Josephson Mixer Downconversion for Superconducting Qubit Readout
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Solution Overview
Problem
Conventional dilution refrigerator systems face challenges in reducing black-body radiation noise and electromagnetic noise, which require significant hardware overhead, introduce large heat loads, and consume substantial power, making them inefficient for superconducting quantum processors.
Innovation Solution
A novel measurement scheme using low-frequency microwave signals within a dilution refrigerator system, employing Josephson mixers for lossless downconversion, quantum-limited amplification, and RSFQ circuits to reduce noise and hardware complexity, while eliminating the need for cryogenic magnetic-based circulators and room-temperature mixers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional dilution refrigerator systems use cryogenic magnetic-based circulators and room-temperature mixers to reduce black-body radiation noise and electromagnetic noise, then noise reduction is achieved, but hardware overhead, heat load, and power consumption increase significantly
Solution Approach 1:
The patent extracts and eliminates the need for cryogenic magnetic-based circulators and room-temperature mixers from the system. By using Josephson mixers operated at cryogenic temperatures, the system removes unnecessary hardware components while maintaining noise reduction capabilities, thereby reducing hardware overhead and heat load
Solution Approach 2:
The Josephson mixer circuit serves multiple functions simultaneously: it acts as a frequency converter, a noise filter, and a signal amplifier. This multi-functionality replaces what previously required separate dedicated components for each function, reducing overall hardware complexity and overhead
2Object-affected harmful factors
If conventional dilution refrigerator systems use cryogenic magnetic-based circulators and room-temperature mixers to reduce black-body radiation noise and electromagnetic noise, then noise reduction is achieved, but heat load and power consumption increase significantly
Solution Approach 1:
The patent removes the need for power-intensive room-temperature mixers and cryogenic magnetic-based circulators by replacing them with Josephson mixer circuits that operate efficiently at cryogenic temperatures, significantly reducing overall power consumption while maintaining noise reduction performance
Solution Approach 2:
The system changes the operating temperature parameter of the mixer from room temperature to cryogenic temperatures, enabling the use of superconducting Josephson junctions that consume much less power while providing superior noise rejection and frequency conversion efficiency
3Object-affected harmful factors
If conventional dilution refrigerator systems use multiple shields and thermal isolations to reduce black-body radiation noise and electromagnetic noise, then noise reduction is achieved, but hardware overhead and complexity increase
Solution Approach 1:
The patent replaces mechanical and magnetic-based noise reduction systems (circulators, shields, thermal isolations) with a quantum-electrical system using Josephson mixers. This substitution achieves noise reduction through quantum mechanical effects rather than macroscopic mechanical structures, dramatically reducing hardware overhead and complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces hardware overhead, heat load, and power consumption, while improving the performance and accuracy of quantum processors by minimizing noise and enhancing coherence.
Implementation Method 1
converting the microwave signal into a reduced-frequency microwave signal based on a Josephson-mixer circuit
Implementation Method 2
amplifying the reduced-frequency microwave signal with a quantum-limited amplifier
Implementation Method 3
converting the amplified reduced-frequency microwave signal into a digital signal based on rapid single flux quantum (RSFQ) circuits
Data Source
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AI summary
Techniques that facilitate a measurement scheme for superconducting qubits using low-frequency microwave signals within a dilution refrigerator are 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 below a qubit frequency and a readout resonator frequency associated with the quantum processor.