Nonreciprocal waveguide-QED for spinning cavities with multiple coupling points

TL;DR

This paper demonstrates how spinning cavities with multiple coupling points can achieve nonreciprocal photon transmission and chiral emission, enabling advanced quantum nonreciprocal devices and large-scale quantum networks.

Contribution

It introduces a novel mechanism for nonreciprocal photon transmission using spinning cavities with multiple coupling points, leveraging interference and Sagnac effects.

Findings

Nonreciprocal photon transmission achieved in cavity-waveguide system.

Chiral emission can be optimized to approach perfect directionality.

Complete photon transmission in one direction over broad frequency range.

Abstract

We investigate chiral emission and the single-photon scattering of spinning cavities coupled to a meandering waveguide at multiple coupling points. It is shown that nonreciprocal photon transmissions occur in the cavities-waveguide system, which stems from interference effects among different coupling points, and frequency shifts induced by the Sagnac effect. The nonlocal interference is akin to the mechanism in giant atoms. In the single-cavity setup, by optimizing the spinning velocity and number of coupling points, the chiral factor can approach 1, and the chiral direction can be freely switched. Moreover, destructive interference gives rise to the complete photon transmission in one direction over the whole optical frequency band, with no analogy in other quantum setups. In the multiple-cavity system, we also investigate the photon transport properties. The results indicate a directional information flow between different nodes. Our proposal provides a novel way to achieve quantum nonreciprocal devices, which can be applied in large-scale quantum chiral networks with optical waveguides.