Entanglement Enhancement by the Synergistic Effect of Optical Parametric Amplification and Coherent Feedback in Cavity Magnonics

Abstract The scheme is proposed to enhance the entanglement in cavity‐magnonics system by exploiting the synergistic effects of an optical parametric amplifier (OPA) and coherent feedback. In the system, the two cavities are arranged in a cross‐shaped, with a yttrium iron garnet (YIG) sphere positioned near the intersection of the cross‐shaped cavities. By introducing coherent feedback, the energy dissipated by the horizontal cavity can be fed back into the vertical cavity, which can be compensated via OPA. The nonlinear gain of OPA and reflectivity of the coherent feedback play important roles in the dynamics of the system and enable enhancement of both bipartite and tripartite entanglement as compared to the system without OPA and coherent feedback. The robustness of entanglement against environment temperature can also be greatly improved. Moreover, in the system that possesses a symmetrical structure but demonstrates asymmetric energy flow, controllable one‐way steering can be realized through the precise adjustment of specific parameters within the system. The scheme offers a novel approach to realize high‐quality entanglement resources and holds potential applications in quantum information processing and quantum communication.