Superconducting Non-Reciprocity Based on Time-Modulated Coupled-Resonator Systems

TL;DR

This paper introduces a unified, theoretical and experimental approach for creating superconducting non-reciprocal devices like circulators and isolators using time-modulated coupled resonator networks with standard SQUID-based components.

Contribution

It presents a versatile design framework for superconducting non-reciprocal components, validated through experimental implementation of a superconducting isolator with high isolation and low insertion loss.

Findings

Achieved circulators and isolators with >20 dB isolation

Demonstrated a superconducting isolator with 1.3 dB insertion loss

Device exhibited >25 dB isolation at center frequency

Abstract

We present a unified approach for designing a diverse range of superconducting non-reciprocal components, including circulators, isolators, and uni-directional amplifiers, based on temporally-modulated coupled resonator networks. Our method leverages standard SQUID-based resonators as building blocks, arranged in various configurations such as series-coupled, wye-connected, and lattice-coupled resonators, to realize a wide range of on-chip non-reciprocal devices. Our theoretical studies demonstrated the effectiveness of the proposed approach, achieving circulators and isolators with near-zero insertion losses and isolation greater than 20 dB, and directional amplifiers with forward gain exceeding 10 dB and reverse isolation greater than 20 dB. To validate our findings, we implemented and measured a series-coupled three-resonator superconducting isolator using a single-layer superconducting process. At a base temperature of 20 mK, our device exhibited insertion loss of 1.3 dB in the forward direction, and isolation of up to 25 dB at the center frequency and greater than 15 dB across a bandwidth of 250 MHz in the reverse direction. Our approach promises to enable the design of a broad range of high-performance non-reciprocal devices for superconducting circuits.