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

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.

Dissimilar collective decay and directional emission from two quantum emitters

“…The proposed system can be implemented with field circulators, that are readily available for fiber optics and an active element of research in superconducting circuits [48,49] and integrated photonics [50,51]. These can be integrated into state-of-the art waveguide QED platforms [52].…”