Search

Based on the phenomenon of exceptional points (EPs) in the optomechanically induced mechanical P T -symmetric binary and ternary systems, we propose a mechanism to generate the perfect one-way quantum steering between two totally symmetric modes, respectively. By investigating the quantum steering behavior in the close vicinity of EP, we find that the optimal one-way quantum steering can be successfully generated at the EP in the P T -symmetric binary mechanical system. When pushing the system towards the EP, we show that not only is the broadest region of the one-way quantum steering achieved, but the robustness against the thermal noise can be significantly enhanced. In addition, the direction of the one-way quantum steering can be precisely controlled only by altering the sign of the detuning of the cavity field. What's more, we analyze the mean populations of the involved modes to further support our findings and find that the occurrence of the one-way quantum steering depends mainly on the difference in the populations between the two target modes. We also successfully extend our findings to the high-order EP, and the desired one-way quantum steering can still be generated in the P T -symmetric ternary mechanical system when it operates at the EP. Our scheme opens up an alternative manipulation method to explore the various novel quantum effects exploiting the EPs and has significant potential applications in quantum nonreciprocal devices.

We propose a scheme to generate nonreciprocal photon blockade in a stationary whispering gallery microresonator system based on two physical mechanisms. One of the two mechanisms is inspired by recent work [Phys. Rev. Lett.128, 083604 (2022)10.1103/PhysRevLett.128.083604], where the quantum squeezing caused by parametric interaction not only shifts the optical frequency of propagating mode but also enhances its optomechanical coupling, resulting in a nonreciprocal conventional photon blockade phenomenon. On the other hand, we also give another mechanism to generate stronger nonreciprocity of photon correlation according to the destructive quantum interference. Comparing these two strategies, the required nonlinear strength of parametric interaction in the second one is smaller, and the broadband squeezed vacuum field used to eliminate thermalization noise is no longer needed. All analyses and optimal parameter relations are further verified by numerically simulating the quantum master equation. Our proposed scheme opens a new avenue for achieving the nonreciprocal single photon source without stringent requirements, which may have critical applications in quantum communication, quantum information processing, and topological photonics.