Bipartite entanglement and Gaussian quantum steering in a whispering gallery mode coupled with two magnon modes.

We theoretically propose a scheme to generate and control continuous variable bipartite entanglement and Gaussian quantum steering in an optical whispering gallery mode (WGM)-based cavity optomagnonical system that consists of two macroscopic YIG resonator. Owing to the well-known Faraday effect, both the magnon modes are coupled to single-mode optical WGM through nonlinear interaction. We investigate in detail the impact of several physical parameters such as effective cavity detuning, input laser power, environment temperature, optomagnonical coupling strengths and magnon decay rate on different bipartite entanglement. We also found a suitable parameter regime to obtain maximum cavity-magnon and magnon-magnon bipartite entanglement in our proposed system. It is interesting to note that the numerical simulation result shows that magnon-magnon entanglement persists up to 60K. With a proper choice of optomagnonical coupling strengths and normalized effective cavity detuning, we can effectively control the nature and strength of Gaussian quantum steering. In the WGM-based cavity optomagnonical system, our current work will offer a new way of greatly controlling a variety of nonclassical quantum correlations of macroscopic objects, which may find use in a number of contemporary quantum technology fields.