Nonreciprocal unconventional photon blockade in a spinning optomechanical system

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 very 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 optical counter-circulating modes. Such quantum nonreciprocal devices can be particularly useful in achieving backaction-free quantum sensing or chiral photonic communications.