Superconducting Isolator Using Josephson Three-Wave Mixing
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Solution Overview
Problem
Current cryogenic isolators for superconducting circuits are large, heavy, difficult to thermalize, and require ferrites and magnets, which are challenging to integrate and can interfere with circuit operations.
Innovation Solution
A superconducting two-port isolator is developed using nondegenerate three-wave mixing Josephson devices coupled back-to-back with a lumped-element resistor, achieving non-reciprocity through phase shifts and noiseless frequency conversion, allowing for on-chip integration without ferrites or strong magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ferrite-based isolators are used for superconducting circuits, then non-reciprocity and isolation are achieved, but the device becomes large, heavy, and difficult to thermalize
Solution Approach 1:
The patent changes the fundamental operating parameters by replacing ferrite materials with superconducting Josephson junctions operating at cryogenic temperatures. This parameter change enables non-reciprocity through quantum mechanical effects rather than magnetic hysteresis, achieving isolation without the weight and thermalization problems of ferrite-based devices
Solution Approach 2:
The patent substitutes the mechanical/magnetic system (ferrite magnets and magnetic fields) with a quantum electronic system based on Josephson junctions. The non-reciprocity is achieved through the nonlinear inductance of the Josephson junctions and three-wave mixing processes, eliminating the need for heavy magnetic components
2Reliability
If ferrite-based isolators are used for superconducting circuits, then non-reciprocity is achieved, but integration becomes challenging and magnetic fields interfere with circuit operations
Solution Approach 1:
The patent merges the isolator function directly into the superconducting circuit architecture using Josephson junctions that are already part of the quantum circuit. The isolator is formed by coupling superconducting resonators with nonlinear inductors, creating an integrated device that performs both quantum computation and signal isolation without separate magnetic components
Solution Approach 2:
The patent extracts the non-reciprocity function from the heavy ferrite magnetic materials and implements it through the intrinsic nonlinear properties of Josephson junctions. This extraction eliminates the need for external magnets and ferrite components, reducing integration complexity and eliminating magnetic field interference
3Reliability
If conventional isolators are used, then isolation is provided, but the device is large and not suitable for on-chip integration
Solution Approach 1:
The patent implements a compact isolator design where the nonlinear inductor (Josephson junction) is nested within the superconducting resonator structure. This nested configuration achieves isolation functionality in a miniaturized form factor that can be integrated on the same chip as quantum circuits, eliminating the need for large external isolator components
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
The solution provides a compact, lightweight isolator with high isolation (about 20 dB) that can be thermally well-integrated and has reversible directionality, eliminating the need for ferrites and magnets, while maintaining unity transmission in one direction and attenuation in the opposite.
Implementation Method 1
nondegenerate three-wave mixing Josephson devices
Implementation Method 2
Josephson devices
Implementation Method 3
phase shifts and noiseless frequency conversion
Implementation Method 4
lumped-element resistor connected in parallel to the gyrator
Data Source
AI summary
A technique relates to a superconducting device. A gyrator includes a first mixing device coupled to a second mixing device. A lumped-element resistor is connected in parallel to the gyrator.