Enhancement of Nonreciprocal Entanglement and Transmission via Phase-Dependent Unidirectional Coupling

The nonreciprocal property of quantum systems is crucial for chiral quantum networks. In this study, a phase-controlled scheme is proposed to enhance the nonreciprocal quantum entanglement and optical transmission in a cavity optomechanical system by introducing a phase-dependent unidirectional coupling between two whispering-gallery-mode (WGM) resonators. The Sagnac effect induced by the spinning resonator generates nonreciprocity, while the interference effect between direct evanescent coupling and indirect phase-dependent unidirectional coupling significantly enhances entanglement under the anti-Stokes sideband. For specific coupling phases, ideal nonreciprocity can be achieved in both entanglement and transmission. The proposed phase-controlled nonreciprocity presented offers an effective strategy for constructing a unidirectional quantum channel and implementing an optical diode in chiral quantum networks, thereby opening up new possibilities for applications in quantum technologies.