Passive microwave circulation on a superconducting chip

TL;DR

This paper demonstrates a passive, on-chip superconducting microwave circulator using a loop of tunnel-coupled islands, achieving non-reciprocal signal routing with low loss and high isolation, crucial for scalable quantum circuits.

Contribution

It introduces a novel on-chip superconducting circulator based on a loop of tunnel-coupled islands with DC control, enabling miniaturization of quantum microwave components.

Findings

Achieved 2 dB insertion loss at resonance

Demonstrated 14 dB isolation

Bandwidth of 200 MHz

Abstract

Building large-scale superconducting quantum circuits will require miniaturisation and integration of supporting devices including microwave circulators, which are currently bulky, stand-alone components. Here we report the realisation of a passive on-chip circulator which is made from a loop consisting of three tunnel-coupled superconducting islands, with DC-only control fields. We observe the effect of quasiparticle tunnelling, and we dynamically classify the system into different quasiparticle sectors. When tuned for circulation, the device exhibits strongly non-reciprocal 3-port scattering, with average on-resonance insertion loss of 2 dB, isolation of 14 dB, power reflectance of -11 dB, and a bandwidth of 200 MHz.