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arXiv · 2507.02278

Phase-locked amplification enhanced by spin squeezing

Yan Zhang·Jing Zhang·Hou Ian
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Abstract

Quantum lock-in amplification raises the detection sensitivity of magnetic fields to unprecedented levels by phase-locked pumping the Zeeman levels of a single trapped atom. However, random spin precessions limits the useful detection range of arming times for locking high-contrast signals. To extend this range imposed by the uncertainty limit, quadrature spin squeezing can be introduced, on top of the phase-locking mechanism. We propose a detection scheme using an atomic ensemble whose collected spin is pumped by two lasers for simultaneous squeezing and phase locking. We derive the optimal $\pi/2$-pulse and $\pi$-pulse schemes that accomplishes this concurrent action and prove that the resulting phase sensitivity is enhanced while the usable detection window for phase locking is widened.

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Yan Zhang, Jing Zhang, Hou Ian. 2025-07-03. Phase-locked amplification enhanced by spin squeezing. https://arxiv.org/abs/2507.02278

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