# Antiferromagnetic cavity optomagnonics

## TL;DR

This paper proposes a theoretical model for a multimode cavity optomagnonic system using antiferromagnetic insulators, exploring coherent interactions at THz frequencies with potential applications in quantum transduction and memory.

## Contribution

It introduces a novel multimode cavity optomagnonic system based on antiferromagnets, analyzing its unique tunable coupling and dark mode features for quantum information applications.

## Key findings

- Coupling can be tuned via magnetic field along the easy axis.
- System exhibits optomagnonically induced transparency with substructure.
- Unusual magnon heating occurs under red detuned driving.

## Abstract

Currently, there is a growing interest in studying the coherent interaction between magnetic systems and electromagnetic radiation in a cavity, prompted partly by possible applications in hybrid quantum systems. We propose a multimode cavity optomagnonic system based on antiferromagnetic insulators, where optical photons couple coherently to the two homogeneous magnon modes of the antiferromagnet. These have frequencies typically in the THz range, a regime so far mostly unexplored in the realm of coherent interactions, and which makes antiferromagnets attractive for quantum transduction from THz to optical frequencies. We derive the theoretical model for the coupled system, and show that it presents unique characteristics. In particular, if the antiferromagnet presents hard-axis magnetic anisotropy, the optomagnonic coupling can be tuned by a magnetic field applied along the easy axis. This allows to bring a selected magnon mode into and out of a dark mode, providing an alternative for a quantum memory protocol. The dynamical features of the driven system present unusual behavior due to optically induced magnon-magnon interactions, including regions of magnon heating for a red detuned driving laser. The multimode character of the system is evident in a substructure of the optomagnonically induced transparency window.