Simultaneous nonreciprocal photon blockade via directional parametric amplification

We propose a scheme to achieve the simultaneous nonreciprocal photon blockade of two microring resonators in an all-optical system without any rotating parts. By unidirectionally parametrically pumping a χ(2)-nonlinear resonator with a classical coherent field, the counterclockwise mode in the resonator is exposed to the parametric amplification process when a forward signal field is input in another resonator, but not the case for a backward signal field. This leads to different quantum interference effects among distinct excitation paths for two optical modes, which is the essential reason for simultaneous nonreciprocal photon blockade. We analytically give the optimal parameter conditions to achieve simultaneous strong photon blockade with the parametric amplification. Furthermore, the nonreciprocity is simultaneously enhanced through tuning the amplitude of input signal. Our work provides an avenue to realize simultaneous nonreciprocal single-photon devices without moving parts and may have potential applications in many-body quantum information processing and quantum communication.