Quantum Metrology with Higher-order Exceptional Points in Atom-cavity Magnonics

TL;DR

This paper proposes a method to create higher-order exceptional points in atom-cavity systems using Hermitian interactions, significantly enhancing quantum metrology sensitivity while avoiding noise issues present in non-Hermitian systems.

Contribution

It introduces a protocol for constructing higher-order EPs in atom-cavity systems via Hermitian magnon-photon interactions, enabling noise-free sensitivity enhancement in quantum metrology.

Findings

Demonstrates EP3/4-based atomic sensor with much higher sensitivity than EP2-based sensors.

Provides a general analysis for constructing arbitrary-order EPs.

Suggests experimental setups with potential candidates for implementation.

Abstract

Exceptional points (EPs), which arose early from non-Hermitian physics, significantly amplify the system's response to minor perturbations, and they act as a useful concept to enhance measurement in metrology. In particular, such a metrological enhancement grows dramatically with the EP's order. However, the Langevin noises intrinsically existing in the non-Hermitian systems diminish this enhancement. In this study, we propose a protocol for quantum metrology with the construction of higher-order EPs (HOEPs) in an atom-cavity system through Hermitian magnon-photon interaction. The construction of HOEPs utilizes the atom-cavity non-Hermitian-like dynamical behavior but avoids the external Langevin noises via the Hermitian interaction. A general analysis is exhibited for the construction of arbitrary -order EP (EPn). As a demonstration of the superiority of these HOEPs in quantum metrology, we work out an EP3/4-based atomic sensor with sensitivity being orders of magnitude higher than that achievable in an EP2-based atomic sensor. We further unveil the mechanism behind the sensitivity enhancement from HOEPs. The experimental establishment for this proposal is suggested with potential candidates. This EP-based atomic sensor, taking advantage of the atom-light interface, offers new insight into quantum metrology with HOEPs.