Universal nonreciprocal photon blockade

We propose a scheme to simultaneously achieve nonreciprocal unconventional and conventional photon blockade in a single photonic resonator based on the joint of chiral cavity-atom coupling and parametric amplification, which significantly enhances the nonreciprocal photon blockade (NPB) and is termed universal NPB. We demonstrate that the nonreciprocal unconventional photon blockade dominates in weak coupling regime characterized by chiral and backscattering couplings smaller than decay rate when driving the device from one side but not from the other side, whereas the nonreciprocal unconventional and conventional photon blockades simultaneously account for the NPB in the strong coupling regime. This broadens the parameter space of realizing the NPB and demonstrates a stronger NPB in the strong coupling regime. Furthermore, the nonreciprocity can be improved by approximately three orders of magnitude due to the presence of the parametric amplification. Our findings pave the way for the development of quantum nonreciprocal devices, with potential applications in quantum information processing and chiral networks.