自主设备的临界传感：锁频NV中心磁力计的自振荡阈值
Critical Sensing with Autonomous Devices: The Self-Oscillation Threshold of a Frequency-Locked NV-Centre Magnetometer
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中文总结 AI 辅助
研究自主设备临界传感中锁频NV中心磁力计的自振荡阈值，通过提高软件环路增益使反馈映射经历分岔，推导阈值条件，进行可识别性分析并报告测量结果，揭示了该阈值与相关物理参数及波动的关系。
中文摘要 AI 辅助
反馈锁定探测频率到自旋共振是精密量子传感器的标准操作模式。本文我们有意在其稳定区域之外操作这种锁定：一个连续波氮空位（NV）系综磁力计，通过调频（FM）锁定到其光探测磁共振（ODMR）的一侧，通过提高软件环路增益$G$，使其离散反馈映射经历翻转（倍周期）分岔。超过临界增益$\Gc$，锁定变为自持振荡器，其极限环由环路自身产生。我们推导了阈值条件$\Gc = 2\,\Dcal/\Dtrue$，确定了阈值的可测量内容：校准时刻$D_{cal}$的ODMR锁定信号的转换斜率与其当前值$D_{true}$的比值。我们进行了可识别性分析，表明这个单一标量能区分和不能区分哪些物理参数，在实际噪声下表征了$\Gc$的估计器，并报告了我们当前设置的测量结果：一个实验分岔图，起始于$\Gc \approx 2$，如自校准环路所预测，亚阈值临界波动遵循预测的$\sqrt{G/(2 - G)}$发散。
英文摘要
Feedback locking of a probe frequency to a spin resonance is the standard operating mode of precision quantum sensors. Here we deliberately operate such a lock outside its stable regime: a continuous-wave nitrogen-vacancy (NV) ensemble magnetometer, frequency-modulation (FM) locked to one flank of its optically detected magnetic resonance (ODMR), is driven through the flip (period-doubling) bifurcation of its discrete feedback map by raising the software loop gain $G$. Beyond a critical gain $\Gc$ the lock becomes a self-sustained oscillator whose limit cycle is generated by the loop itself. We derive the threshold condition $\Gc = 2\,\Dcal/\Dtrue$, which identifies the measurable content of the threshold: the ratio of the transduction slope of the ODMR lock-in signal at calibration time $D_{cal}$ to its value at present $D_{true}$. We present an identifiability analysis showing which physical parameters this single scalar can and cannot distinguish, characterize the estimators of $\Gc$ under realistic noise, and report measurements on our current setup: an experimental bifurcation diagram with onset at $\Gc \approx 2$ as predicted for a self-calibrated loop, sub-threshold critical fluctuations following the predicted $\sqrt{G/(2-G)}$ divergence.
