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arXiv · 2503.00728

Microscopic theory of a precessing ferromagnet for ultrasensitive magnetometry

Xueqi Ni·Zhixing Zou·Ruvi Lecamwasam·Andrea Vinante·Dmitry Budker·Ping Koy Lam·Tao Wang·Jiangbin Gong
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Abstract

Levitated systems have great potential in quantum sensing and exploring quantum effects at the macroscopic scale. Of particular interest are recent works suggesting that a levitated ferromagnet can beat the standard quantum limit of magnetometry. This work offers a theoretical model to analyze and understand critical features of the precessing dynamics of a levitated ferromagnetic needle, indeed much like a macrospin, in the presence of a weak magnetic field. The dynamics from the atomic scale reveals how the standard quantum limit is surpassed, thus verifying sensing advantages when compared with a collection of independent spins. Our theory further takes us to two additional experimental designs of immediate interest: measurement of the celebrated Berry phase with a precessing ferromagnetic needle and the use of its nutation motion to sense a low-frequency oscillating magnetic field. With a microscopic theory established for levitated ferromagnetic needles, future studies of macroscopic quantum effects and the associated quantum-classical transition also become possible.

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Xueqi Ni, Zhixing Zou, Ruvi Lecamwasam, Andrea Vinante, Dmitry Budker, Ping Koy Lam, Tao Wang, Jiangbin Gong. 2025-03-02. Microscopic theory of a precessing ferromagnet for ultrasensitive magnetometry. https://doi.org/10.1103/1v1p-kpb2

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