# Nonreciprocal unconventional photon blockade in a spinning optomechanical system

## TL;DR

This paper demonstrates how a spinning optomechanical system can produce nonreciprocal unconventional photon blockade, enabling direction-dependent quantum light control with potential applications in quantum photonic devices.

## Contribution

It introduces a novel nonreciprocal UPB mechanism in a spinning optomechanical system leveraging Fizeau drag effects, even with weak nonlinearity.

## Key findings

- Nonreciprocal UPB achieved via Fizeau drag in spinning resonators.
- Strong photon antibunching occurs only when driven from one side.
- Potential applications in quantum diodes and chiral photonic devices.

## Abstract

We propose how to achieve quantum nonreciprocity via unconventional photon blockade (UPB) in a compound device consisting of an optical harmonic resonator and a spinning optomechanical resonator. We show that, even with an extremely weak single-photon nonlinearity, nonreciprocal UPB can emerge in this system, i.e., strong photon antibunching can emerge only by driving the device from one side, but not from the other side. This nonreciprocity results from the Fizeau drag, leading to different splitting of the resonance frequencies for the counter-circulating modes. Such nonreciprocal quantum UPB devices can be particularly useful in achieving e.g., few-photon diodes or circulators, and quantum chiral photonic engineering.