In this paper, we present a coherent feedback loop scheme to enhance the magnon–photon–phonon entanglement in cavity magnomechanics. We provide a proof that the steady state and dynamical state of the system form a genuine tripartite entanglement state. To quantify the entanglement in the bipartite subsystem and the genuine tripartite entanglement, we use the logarithmic negativity and the minimum residual contangle, respectively, in both the steady and dynamical regimes. We demonstrate the feasibility of our proposal by implementing it with experimentally realizable parameters to achieve the tripartite entanglement. We also show that the entanglement can be significantly improved with coherent feedback by appropriately tuning the reflective parameter of the beam splitter and that it is resistant to environmental thermalization. Our findings pave the way for enhancing entanglement in magnon–photon–phonon systems and may have potential applications in quantum information.

Coherence arises from the superposition principle, where it plays a central role in quantum me-chanics. In [Phys.Rev.Lett.114,210401(2015)], it has been shown that the freezing phenomenon of quantum correlations beyond entanglement, is intimately related to the freezing of quantum cohe-rence (QC). In this paper, we compare the behaviour of entanglement and quantum discord with quantum coherence in two di erent subsystems (optical and mechanical). We use respectively the en-tanglement of formation (EoF) and the Gaussian quantum discord (GQD) to quantify entanglement and quantum discord. Under thermal noise and optomechanical coupling e ects, we show that EoF, GQD and QC behave in the same way. Remarkably, when entanglement vanishes, GQD and QC re-main almost una ected by thermal noise, keeping non zero values even for high temperature, which in concordance with [Phys.Rev.Lett.114,210401(2015)]. Also, we nd that the coherence associated with the optical subsystem are more robustagainst thermal noisethan those of the mechanical subsystem. Our results con rm that optomechanical cavities constitute a powerful resource of QC. 1

No abstract

No abstract