The energy resolution per bandwidth $E_R$ is a figure of merit that combines the field resolution, bandwidth or duration of the measurement, and size of the sensed region. Several different dc magnetometer technologies approach $E_R=\hslash$, while to date none have surpassed this level. This suggests a technology-spanning quantum limit, a suggestion that is strengthened by model-based calculations for nitrogen-vacancy centers in diamond, for superconducting quantum interference device sensors, and for some optically pumped alkali-vapor magnetometers, all of which predict a quantum limit close to $E_R=\hslash$. This Colloquium reviews what is known about energy resolution limits, with the aim of understanding when and how $E_R$ is limited by quantum effects. A survey of reported sensitivity versus size of the sensed region for more than 20 magnetometer technologies is included, the known model-based quantum limits are reviewed, and possible sources for a technology-spanning limit are critically assessed, including zero-point fluctuations, magnetic self-interaction, and quantum speed limits. Finally, sensing approaches are described that appear to be unconstrained by any of the known limits, thus making them candidates to surpass $E_R=\hslash$.

中文翻译：

---

专题讨论会：量子限制磁场传感器的能量分辨率

每个带宽的能量分辨率 ${Ë}_{\mathrm{[R}}$是一个品质因数，它结合了场分辨率，测量的带宽或持续时间以及感应区域的大小。几种不同的直流磁力计技术方法${Ë}_{\mathrm{[R}}=\hslash$，到目前为止，没有任何一个超过这个水平。这表明了跨技术的量子极限，这一建议通过基于模型的钻石中氮空位中心，超导量子干涉仪传感器以及某些光泵浦碱蒸汽磁强计的基于模型的计算得到了加强，所有这些都预测了量子极限接近${Ë}_{\mathrm{[R}}=\hslash$。这次座谈会回顾了有关能量分辨率极限的知识，目的是了解何时何地${Ë}_{\mathrm{[R}}$受量子效应的限制。包括对超过20种磁力计技术的报告灵敏度与感测区域大小的调查，审查了基于模型的已知量子极限，并严格评估了技术极限的可能来源，包括零点波动，磁场自相互作用和量子速度限制。最后，描述了似乎不受任何已知限制约束的传感方法，因此使它们成为超越标准的候选方法${Ë}_{\mathrm{[R}}=\hslash$。