超越标准量子极限的纠缠增强光学磁强计
Entanglement-enhanced optical magnetometry beyond the standard quantum limit
AI总结：
该研究针对光学原子磁强计受标准量子极限限制的问题，利用纠缠态与变分读出技术，在宽声学频率范围内实现了超越标准量子极限的灵敏度。
AI中文摘要：
光学原子磁强计是连续传感应用的强大工具，然而在缺乏量子关联的情况下，其灵敏度受限于标准量子极限（SQL），该极限源于光学探针不精确性与量子测量反作用之间的权衡。超越SQL的灵敏度需要能改变这些测量噪声源的量子关联。本文中，我们通过使用探针光的纠缠态并设计测量不精确性与反作用之间的关联，展示了此类灵敏度。我们首先在宽频率范围内探究了SQL，随后通过将变分读出与磁强计耦合到二分纠缠光态的一个模式、并基于另一个纠缠模式对结果进行条件处理，展示了克服该极限的方法。通过调节探测光正交分量并组合两个测量通道的信号，我们在宽声学频率范围内实现了超越SQL的灵敏度，而该范围此前是量子噪声受限光学磁强计无法企及的。
英文摘要：
Optical atomic magnetometry is a powerful tool for continuous sensing applications, yet, in the absence of quantum correlations, its sensitivity is limited by the standard quantum limit (SQL) stemming from a trade-off between optical probe imprecision and quantum measurement backaction. Beyond-SQL sensitivity requires quantum correlations that modify these measurement noise sources. Here we demonstrate such sensitivity by using entangled state of the probe light and by engineering correlations between measurement imprecision and backaction. Having first explored SQL in a broad range of frequencies, we demonstrate overcoming the limit by combining variational readout with coupling the magnetometer to one mode of a bipartite entangled light state and conditioning the results on the other entangled mode. Tuning the detected light quadratures and combining the signals from the two measurement channels, we achieve sensitivity beyond the SQL in a broad range of acoustic frequencies which has so far remained inaccessible to quantum-noise-limited optical magnetometry.
