Superconducting Tunnel Junction Microwave Circulator
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Solution Overview
Problem
Commercially available microwave circulators are unsuitable for large-scale integration with superconducting quantum circuits due to their size and requirement for strong magnetic fields, and existing on-chip circulators suffer from strong non-linearity, limited bandwidth, and sensitivity to external bias perturbations.
Innovation Solution
A microwave circulator design featuring multiple ring segments with superconducting tunnel junctions that undergo a phase shift when biased, allowing signal propagation between ports while maintaining linearity and high bandwidth, and being robust to external perturbations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If commercially available microwave circulators are used, then signal routing and isolation are achieved, but device size and magnetic field requirements prevent large-scale integration with superconducting quantum circuits
Solution Approach 1:
The patent replaces traditional wave-interference-based circulator mechanisms with a superconducting quantum circuit implementation using Josephson junctions. This substitution enables on-chip integration while maintaining circulator functionality, directly addressing the size and integration constraints of commercial devices.
Solution Approach 2:
The invention changes the operating parameters by using superconducting materials and quantum tunneling effects instead of classical electromagnetic wave interference. This parameter change enables the circulator to function at microwave frequencies with on-chip dimensions suitable for integration with superconducting quantum circuits.
2Power
If existing on-chip circulator designs are used, then integration is achieved, but strong non-linearity limits signal power to small values
Solution Approach 1:
The circulator is divided into multiple discrete Josephson junctions arranged in a ring structure. Each junction contributes to the overall circulator effect, and the segmented design allows for better control of non-linearities while enabling higher power operation through the collective behavior of the junctions.
Solution Approach 2:
The invention uses composite superconducting structures combining multiple Josephson junctions with different characteristics. This composite approach allows optimization of the overall device performance, achieving both higher power handling and improved linearity by balancing the contributions of individual junctions.
3Adaptability or versatility
If existing on-chip circulator designs are used, then integration is achieved, but limited bandwidth restricts frequency range operation
Solution Approach 1:
The superconducting ring circulator design provides a universal platform that can operate across a broad frequency range by adjusting the bias conditions and junction parameters. The same basic structure serves multiple frequency bands, achieving high bandwidth without proportionally increasing device complexity.
4Reliability
If existing on-chip circulator designs are used, then integration is achieved, but high sensitivity to external bias perturbations degrades performance stability
Solution Approach 1:
The invention incorporates feedback mechanisms through the superconducting quantum interference effect, where the state of each Josephson junction is influenced by the magnetic flux through the entire ring. This creates an intrinsic feedback that stabilizes the circulator operation against external bias perturbations, as deviations are compensated by the quantum interference conditions.
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 design enables the construction of a highly linear and high-bandwidth microwave circulator suitable for on-chip integration with superconducting quantum circuits, capable of circulating higher power signals and less sensitive to external biases.
Implementation Method 1
at least one superconducting tunnel junction interconnecting each pair of adjacent ring segments in a circulator ring, wherein the tunnel junctions are configured so that when a bias is applied to the tunnel junctions, signals undergo a phase shift as they traverse the tunnel junctions between ring segments
Data Source
AI summary
A microwave circulator including an integrated circuit having a number of ports and a respective ring segment coupled to each port to allow microwave frequency signals to be transferred between the port and the respective ring segment. The circulator includes multiple respective ring segments arranged to define multiple parallel circulator rings and at least one superconducting tunnel junction interconnecting each pair of adjacent ring segments and/or a plurality of superconducting tunnel junctions interconnecting each pair of adjacent ring segments to form a circulator ring. The ring segments are configured so that when a bias is applied to the tunnel junctions, signals undergo a phase shift as they traverse the tunnel junctions between ring segments, thereby propagating signals to an adjacent port in a propagation direction.