Nonreciprocal Coupling Induced Non‐Hermitian Entanglement in Optomechanical Systems
W. Y. Hu, H. Yi, H. N. Liu, S. Y. Ge, Cheng Shang, Yan‐Hui Zhou, H. Z. ShenABSTRACT
Quantum entanglement, one of the most intrinsic properties of quantum mechanics, corresponds to a key resource for quantum information. Exceptional points (EPs) are special phase transition points in non‐Hermitian systems. Nonreciprocity achieves one‐way motion by breaking reciprocal symmetries. However, the connections among quantum entanglement, EPs, and nonreciprocity remain unexplored in non‐Hermitian systems. In this paper, we investigate the manipulation of optomechanical entanglement by non‐Hermitian coupling between two counter‐propagating optical modes based on a whispering‐gallery‐mode (WGM) resonator coupled with two Rayleigh scatterers. The spinning resonator can induce opposite frequency shifts in two counter‐propagating optical modes. Moreover, EPs can periodically appear by controlling the relative angle between two nanoparticles. The logarithmic negativity of entanglement reaches the maximum at EPs, leading to significant enhancement of optomechanical entanglement. In contrast, the entanglement is suppressed at non‐EPs but can be recovered by the Sagnac–Fizeau shift. Specially, by driving the resonator at EPs while spinning it at the optimal rotation speed, we achieve switching between classical and quantum nonreciprocity.