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  • Letter
  • Open Access

Quantum metrology with higher-order exceptional points in atom-cavity magnonics

Minwei Shi1,2, Guzhi Bao1,2,3,*, Jinxian Guo1,2,3,†, and Weiping Zhang1,2,3,4,5,‡

  • 1Tsung Dao Lee Institute, Shanghai Jiao Tong University, Shanghai 200240, China
  • 2School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
  • 3Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
  • 4Shanghai Branch, Hefei National Laboratory, Shanghai 201315, China
  • 5Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China

  • *Contact author: guzhibao@sjtu.edu.cn
  • †Contact author: jxguo@sjtu.edu.cn
  • ‡Contact author: wpz@sjtu.edu.cn
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Phys. Rev. Research 7, L022034 – Published 9 May, 2025

DOI: https://doi.org/10.1103/PhysRevResearch.7.L022034

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 nth-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.

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Phys. Rev. Research 7, L022034– Published 9 May, 2025
  • Received 16 May 2024
  • Accepted 3 April 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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