Quantum State Preparation of Ferromagnetic Magnons by Parametric Driving

TL;DR

This paper introduces a method to generate and detect Gaussian quantum states of ferromagnetic magnons using a longitudinal drive, leveraging spin-wave nonlinearity to produce squeezing and entanglement without single-magnon sources.

Contribution

It presents a novel approach to prepare and certify magnonic quantum states via purely magnonic nonlinearities, applicable to various ferromagnetic geometries.

Findings

Successfully generates vacuum-squeezed states of magnons.

Proposes classical detection methods for quantum states.

Analytical solutions for yttrium iron garnet ferrimagnets.

Abstract

We propose a method to prepare and certify Gaussian quantum states of the ferromagnetic resonance spin-wave modes in ferromagnets using a longitudinal drive. Contrary to quantum optics-based strategies, our approach harnesses a purely magnonic feature - the spin-wave nonlinearity - to generate magnon squeezing. This resource is used to prepare vacuum-squeezed states, as well as entangled states between modes of different magnets coupled via a microwave cavity. We propose methods to detect such states with classical methods, such as ferromagnetic resonance or local pickup coils, and quantify the required detection efficiency. We analytically solve the case of ellipsoidal yttrium iron garnet ferrimagnets, but our method applies to a vast range of shapes and sizes. Our work enables quantum magnonics experiments without single-magnon sources or detectors (qubits), thus bringing the quantum regime within reach of the wider magnonics community.