Distinguishing photon blockade in a PT -symmetric optomechanical system

We study the effects of parity-time (PT) symmetry on the photon blockade and distinguish the different blockade mechanisms in a double-cavity optomechanical system. By studying the light statistics of the system, we find the completely different photon blockade behaviors when the PT symmetry is broken or unbroken, which is related to the PT phase transition. Furthermore, an interesting phenomenon that the two cavities are blocked at the same time is found with the appropriate system parameters. Those statistical phenomena are all analyzed in detail and demonstrated by analytically solving the Schrödinger equation and numerically simulating the master equation, respectively. Finally, we also consider the non-PT-symmetric situations which further reveal the physical essence of the photon blockade by comparing those results. Different from the usual photon blockade, our proposal is feasible even with weak parameter mechanism, i.e., the proposal neither requires the strong optomechanical coupling nor the large tunneling coupling between cavities.