Magnon-mediated spin entanglement in the strong-coupling regime

Abstract

We present that two spin defects (SDs) can be entangled through a magnon polariton mode, within the strong-coupling regime. The magnon polariton modes are provided by an antiferromagnetic (AFM) ${\mathrm{MnF}}_{2}$ layer, where the dispersion of the modes is characterized by the layer's thickness. The macroscopic quantum electrodynamics theory is used to describe the light-matter interactions, where the Green's functions are its core elements. The individual SD relaxes by exciting the magnon polariton modes, exhibiting high enhancement values of the Purcell factor. When two SDs are considered, an oscillatory exchange of population probability is observed between them, a sign of strong-coupling light-matter interactions, where the concurrence value is used to quantify the level of entanglement. The thinner AF layers can potentially be used to promote interactions between multiple spins through long-range coupling. This is a desired feature to fabricate high-demand applications in the fields of quantum measurement and computation.