Tripartite high-dimensional magnon-photon entanglement in phases with broken PT -symmetry of a non-Hermitian hybrid system

Hybrid systems that combine spin ensembles and superconducting circuits provide a promising platform for implementing quantum information processing. We propose a non-Hermitian magnon-circuit-QED hybrid model consisting of two cavities and an yttrium iron garnet (YIG) sphere placed in one of the cavities. Abundant exceptional points (EPs), parity-time ($\mathcal{PT}$)-symmetry phases, and $\mathcal{PT}$-symmetry broken phases are investigated in the parameter space. Tripartite high-dimensional entangled states can be generated steadily among modes of the magnon and photons in $\mathcal{PT}$-symmetry broken phases, corresponding to which the stable quantum coherence exists. Results show that the tripartite high-dimensional entangled state is robust against the dissipation of hybrid system, independent of a certain initial state, and insensitive to the fluctuation of magnon-photon coupling. Further, we propose to simulate the hybrid model with an equivalent $LCR$ circuit. This paper may provide prospects for realizing multipartite high-dimensional entangled states in the magnon-circuit-QED hybrid system.