Design of an on-chip superconducting microwave circulator with octave bandwidth

TL;DR

This paper introduces a superconducting on-chip microwave circulator with an octave bandwidth, enabling low-loss, high-isolation signal routing suitable for quantum computing readout systems.

Contribution

The design employs dynamically modulated switches and delays to achieve a broad bandwidth and high power handling, surpassing previous superconducting circulators.

Findings

Bandwidth of 2.3 GHz demonstrated in simulations

Insertion loss less than 0.35 dB

Isolation greater than 20 dB

Abstract

We present a design for a superconducting, on-chip circulator composed of dynamically modulated transfer switches and delays. Design goals are set for the multiplexed readout of superconducting qubits. Simulations of the device show that it allows for low-loss circulation (insertion loss < 0.35 dB and isolation >20 dB) over an instantaneous bandwidth of 2.3 GHz. As the device is estimated to be linear for input powers up to -65 dBm, this design improves on the bandwidth and power-handling of previous superconducting circulators by over a factor of 50, making it ideal for integration with broadband quantum limited amplifiers.