Entangling cavity-magnon polaritons by interacting with phonons

Abstract We show how to entangle two cavity-magnon polaritons (CMPs) formed by two strongly coupled microwave cavity and magnon modes. This is realized by introducing vibration phonons, via magnetostriction, into the system that are dispersively coupled to the magnon mode. Stationary entanglement between two CMPs can be achieved when they are respectively resonant with the two sidebands of the drive field scattered by the phonons, and when the proportions of the cavity and magnon modes in the two polaritons are appropriately chosen. The entangled CMPs are macroscopic quantum states as the magnon mode contains a large number of spins, and can lead to the emission of frequency-entangled microwave photons, which find broad applications in microwave quantum information processing and quantum metrology.