# Macroscopic entanglement of two magnon modes via quantum correlated microwave fields

## TL;DR

This paper proposes a practical scheme to generate steady-state entanglement between two macroscopic magnon modes in yttrium-iron-garnet spheres using quantum correlated microwave fields, demonstrating robustness and experimental feasibility.

## Contribution

The study introduces a novel method to entangle macroscopic magnon modes via microwave fields, leveraging linear state-swap interactions and realistic experimental parameters.

## Key findings

- Achieves significant magnon entanglement under feasible conditions
- Entanglement persists at temperatures up to hundreds of milliKelvin
- Demonstrates robustness against thermal effects

## Abstract

We present a scheme to entangle two magnon modes in two macroscopic yttrium-iron-garnet spheres. The two spheres are placed inside two microwave cavities, which are driven by a two-mode squeezed microwave field. By using the linear state-swap interaction between the cavity and the magnon mode in each cavity, the quantum correlation of the two driving fields is with high efficiency transferred to the two magnon modes. Considerable entanglement could be achieved under experimentally achievable conditions $g \gg \kappa_a \gg \kappa_m$, where $g$ is the cavity-magnon coupling rate and $\kappa_a$, $\kappa_m$ are the decay rates of the cavity and magnon modes, respectively. The entanglement is in the steady state and robust against temperature, surviving up to hundreds of milliKelvin with experimentally accessible two-mode squeezed source.