标题： 超灵敏磁强计的进动铁磁体的微观理论 显示英文标题

标题： Microscopic theory of a precessing ferromagnet for ultrasensitive magnetometry

摘要： 悬浮系统在量子传感以及探索宏观尺度的量子效应方面具有巨大潜力。 特别引人关注的是最近的研究表明，一个悬浮的铁磁体能够突破磁强计的标准量子极限。 本文提出了一种理论模型，用于分析和理解悬浮铁磁针（在弱磁场下表现出类似大自旋的行为）的进动动力学的关键特性。 从原子尺度的动力学揭示了如何超越标准量子极限，从而验证了与独立自旋集合相比的传感优势。 我们的理论还引导我们研究了两个具有实际意义的实验设计：通过进动铁磁针测量著名的Berry相位，以及利用其章动运动来探测低频振荡磁场。 随着悬浮铁磁针微观理论的建立，宏观量子效应及其相关的量子-经典过渡的未来研究也成为可能。 显示英文摘要

摘要： 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.