Sensing chiral magnetic noise via quantum impurity relaxometry

TL;DR

This paper develops a theory for quantum impurity relaxometry of magnons in thin films, demonstrating how chiral coupling influences impurity relaxation and enabling the sensing of chiral magnetic noise, with experimental validation on nickel films.

Contribution

It introduces a quantitative theoretical model for impurity relaxometry that accounts for chiral coupling, validated by experiments, advancing understanding of magnonic interactions and decoherence in quantum systems.

Findings

Chiral coupling is central to impurity relaxation.

The theory matches experimental data without arbitrary scale factors.

Quantum impurities can sense chiral magnetic noise.

Abstract

We present a theory for quantum impurity relaxometry of magnons in thin films, exhibiting quantitative agreement with recent experiments without needing arbitrary scale factors used in theoretical models thus far. Our theory reveals that chiral coupling between prototypical spin>1/2 quantum impurities and magnons plays a central role in determining impurity relaxation, which is further corroborated by our experiments on nickel films interfaced with nitrogen-vacancy centers. Along with advancing magnonics and understanding decoherence in hybrid quantum platforms with magnets, the ability of a quantum impurity spin to sense chiral magnetic noise presents an opportunity to probe chiral phenomena in condensed matter.