Cryogenic Circulator Using Spatiotemporal Modulation Without Magnets
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Solution Overview
Problem
Existing circulators used in quantum computing are unsuitable due to magnetic interference, and existing magnet-free technologies are incompatible with low temperature superconductivity.
Innovation Solution
A magnetless cryogenic circulator is designed using Nb/AlOx/Nb JJs, incorporating tunable inductors and resonators with angular momentum biasing through spatiotemporal modulation, monolithically integrated with microstrip delay lines and rf-SQUIDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional ferrite circulators with permanent magnets are used, then non-reciprocal signal routing is achieved, but magnetic field interference occurs that makes them unsuitable for quantum computing
Solution Approach 1:
The patent extracts and removes the permanent magnets from the circulator design, eliminating the source of magnetic field interference while maintaining the non-reciprocal signal routing function through an alternative mechanism based on time-varying impedance modulation
Solution Approach 2:
The patent replaces the magnetic field-based non-reciprocity mechanism with an electrical impedance modulation mechanism using time-varying capacitors or inductors, substituting the physical magnetic field approach with an electrical control approach that is compatible with quantum computing environments
2Object-affected harmful factors
If magnet-free circulators using varactors are used, then magnetic field interference is eliminated, but compatibility with low temperature superconductivity is lost
Solution Approach 1:
The patent changes the operating parameters and material properties of the circulator components to be compatible with cryogenic temperatures, using superconducting materials and designing the impedance modulation mechanism to function effectively at low temperatures where superconductivity occurs
Solution Approach 2:
The patent employs composite structures combining superconducting materials with conventional microwave circuit elements, creating a hybrid system that leverages the zero-resistance properties of superconductors at low temperatures while maintaining the necessary electrical characteristics for circulator operation
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 circulator achieves non-reciprocal signal routing without magnetic fields, compatible with quantum computing circuits, demonstrating high isolation, low insertion loss, and return loss.
Implementation Method 1
A set of tunable inductors modulated with modulation signals that have a relative phase angle of 0°, 120° and 240° are provided in the circuit. The resonators are modulated in time configured to lift the degeneracy of the two inherent counter-rotating modes, achieving a non-reciprocal signal routing.
Implementation Method 2
The capacitors and inductors are monolithically integrated and fabricated using a multi-layer Nb-based process with Nb/AlOx/Nb JJs.
Implementation Method 3
The circulator further has a microstrip delay line for providing the modulation signal to the set of resonators.
Data Source
AI summary
A magnetless cryogenic circulator is developed that has three identical resonators in three branches. Each branch connects two ports and each resonator has a capacitor connected across a tunable inductor. A set of tunable inductors modulated with modulation signals that have a relative phase of 0°, 120° and 240° provided through a circuit. A microstrip delay line for providing the modulation signal to the three resonators, wherein the resonators are modulated in time such that the degeneracy of the two inherent counter-rotating modes is lifted, achieving a non-reciprocal signal routing. All capacitors and inductors are monolithically integrated and fabricated using a multi-layer Nb-based process with Nb/AlOx/Nb JJs.