Simultaneous nonreciprocal conventional photon blockades of two independent optical modes by a two-level system

We propose a scheme to achieve nonreciprocal conventional photon blockades simultaneously in two independent optical modes, which are connected by a two-level system. In the case that only one optical mode is weakly driven, we find that strong nonreciprocal photon blockades of both optical modes can be observed. We show that, for both optical modes, the single-photon blockades happens by driving the nonlinear device from one side, while photon-induced tunneling appears when driving the system from the other side, which is attributed to the anharmonic eigenenergy spectrum constructed by resonantly coupling to a two-level system. According to photon resonance transition processes under different driving directions, the four optimal Fizeau-Sagnac shifts can be obtained to generate perfect nonreciprocal conventional photon blockades of both optical modes. Our study opens an avenue to simultaneously manipulate multiple nonreciprocal single-photon devices and may have potential applications in chiral quantum information processing.