# Quantum entanglement between two magnon modes via Kerr nonlinearity

## TL;DR

This paper proposes a method to generate and maintain quantum entanglement between two macroscopic magnon modes in YIGs using Kerr nonlinearity and strong microwave driving, with potential applications in quantum technologies.

## Contribution

It introduces a scheme to entangle two ferromagnetic samples via Kerr nonlinearity in a driven cavity system, demonstrating steady-state entanglement in massive magnetic materials.

## Key findings

- Entanglement between two magnon modes is achieved via Kerr nonlinearity.
- Steady-state entanglement persists under strong microwave driving.
- The scheme provides a pathway for observing quantum effects in macroscopic magnetic systems.

## Abstract

We propose a scheme to entangle two magnon modes via Kerr nonlinear effect when driving the systems far-from-equilibrium. We consider two macroscopic yttrium iron garnets (YIGs) interacting with a single-mode microcavity through the magnetic dipole coupling. The Kittel mode describing the collective excitations of large number of spins are excited through driving cavity with a strong microwave field. We demonstrate how the Kerr nonlineraity creates the entangled quantum states between the two macroscopic ferromagnetic samples, when the microcavity is strongly driven by a blue-detuned microwave field. Such quantum entanglement survives at the steady state. Our work offers new insights and guidance to designate the experiments for observing the entanglement in massive ferromagnetic materials. It can also find broad applications in macroscopic quantum effects and magnetic spintronics.