubits of the quantum processor 104 and the frequency of the qubit resonator of the quantum processor 104. In an embodiment, the Josephson-based mixer 209 may include a set of Josephson ring modulators coupled to one or more lumped element resonators and / or one or more surface acoustic wave resonators to facilitate down-converting the readout output signal 212 associated with the microwave signal 108 into the reduced frequency microwave signal 110. Thus, the reduced frequency microwave signal 110 may be a down-converted readout output signal (e.g., a down-converted version of the readout output signal 212), and the DC-SQUID amplifier 302 may amplify the reduced frequency microwave signal 110. The DC-SQUID amplifier 302 may be a quantum confinement amplifier or a near quantum confinement amplifier. In one embodiment, the DC-SQUID amplifier 302 may include two Josephson junctions connected in parallel in a superconducting loop that is coupled to an on-chip microwave circuit to facilitate amplification of the reduced frequency microwave signal 110. In one embodiment, the amplified version of the reduced frequency microwave signal 110 generated by the DC-SQUID amplifier 302 may be filtered by a low pass filter.For example, an output line between the 10mK stage of the dilution refrigerator system 102 and the 4K stage of the dilution refrigerator system 102 may include a low-pass filter between the DC-SQUID amplifier 302 and the RSFQ ADC 210. The low-pass filter may suppress high-frequency signals and / or noise above the cutoff frequency of the low-pass filter. In addition, the RSFQ ADC 210 may generate a digital signal 112 based on an amplified version of the microwave signal 110 at a reduced frequency. For example, the RSFQ ADC 210 may sample and / or digitize the amplified version of the microwave signal 110 at a reduced frequency to generate the digital signal 112. In this way, the digital signal 112 may include an encoded version of the qubit information included in the readout output signal 212, wherein the qubit information included in the digital signal 112 is encoded using a binary bit sequence. In one embodiment, the RSFQ ADC 210 may employ a single flux quantum voltage pulse generated by a Josephson junction to convert the amplified version of the microwave signal 110 at a reduced frequency into the digital signal 112. The digital signal 112 generated by the RSFQ ADC 210 may be provided to the classical computing system 106 via an output transmission line for the dilution refrigerator system 102'. In some embodiments, the RSFQ ADC 210 may be an ERSFQ ADC or an eSFQ ADC. In some embodiments, the RSFQ ADC 210 and / or a low pass filter for filtering the reduced frequency microwave signal 110 may be located on the output transmission line of the dilution refrigerator system 102'.

[0037] It should be appreciated that system 300 may provide various advantages over conventional dilution refrigerator systems. For example, by employing system 300, the hardware overhead of a dilution refrigerator system associated with a quantum processor may be reduced. The reduced hardware overhead may also facilitate scalability of the dilution refrigerator system. Additionally, heat loads and / or mass loads within the dilution refrigerator system may be reduced. Power consumption of a dilution refrigerator system associated with a quantum processor may also be reduced. Furthermore, by employing system 300, the performance and / or accuracy of a quantum processor associated with a dilution refrigerator system may be improved.

[0038] Figure 4 A block diagram of an exemplary non-limiting system 400 according to one or more embodiments described herein is shown. For the sake of brevity, repeated descriptions of similar elements employed in other embodiments described herein are omitted.

[0039] The system 400 may include a dilution refrigerator system 102, a quantum processor 104, a classical computing system 106, RSFQ logic 402, and / or an RSFQ digital-to-analog converter (DAC) 404. The dilution refrigerator system 102 may include a directional coupler 202, a Josephson-based isolator 204, a Josephson directional amplifier 206, a bandpass filter 208, a Josephson-based mixer 209, and / or an RSFQ ADC 210. Figure 4 In the illustrated embodiment, the RSFQ DAC 404 generates the microwave signal 108. The microwave signal 108 generated by the RSFQ DAC 404 may be provided to the dilution refrigerator system 102 via an input transmission line for the dilution refrigerator system 102. In certain embodiments, the input transmission line of the dilution refrigerator system 102 may include one or more attenuators and / or one or more filters (e.g., one or more low pass filters) to attenuate and / or filter the microwave signal 108. The RSFQ DAC 404 and / or the RSFQ DAC 404 may be communicatively coupled to the classical computing system 106. For example, the RSFQ DAC 404 and / or the RSFQ DAC 404 may be communicatively coupled to one or more electronics of the classical computing system 106. In one embodiment, the RSFQ DAC 404 and / or the RSFQ DAC 404 may be located in a 4K stage of the dilution refrigerator system 102. The digital signal 112 may be provided to the classical computing system 106 and the RSFQ logic 402. The RSFQ logic 402 may include logic for facilitating conversion of the digital signal 112 into the microwave signal 108. For example, the RSFQ logic 402 may include logic for facilitating conversion of the digital signal 112 into a feedback version or a sequential version of the microwave signal 108. In certain embodiments, the RSFQ logic 402 may include logic for facilitating conversion of the digital signal 112 into a feedback version or a sequential version of the microwave signal 108 based on the results of the digital signal 112. Thus, in certain embodiments, the microwave signal 108 may be generated by a device within the dilution refrigerator system 102.

[0040] It should be appreciated that system 400 may provide various advantages over conventional dilution refrigerator systems. For example, by employing system 400, the hardware overhead of a dilution refrigerator system associated with a quantum processor may be reduced. The reduced hardware overhead may also facilitate the scalability of the dilution refrigerator system. Additionally, the heat load and / or mass load within the dilution refrigerator system may be reduced. The power consumption of the dilution refrigerator system associated with the quantum processor may also be reduced. Furthermore, by employing system 400, the performance and / or accuracy of a quantum processor associated with the dilution refrigerator system may be improved.

[0041] Figure 5A block diagram of an exemplary non-limiting system 500 according to one or more embodiments described herein is shown. For the sake of brevity, repeated descriptions of similar elements employed in other embodiments described herein are omitted.

[0042] System 500 may include dilution refrigerator system 102', quantum processor 104, classical computing system 106, RSFQ logic 402, and / or RSFQ DAC 404. Dilution refrigerator system 102' may include directional coupler 202, Josephson-based isolator 204, bandpass filter 208, Josephson-based mixer 209, DC-SQUID amplifier 302, and / or RSFQ ADC 210. Figure 5 In the illustrated embodiment, the RSFQ DAC 404 may generate the microwave signal 108. The microwave signal 108 generated by the RSFQ DAC 404 may be provided to the dilution refrigerator system 102' via an input transmission line for the dilution refrigerator system 102. In certain embodiments, the input transmission line for the dilution refrigerator system 102' may include one or more attenuators and / or one or more filters (e.g., one or more low pass filters) to attenuate and / or filter the microwave signal 108. The RSFQ DAC 404 and / or the RSFQ DAC 404 may be communicatively coupled to the classical computing system 106. For example, the RSFQ DAC 404 and / or the RSFQ DAC 404 may be communicatively coupled to one or more electronic devices of the classical computing system 106. In one embodiment, the RSFQ DAC 404 and / or the RSFQ DAC 404 may be located in a 4k stage of the dilution refrigerator system 102'. The digital signal 112 may be provided to the classical computing system 106 and the RSFQ logic 402. The RSFQ logic 402 may include logic for facilitating conversion of the digital signal 112 into the microwave signal 108. For example, the RSFQ logic 402 may include logic for facilitating conversion of the digital signal 112 into a feedback version or a sequential version of the microwave signal 108. In certain embodiments, the RSFQ logic 402 may include logic for facilitating conversion of the digital signal 112 into a feedback version or a sequential version of the microwave signal 108 based on the results of the digital signal 112. Thus, in certain embodiments, the microwave signal 108 may be generated by a device within the dilution refrigerator system 102'.

[0043] It should be appreciated that system 500 may provide various advantages over conventional dilution refrigerator systems. For example, by employing system 500, the hardware overhead of a dilution refrigerator system associated with a quantum processor may be reduced. The reduced hardware overhead may also facilitate scalability of the dilution refrigerator system. Additionally, heat loads and / or mass loads within the dilution refrigerator system may be reduced. Power consumption of a dilution refrigerator system associated with a quantum processor may also be reduced. Furthermore, by employing system 500, the performance and / or accuracy of a quantum processor associated with a dilution refrigerator system may be improved.

[0044] Figure 6 A block diagram of an example non-limiting system 600 is shown in accordance with one or more embodiments described herein. For the sake of brevity, repeated descriptions of similar elements employed in other embodiments described herein are omitted.

[0045] System 600 may include refrigerator system 102″, quantum processor 104, and / or classical computing system 106. Dilution refrigerator system 102″ may be an alternative embodiment of dilution refrigerator system 102. Figure 6In the illustrated embodiment, the dilution refrigerator system 102″ may include a Josephson-based mixer 602, a bandpass filter 604, a Josephson-based circulator 606, a Josephson-based directional amplifier 206, a bandpass filter 208, a Josephson-based mixer 209, and / or an RSFQADC 210. In one embodiment, the Josephson-based mixer 602, the bandpass filter 604, the Josephson-based circulator 606, the Josephson-based directional amplifier 206, the bandpass filter 208, and / or the Josephson-based mixer 209 may be mounted on a 10 mK stage of the dilution refrigerator system 102″. Additionally or alternatively, the RSFQ ADC 210 may be mounted on a 4K stage of the dilution refrigerator system 102″. The microwave signal 108 generated by the classical computing system 106 may be provided to the dilution refrigerator system 102″ via an input transmission line of the dilution refrigerator system 102″. In certain embodiments, the input transmission line of the dilution refrigerator system 102″ may include one or more attenuators and / or one or more filters (e.g., one or more low-pass filters) to attenuate and / or filter the microwave signal 108. In one embodiment, the microwave signal 108 may include a low frequency that is below a qubit resonant frequency and / or a readout resonant frequency associated with the quantum processor 104. For example, the microwave signal 108 may include a frequency that is below a qubit resonant frequency of a superconducting qubit of the quantum processor 104. Additionally or alternatively, the microwave signal 108 may include a frequency below a readout resonator of the quantum processor 104. In certain embodiments, the microwave signal 108 may additionally or alternatively control one or more portions of the quantum processor 104. For example, microwave signal 108 may control one or more portions of quantum processor 104, may control a superconducting qubit of quantum processor 104. Additionally or alternatively, microwave signal 108 may facilitate one or more quantum measurements associated with quantum processor 104. For example, microwave signal 108 may facilitate measurement of qubit information associated with quantum processor 104. In one example, qubit information may include information about a qubit state (e.g., an excited state, a ground state, or a superposition state) of a superconducting qubit of quantum processor 104. Microwave signal 108 may be received by a Josephson-based mixer 602 of dilution refrigerator system 102". Josephson-based mixer 602 may facilitate transmission and / or generation of microwave signal 108 based on a pump signal having a particular frequency. In one aspect, Josephson-based mixer 602 may upconvert microwave signal 108 into a microwave signal of increased frequency. For example, Josephson-based mixer 602 may upconvert microwave signal 108 into a readout signal 213.In an embodiment, the Josephson-based mixer 602 may include a set of Josephson ring modulators coupled to one or more lumped element resonators and / or one or more surface acoustic wave resonators to facilitate up-converting the microwave signal 108 into a microwave signal of increased frequency. Thus, the readout signal 213 may be an up-converted readout output signal. In certain embodiments, the microwave signal 108 may be additionally filtered by a bandpass filter 604 centered at a particular frequency. For example, the bandpass filter 604 may allow a particular frequency band associated with the microwave signal 108 to pass through to reach the Josephson-based circulator 606. In one aspect, the bandpass filter 604 may transmit the microwave signal 108 with minimal loss and may block DC signals and / or microwave signals below a threshold frequency.

[0046] The Josephson-based circulator 606 can be a circuit that facilitates the connection between the classical computing system 106, the quantum processor 104, and / or the Josephson directional amplifier 206. In one aspect, the Josephson-based circulator 606 can be a non-reciprocal microwave device. In one implementation, the Josephson-based circulator 606 can include three ports. In another implementation, the Josephson-based circulator 606 can include four ports. In an example, a signal entering a port of the Josephson-based circulator 606 can be routed to another port of the Josephson-based circulator 606 with low loss based on a predefined circulation direction. In one implementation, the microwave signal 108 can be received by a first port of the Josephson-based circulator 606. In addition, the quantum processor 104 can be coupled to a second port of the Josephson-based circulator 606. A portion of the microwave signal 108 may be reflected off the quantum processor 104 (e.g., off a qubit resonator of the quantum processor 104) via the second port to provide a readout output signal associated with qubit information (e.g., qubit measurement) associated with the quantum processor 104. The readout output signal may be sent via the third port of the Josephson-based circulator 606. In certain embodiments, a cold load may be coupled to the Josephson-based circulator 606 via the fourth port of the Josephson-based circulator 606. The cold load may be, for example, a 50 ohm load. In one embodiment, the microwave signal 108 may be reflected off the quantum processor 104 via the cQED. For example, the superconducting qubits of the quantum processor 104 may be dispersedly coupled to the qubit resonator of the quantum processor 104. In addition, the qubit state may be determined based on the measured phase shift of the microwave signal 108 applied to the quantum processor 104. In this way, the readout output signal provided by the quantum processor 104 may include qubit information, such as qubit measurement, qubit state, and / or other qubit information. In one aspect, the Josephson-based circulator 606 can prevent the Josephson directional amplifier 206 from excessively reacting to the qubit information associated with the readout output signal. In one embodiment, the Josephson-based circulator 606 can be implemented without magnetic materials and / or strong magnetic fields. In another embodiment, the Josephson-based circulator 606 can include a set of Josephson parameter converters.

[0047] The Josephson directional amplifier 206 and / or the bandpass filter 208 may further process the readout output signal (e.g., the readout output signal associated with the microwave signal 108) provided by the quantum processor 104. In one aspect, the readout output signal may be transmitted to the Josephson directional amplifier 206. The Josephson directional amplifier 206 may amplify the readout output signal. The Josephson directional amplifier 206 may be a quantum confinement amplifier or a near-quantum confinement amplifier. In an embodiment, the Josephson directional amplifier 206 may include two Josephson parameter converters coupled together to facilitate amplification of the readout output signal. In certain embodiments, the readout output signal may be additionally filtered by a bandpass filter 208 centered at a specific frequency. For example, the bandpass filter 208 may allow a specific frequency band associated with the readout output signal to pass through to reach the Josephson-based mixer 209. In one aspect, the bandpass filter 208 may transmit the readout output signal with minimal loss and may block DC signals and / or microwave signals below a threshold frequency. The Josephson-based mixer 209 may convert the readout output signal into a microwave signal 110 of reduced frequency. The reduced frequency microwave signal 110 may include a frequency lower than the frequency of the readout output signal and the frequency of the microwave signal 108. For example, the reduced frequency microwave signal 110 may include a frequency that is lower than the frequency of the superconducting qubits of the quantum processor 104 and the frequency of the qubit resonator of the quantum processor 104. In an embodiment, the Josephson-based mixer 209 may include a set of Josephson ring modulators coupled to one or more lumped element resonators and / or one or more surface acoustic wave resonators to facilitate down-converting the readout output signal associated with the microwave signal 108 to the reduced frequency microwave signal 110. Thus, the reduced frequency microwave signal 110 may be a down-converted readout output signal (e.g., a down-converted version of the readout output signal). In an embodiment, the reduced frequency microwave signal 110 generated by the Josephson-based mixer 209 may be filtered by a low pass filter. For example, an output line between a 10 mK stage of the dilution refrigerator system 102 and a 4 K stage of the dilution refrigerator system 102 may include a low pass filter between the Josephson-based mixer 209 and the RSFQ ADC 210. The low pass filter may suppress high frequency signals and / or noise above a cutoff frequency of the low pass filter. In addition, the RSFQ ADC 210 may generate a digital signal 112. For example, the RSFQ ADC 210 may sample and / or digitize the reduced frequency microwave signal 110 to generate the digital signal 112. In this way, the digital signal 112 may include an encoded version of the qubit information included in the readout output signal, wherein the qubit information included in the digital signal 112 is encoded using a binary bit sequence.In one embodiment, the RSFQ ADC 210 may employ a single flux quantum voltage pulse generated by a Josephson junction to convert the reduced frequency microwave signal 110 into a digital signal 112. The digital signal 112 generated by the RSFQ ADC 210 may be provided to the classical computing system 106 via an output transmission line for the dilution refrigerator system 102″. In some embodiments, the RSFQ ADC 210 may be an ERSFQ ADC or an eSFQ ADC. In some embodiments, the RSFQ ADC 210 and / or a low pass filter for filtering the reduced frequency microwave signal 110 may be located on the output transmission line of the dilution refrigerator system 102″.

[0048] It should be appreciated that system 600 may provide various advantages over conventional dilution refrigerator systems. For example, by employing system 600, the hardware overhead of a dilution refrigerator system associated with a quantum processor may be reduced. The reduced hardware overhead may also facilitate the scalability of the dilution refrigerator system. Additionally, the heat load and / or mass load within the dilution refrigerator system may be reduced. The power consumption of the dilution refrigerator system associated with the quantum processor may also be reduced. Furthermore, by employing system 600, the performance and / or accuracy of a quantum processor associated with the dilution refrigerator system may be improved.

[0049] Figure 7 A block diagram of an exemplary non-limiting system 700 according to one or more embodiments described herein is shown. For the sake of brevity, repeated descriptions of similar elements employed in other embodiments described herein are omitted.

[0050] System 700 may include a dilution refrigerator system 102'', a quantum processor 104, and / or a classical computing system 106. Dilution refrigerator system 102'' may be an alternative embodiment of dilution refrigerator system 102'. Figure 7In the illustrated embodiment, the dilution refrigerator system 102'" may include a Josephson-based mixer 602, a bandpass filter 604, a Josephson-based circulator 606, a bandpass filter 208, a Josephson-based mixer 209, a DC-SQUID amplifier, and / or an RSFQ ADC 210. In one embodiment, the Josephson-based mixer 602, the bandpass filter 604, the Josephson-based circulator 606, the bandpass filter 208, the Josephson-based mixer 209, and / or the DC-SQUID amplifier may be mounted on a 10 mK stage of the dilution refrigerator system 102'". Additionally or alternatively, the RSFQ ADC 210 may be mounted on a 4K stage of the dilution refrigerator system 102'". The microwave signal 108 generated by the classical computing system 106 may be provided to the dilution refrigerator system 102'" via an input transmission line for the dilution refrigerator system 102'". In certain embodiments, the input transmission line for the dilution refrigerator system 102'" may include one or more attenuators and / or one or more filters (e.g., one or more low-pass filters) to attenuate and / or filter the microwave signal 108. In one embodiment, the microwave signal 108 may include a frequency corresponding to a qubit resonant frequency and / or a readout resonant frequency associated with the quantum processor 104. For example, the microwave signal 108 may include a frequency corresponding to a qubit resonant frequency of a superconducting qubit of the quantum processor 104. Additionally or alternatively, the microwave signal 108 may include a frequency corresponding to a readout resonator of the quantum processor 104. In certain embodiments, the microwave signal 108 may additionally or alternatively control one or more portions of the quantum processor 104. For example, microwave signal 108 may control one or more portions of quantum processor 104, may control a superconducting qubit of quantum processor 104. Additionally or alternatively, microwave signal 108 may facilitate one or more quantum measurements associated with quantum processor 104. For example, microwave signal 108 may facilitate measurement of qubit information associated with quantum processor 104. In one embodiment, qubit information may include information about a qubit state (e.g., an excited state, a ground state, or a superposition state) of a superconducting qubit of quantum processor 104. Microwave signal 108 may be received by a Josephson-based mixer 602 of dilution refrigerator system 102″′. Josephson-based mixer 602 may facilitate transmission and / or generation of microwave signal 108 based on a pump signal having a particular frequency. In one aspect, Josephson-based mixer 602 may upconvert microwave signal 108 into a microwave signal of increased frequency. For example, Josephson-based mixer 602 may upconvert microwave signal 108 into a readout signal 213.In an embodiment, the Josephson-based mixer 602 may include a set of Josephson ring modulators coupled to one or more lumped element resonators and / or one or more surface acoustic wave resonators to facilitate up-converting the microwave signal 108 into a microwave signal of increased frequency. Thus, the readout signal 213 may be an up-converted readout output signal. In certain embodiments, the microwave signal 108 may be additionally filtered by a bandpass filter 604 centered at a particular frequency. For example, the bandpass filter 604 may allow a particular frequency band associated with the microwave signal 108 to pass through to reach the Josephson-based circulator 606. In one aspect, the bandpass filter 604 may transmit the microwave signal 108 with minimal loss and may block DC signals and / or microwave signals below a threshold frequency.

[0051] The Josephson-based circulator 606 can be a circuit that facilitates the connection between the classical computing system 106, the quantum processor 104, and / or the Josephson directional amplifier 206. In one aspect, the Josephson-based circulator 606 can be a non-reciprocal microwave device. In one implementation, the Josephson-based circulator 606 can include three ports. In another implementation, the Josephson-based circulator 606 can include four ports. In an example, a signal entering a port of the Josephson-based circulator 606 can be routed to another port of the Josephson-based circulator 606 with low loss based on a predefined circulation direction. In one implementation, the microwave signal 108 can be received by a first port of the Josephson-based circulator 606. In addition, the quantum processor 104 can be connected to a second port of the Josephson-based circulator 606. A portion of the microwave signal 108 may be reflected off the quantum processor 104 (e.g., off a qubit resonator of the quantum processor 104) via the second port to provide a readout output signal associated with qubit information (e.g., qubit measurement) associated with the quantum processor 104. The readout output signal may be transmitted via the third port of the Josephson-based circulator 606. In certain embodiments, a cold load may be coupled to the Josephson-based circulator 606 via the fourth port of the Josephson-based circulator 606. The cold load may be, for example, a 50 ohm load. In one embodiment, the microwave signal 108 may be reflected off the quantum processor 104 via the cQED. For example, the superconducting qubits of the quantum processor 104 may be dispersedly coupled to the qubit resonator of the quantum processor 104. In addition, the qubit state may be determined based on the measured phase shift of the microwave signal 108 applied to the quantum processor 104. In this way, the readout output signal provided by the quantum processor 104 may include qubit information, such as qubit measurement, qubit state, and / or other qubit information. In one aspect, the Josephson-based circulator 606 can prevent excessive reaction of the DC-SQUID amplifier 302 to the qubit information associated with the readout output signal. In one embodiment, the Josephson-based circulator 606 can be implemented without magnetic materials and / or strong magnetic fields. In another embodiment, the Josephson-based circulator 606 can include a set of Josephson parameter converters.

[0052] The bandpass filter 208 can further process the readout output signal provided by the quantum processor 104 (e.g., the readout output signal associated with the microwave signal 108). In one aspect, the readout output signal can be additionally filtered by the bandpass filter 208 centered at a specific frequency. For example, the bandpass filter 208 can allow a specific frequency band associated with the readout output signal to pass through the Josephson-based mixer 209. In one aspect, the bandpass filter 208 can transmit the readout output signal with minimal loss and can block DC signals and / or microwave signals below a threshold frequency. The Josephson-based mixer 209 can convert the readout output signal into a reduced frequency microwave signal 110. The reduced frequency microwave signal 110 can include a frequency lower than the frequency of the readout output signal and the frequency of the microwave signal 108. For example, the reduced frequency microwave signal 110 can include a frequency that is lower than the frequency of the superconducting qubit of the quantum processor 104 and the frequency of the qubit resonator of the quantum processor 104. In an embodiment, the Josephson-based mixer 209 may include a set of Josephson ring modulators coupled to one or more lumped element resonators and / or one or more surface acoustic wave resonators to facilitate down-converting a readout output signal associated with the microwave signal 108 to a reduced frequency microwave signal 110. Thus, the reduced frequency microwave signal 110 may be a down-converted readout output signal (e.g., a down-converted version of the readout output signal), and the DC-SQUID amplifier 302 may amplify the reduced frequency microwave signal 110. The DC-SQUID amplifier 302 may be a quantum confined amplifier or a near-quantum confined amplifier. In an embodiment, the DC-SQUID amplifier 302 may include two Josephson junctions connected in parallel in a superconducting loop to facilitate amplifying the reduced frequency microwave signal 110. In an embodiment, the amplified version of the reduced frequency microwave signal 110 generated by the DC-SQUID amplifier 302 may be filtered by a low pass filter. For example, an output line between the 10 mK stage of the dilution refrigerator system 102 and the 4 K stage of the dilution refrigerator system 102 may include a low pass filter between the DC-SQUID amplifier 302 and the RSFQ ADC 210. The low pass filter may suppress high frequency signals and / or noise above a cutoff frequency of the low pass filter. In addition, the RSFQ ADC 210 may generate a digital signal 112 based on an amplified version of the reduced frequency microwave signal 110. For example, the RSFQ ADC 210 may sample and / or digitize the amplified version of the reduced frequency microwave signal 110 to generate the digital signal 112. As such, the digital signal 112 may include an encoded version of the qubit information included in the readout output signal, wherein the qubit information included in the digital signal 112 is encoded using a binary bit sequence.In one embodiment, the RSFQ ADC 210 may employ a single flux quantum voltage pulse generated by a Josephson junction to convert an amplified version of the reduced frequency microwave signal 110 into a digital signal 112. The digital signal 112 generated by the RSFQ ADC 210 may be provided to the classical computing system 106 via an output transmission line for the dilution refrigerator system 102. In certain embodiments, the output transmission line for the dilution refrigerator system 102' may include one or more attenuators and / or one or more filters to attenuate and / or filter the digital signal 112. In certain embodiments, the RSFQ ADC 210 may be an ERSFQ ADC or an eSFQ ADC.

[0053] In certain embodiments, the RSFQ ADC 210 and / or a low pass filter for filtering the frequency reduced microwave signal 110 may be located on an output transmission line of the dilution refrigerator system 102'".

[0054] It should be appreciated that system 700 may provide various advantages over conventional dilution refrigerator systems. For example, by employing system 700, the hardware overhead of a dilution refrigerator system associated with a quantum processor may be reduced. The reduced hardware overhead may also facilitate the scalability of the dilution refrigerator system. Additionally, the heat load and / or mass load within the dilution refrigerator system may be reduced. The power consumption of the dilution refrigerator system associated with the quantum processor may also be reduced. Furthermore, by employing system 700, the performance and / or accuracy of a quantum processor associated with the dilution refrigerator system may be improved.

[0055] Figure 8 A block diagram of an exemplary non-limiting system 800 according to one or more embodiments described herein is shown. For the sake of brevity, repeated descriptions of similar elements employed in other embodiments described herein are omitted.

[0056] System 800 includes a classical computing system 106. Classical computing system 106 may be communicatively coupled to dilution refrigerator system 102, dilution refrigerator system 102', dilution refrigerator system 102", or dilution refrigerator system 102'". Figure 8In the illustrated embodiment, the classical computing system 106 may include classical signal management 802 and / or one or more electronic devices 804. The classical signal management 802 may be communicatively coupled to the one or more electronic devices 804. The classical signal management 802 and / or the one or more electronic devices 804 may operate, for example, in a computing environment at room temperature (e.g., at approximately 273K). The classical signal management 802 may perform classical signal processing associated with the digital signal 112. The classical signal management 802 may additionally or alternatively perform signal analysis associated with the digital signal 112. Furthermore, the classical computing system 106 may additionally or alternatively manage storage of data (e.g., bits) associated with the digital signal 112. The one or more electronic devices 804 may generate the microwave signal 108 and / or may transmit the microwave signal 108 to the dilution refrigerator system 102, the dilution refrigerator system 102', the dilution refrigerator system 102", or the dilution refrigerator system 102'". In an embodiment, the one or more electronic devices 804 may be one or more signal generators. In some embodiments, the classical signal management 802 and the one or more electronic devices 804 may exchange one or more analog signals and / or one or more digital signals. In some embodiments, the classical signal management 802 and / or the one or more electronic devices 804 may control one or more functions associated with the RSFQ logic 402 and / or the RSFQ DAC 404. In some embodiments, the classical signal management 802 and / or the one or more electronic devices 804 may transmit one or more analog signals to the RSFQ logic 402 and / or the RSFQ DAC 404.

[0057] Fig. 9 A block diagram of an exemplary non-limiting system 900 according to one or more embodiments described herein is shown. For the sake of brevity, repeated descriptions of similar elements employed in other embodiments described herein are omitted.

[0058] System 900 includes a Josephson-based mixer 901. For example, the Josephson-based mixer 901 may correspond to the Josephson-based mixer 209. However, in another example, the Josephson-based mixer 901 may correspond to the Josephson-based mixer 602. The Josephson-based mixer 901 may include a microwave resonator 902, a surface acoustic wave resonator 904, and a Josephson ring modulator 906. The microwave resonator 902 may be a microwave resonator capable of resonating at a specific microwave frequency. The surface acoustic wave resonator 904 may be an electromechanical resonator that may resonate one or more microwave frequencies different from the microwave resonator. In one aspect, the microwave resonator 902 may include a first resonant frequency, and the surface acoustic wave resonator 904 may include a second resonant frequency. The Josephson ring modulator 906 may include a set of Josephson tunnel junctions. For example, the Josephson ring modulator 906 may include a set of Josephson junctions arranged in a Wheatstone bridge configuration. Additionally or alternatively, the Josephson ring modulator 906 may include a set of shunt junctions. In an embodiment, the pump signal 908 may be utilized to control the frequency down-conversion of the readout output signal 212 to the reduced frequency microwave signal 110 via, for example, the microwave resonator 902, the surface acoustic wave resonator 904, and the Josephson ring modulator 906. In certain embodiments, the Josephson-based mixer 901 may include a coupling capacitor 910, a coupling capacitor 912, a coupling capacitor 914, and / or a coupling capacitor 916 to facilitate one or more couplings between the microwave resonator 902, the surface acoustic wave resonator 904, and / or the Josephson ring modulator 906. The coupling capacitor 910, the coupling capacitor 912, the coupling capacitor 914, and / or the coupling capacitor 916 may additionally or alternatively facilitate processing of the readout output signal 212, the reduced frequency microwave signal 110, and / or the pump signal 908. For example, the coupling capacitor 916 may couple an external transmission line carrying the reduced frequency microwave signal 110 to the surface acoustic wave resonator 904. Coupling capacitor 910 may couple an external transmission line carrying readout output signal 212 to microwave resonator 902. For example, coupling capacitor 912 and / or coupling capacitor 914 may couple transmission line 918 carrying input and output pump drives to a Josephson ring modulator.

[0059] Fig.10A flow chart of an exemplary non-limiting method 1000 for providing an improved dilution refrigerator for a superconducting quantum processor according to one or more embodiments described herein is shown. At 1002, a microwave signal is converted into a microwave signal of reduced frequency by a dilution refrigerator system associated with a quantum processor based on a Josephson mixer circuit located within the dilution refrigerator system. At 1004, the microwave signal of reduced frequency is digitized into a digital signal including qubit information associated with the quantum processor by the dilution refrigerator system. At 1004, the digital signal is transmitted to a classical computing system by the dilution refrigerator system. In some embodiments, the method 1000 may additionally or alternatively include receiving the microwave signal from the classical computing system by the dilution refrigerator system. In some embodiments, the method 1000 may additionally or alternatively include amplifying the microwave signal by the dilution refrigerator system via a Josephson directional amplifier located within the dilution refrigerator system. In some embodiments, the method 1000 may additionally or alternatively include isolating the quantum processor from noise by the dilution refrigerator system via a Josephson-based isolator located within the dilution refrigerator system. In certain embodiments, method 1000 may additionally or alternatively include protecting, by the dilution refrigerator system, the quantum processor from noise associated with an output chain of the dilution refrigerator system using a Josephson-based isolator located within the dilution refrigerator system.

[0060] For the simplicity of explanation, subject knowledge is depicted and described as a series of actions.It is understandable and clear that the present invention is not subject to the restriction of shown action and / or action sequence, for example, action can occur in various orders and / or in parallel, and can occur together with other actions that are not presented and described herein.In addition, according to disclosed theme, not all actions shown are needed for the process of realizing theme.In addition, those skilled in the art will understand and appreciate that the subject knowledge base can be alternatively represented as a series of interrelated states via state diagram or event.

[0061] Furthermore, because the microwave signal is at least converted to a reduced frequency microwave signal, digitized to a reduced frequency microwave signal, etc., which are established by a combination of electrical and mechanical components and circuits, a human being cannot replicate or perform the processing performed by the systems and / or devices disclosed herein. For example, a human being cannot convert a microwave signal to a reduced frequency microwave signal. Furthermore, a human being cannot digitize to a reduced frequency microwave signal.

[0062] In addition, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or". That is, unless otherwise specified or clear from the context, "X employs A or B" is intended to mean any natural inclusive arrangement. That is, if X employs A; X employs B; or X employs both A and B, then "X employs A or B" is satisfied in any of the foregoing instances. In addition, unless otherwise specified or clear from the context to refer to the singular form, the articles "a" and "an" as used in this specification and the drawings should generally be interpreted as meaning "one or more". As used herein, the terms "example" and / or "exemplary" are used to indicate use as an example, instance, or illustration. For the avoidance of doubt, the subject matter disclosed herein is not limited to these examples. In addition, any aspect or design described herein as "example" and / or "exemplary" is not necessarily to be construed as being preferred or advantageous over other aspects or designs, nor is it meant to exclude equivalent exemplary structures and techniques known to those of ordinary skill in the art.

[0063] The above description includes examples of systems and computer-implemented methods. Of course, it is not possible to describe every conceivable combination of components or computer-implemented methods for the purpose of describing the present disclosure, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present disclosure are possible. In addition, to the extent the terms "including," "having," "having," and the like are used in the detailed description, claims, appendices, and drawings, these terms are intended to be inclusive in a manner similar to that in which the term "comprising" is interpreted when used as a transitional word in the claims.

[0064] The description of various embodiments has been presented for the purpose of illustration, but is not intended to be exhaustive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terms used herein are selected to best explain the principles of the embodiments, practical applications, or technical improvements existing in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A cryogenic microwave system for measuring superconducting qubits using microwave signals, comprising: A dilution refrigerator system for a quantum processor, the dilution refrigerator system converting a microwave signal associated with qubit information into a reduced frequency microwave signal based on a Josephson mixer circuit located within the dilution refrigerator system, wherein the reduced frequency microwave signal includes a frequency lower than the qubit frequency and a readout resonator frequency associated with the quantum processor.

2. The cryogenic microwave system of claim 1, wherein an input transmission line for the dilution refrigerator system comprises an attenuator and a low pass filter to attenuate and filter the microwave signal.

3. The cryogenic microwave system of claim 1 , wherein an output transmission line for the dilution refrigerator system comprises a low pass filter to reject specific frequency signals and noise, and wherein the output transmission line comprises an analog-to-digital converter and a low pass filter to digitize and filter the reduced frequency microwave signal.

4. The cryogenic microwave system of claim 1, wherein the dilution refrigerator system comprises an analog-to-digital converter that digitizes the reduced frequency microwave signal based on a superconducting device to generate a digital signal for a classical computing system.

5. The cryogenic microwave system of claim 1, wherein the reduced frequency microwave signal is employed to improve performance of the quantum processor.

6. A system comprising: A dilution refrigerator system for a quantum processor, the dilution refrigerator system reducing and increasing the frequency of a microwave signal associated with a qubit readout to provide a qubit measurement associated with the quantum processor, wherein the microwave signal is a first microwave signal, and wherein the dilution refrigerator system includes a Josephson mixer circuit that converts the first microwave signal to a second microwave signal, and wherein a first frequency associated with the first microwave signal is greater than a second frequency associated with the second microwave signal.

7. The system of claim 6, wherein the dilution refrigerator system comprises a fast single flux quantum RSFQ analog-to-digital converter (ADC) that digitizes the second microwave signal based on a superconducting device to generate a digital signal for a classical computing system.

8. The system of claim 7, wherein the dilution refrigerator system comprises a near-quantum confinement amplifier that amplifies the second microwave signal to produce an amplified version of the second microwave signal for processing by the RSFQ ADC.

9. The system of claim 7, wherein the dilution refrigerator system includes a quantum confinement amplifier that amplifies the first microwave signal to generate an amplified version of the first microwave signal for processing by the Josephson mixer circuit.

10. The system of claim 7, wherein the dilution refrigerator system includes a Josephson-based isolator including a set of Josephson mixers to limit noise provided to the quantum processor by an output chain within the dilution refrigerator system.

11. The system of claim 6, wherein the dilution refrigerator system includes a bandpass filter that filters the first microwave signal based on a frequency band to generate a filtered version of the first microwave signal for processing by the Josephson mixer circuit.

12. The system of claim 7, wherein the dilution refrigerator system includes a low pass filter that transmits the second microwave signal with minimal loss for processing by the RSFQ ADC.

13. The system of claim 6, wherein the system further comprises: A classical computing system comprising electronic equipment generating said microwave signal.

14. The system of claim 6, wherein the dilution refrigerator system reduces and increases the frequency of the microwave signal within the dilution refrigerator system to improve coherence of the quantum processor.

15. A method comprising: The microwave signal is converted into a microwave signal of reduced frequency by a dilution refrigerator system associated with the quantum processor based on a Josephson mixer circuit located within the dilution refrigerator system; digitizing, by the dilution refrigerator system, the reduced frequency microwave signal into a digital signal comprising qubit information associated with the quantum processor; and The digital signal is transmitted by the dilution refrigerator system to a classical computing system.

16. The method according to claim 15, further comprising: The microwave signal is received by the dilution refrigerator system from the classical computing system.

17. The method according to claim 15, further comprising: The microwave signal is amplified by the dilution refrigerator system via a Josephson directional amplifier located within the dilution refrigerator system.

18. The method according to claim 15, further comprising: The quantum processor is protected by the dilution refrigerator system from noise associated with an output chain of the dilution refrigerator system using a Josephson-based isolator located within the dilution refrigerator system.

19. A system comprising: a Josephson mixer circuit that converts a first microwave signal associated with quantum information generated by a quantum processor into a second microwave signal, wherein a first frequency associated with the first microwave signal is greater than a second frequency associated with the second microwave signal; and A fast single-flux quantum RSFQ analog-to-digital converter ADC is provided, wherein the fast single-flux quantum analog-to-digital converter digitizes the second microwave signal based on a superconducting device to generate a digital signal for a classical computing system.

20. The system of claim 19, further comprising: A quantum confinement amplifier amplifies the second microwave signal to generate an amplified version of the second microwave signal for processing by the RSFQADC.

21. The system of claim 19, further comprising: A quantum confinement amplifier amplifies the first microwave signal to generate an amplified version of the first microwave signal for processing by the Josephson mixer circuit.

22. A system comprising: Quantum processors; as well as A dilution refrigerator system that reduces the frequency of a first microwave signal associated with qubit readout via a Josephson mixer circuit to generate a second microwave signal, and digitizes the second microwave signal via a single-flux quantum RSFQ analog-to-digital converter ADC to generate a digital signal for a classical computing system.

23. The system of claim 22, further comprising: A near-quantum confinement amplifier amplifies the second microwave signal to generate an amplified version of the second microwave signal for processing by the RSFQ ADC.

24. The system of claim 22, further comprising: A quantum confinement amplifier amplifies the first microwave signal to generate an amplified version of the first microwave signal for processing by the Josephson mixer circuit.

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