Nonreciprocal magnon–magnon entanglement based on magnon Kerr effect

We propose a theoretical scheme for the achievement of the nonreciprocal magnon–magnon entanglement in a magnomechanical system consisting of two coupled magnon modes and a mechanical mode, where one of the magnon modes couples to the mechanical mode via magnetostrictive interaction. In the experimental feasible parameters, the steady-state magnon–magnon entanglement and magnon–phonon entanglement can be generated by the entanglement transfer from magnomechanical entanglement source. More importantly, the magnon–magnon entanglement shows the ideal nonreciprocity when the magnon Kerr effect is considered. Furthermore, not only the nonreciprocity but also the degree of the magnon–magnon entanglement and its robustness with respect to the environmental temperature can be effectively enhanced by increasing the strengths of the magnon Kerr effect and the magnon–magnon coupling. Our scheme provides an alternative way to manipulate nonreciprocal quantum effect in the multipartite system.