Magnon heralding in cavity optomagnonics*

Cavity optomagnonics is an emergent field where photons couple to elementary magnetic excitations in solid state systems. For optical photons, the coupling is parametric and the magnetic material is both the optical cavity and the host of the magnetic excitations (magnons). These systems are promising for integration in hybrid quantum platforms. In this context, we propose a magnon heralding protocol to generate a magnon Fock state by detecting a cavity photon. We analyze the constraints imposed by the magnonic decay rate and by the strength of the optomagnonic coupling. We show that the detrimental thermal effects can be overcome by initially actively cooling the magnon mode. We discuss the feasibility of the proposed protocol for state of the art YIG cavity optomagnonic systems.