A low-loss ferrite circulator as a tunable chiral quantum system

TL;DR

This paper presents a low-loss, tunable ferrite circulator integrated with superconducting circuits, analyzing it as a multi-mode quantum system with coherent magnon-photon coupling, enabling non-reciprocal interactions.

Contribution

It demonstrates a novel low-loss ferrite circulator as a multi-mode quantum system and explores its potential for non-reciprocal quantum interactions in circuit QED.

Findings

Coherent coupling of chiral modes with superconducting cavities

Tunability of non-reciprocal interactions

Experimental observation of non-Hermitian dynamics

Abstract

Ferrite microwave circulators allow one to control the directional flow of microwave signals and noise, and thus play a crucial role in present-day superconducting quantum technology. They are typically viewed as a black-box, and their internal structure is not specified, let alone used as a resource. In this work, we demonstrate a low-loss waveguide circulator constructed with single-crystalline yttrium iron garnet (YIG) in a 3D cavity, and analyze it as a multi-mode hybrid quantum system with coupled photonic and magnonic excitations. We show the coherent coupling of its chiral internal modes with integrated superconducting niobium cavities, and how this enables tunable non-reciprocal interactions between the intra-cavity photons. We also probe experimentally the effective non-Hermitian dynamics of this system and its effective non-reciprocal eigenmodes. The device platform provides a test bed for implementing non-reciprocal interactions in open-system circuit QED.