基于金刚石NV色心系综磁强计相干布局振荡研究

Coherent Population Oscillation of Magnetometer Based on Diamond NV Color Center Ensemble

本文介绍了我们通过利用两路微波共同作用下来进行NV色心的量子调控,实验结果出现"烧孔"现象并降低线宽,与此同时得到直流磁噪声灵敏度。在连续波实验条件下,两路微波都调谐到NV色心系综基态3A2之间的共振频率,一路泵浦微波(Pump)设定为给定的频率(ms=0?ms=±1),一路探测微波(Probe)设定为扫频。在本次实验中我们关注的是两个微波场在NV基态之间跃迁相同的情况(ms=0?ms=+1)。在这种方法下,观察到的光谱表现出一个复杂的窄线宽结构,当探测微波功率一定时,泵浦微波功率越低,线宽越窄。当泵浦微波功率不变,改变微波频率时,烧孔一直出现在改变的微波频率处,最后我们对信号进行了调制解调,由于NV色心系综磁检测的灵敏度与解调曲线的最大斜率成反比,发现相干布局现象的调制斜率提高了20%,进一步提高了直流散粒噪声灵敏度。

The magnetometer based on ensembles of NV centers has attracted much attention within the fields of quantum information. As a new technology, NV center magnetometer can detect magnetic field with high sensitivity and spatial resolution at room temperature, which has broad application prospects in the fields of weak magnetic field measurement.We expect the highest sensitivity to be achieved by any method;the factors affecting the sensitivity are the contrast and linewidth, which depend on the microwave(MW) and light powers;are critical for optimizing magnetometer sensitivity based on high-density nitrogen vacancy(NV) centers in diamond. In this paper, we report a study of the coherent population oscillation based on ensembles of NV centers by using two microwave channels to control quantum state of NV centers. The notion of coherent population oscillation is widely used in the atomic physics/quantum optics community but is essentially unknown in the EPR/ODMR community. A home-made magnetic field detection system was set up to sense the external magnetic field and the experimental results of optically detected magnetic resonance show that the phenomenon of "hole burning" and the linewidth at the peak becomes narrower. We attribute the spectra to coherent population oscillations induced by the two nearly degenerate microwave fields. At the same time, because the sensitivity is related to the slope of signal modulation, the detected signal was demodulated with a lock-in amplifier referenced to the modulation frequency by a signal generator, the slope of microwave modulation signal increased from the experimental results. Under the condition of continuous wave experiment, both microwave channels are tuned to the resonance frequency between the ground state3 A2 of NV center ensembles, and the pump of one channel is set to a given frequency(ms = 0 ? ms = ±1), and the probe is set to sweep frequency. In this experiment, we attribute the resonances occurring on the same transition to the coherent population oscillations(CPO) resulting from interference(beating) between two coherent electromagnetic fields(ms = 0 ? ms = +1). Via this method, the observed optically detected magnetic resonance spectra showed a complex narrow linewidth structure and whether the shape of the hole would change under different microwave conditions was tested.When the detection microwave power is constant, the lower the pump microwave power, the narrower the linewidth. When the pump microwave power is constant and the microwave frequency is changed, the hole burning always appears at the changed microwave frequency, and the effect occurs only for beat frequencies within the range determined by the population relaxation times. Finally, we modulated the optically detected magnetic resonance signal by using sine wave. Because the sensitivity of NV color center ensemble magnetic detection is inversely proportional to the maximum slope of demodulation curve, it is found that the modulation slope of coherent layout phenomenon was increased by 20%, which further improved the shot-noise-limited sensitivity of DC. This article is just a basic experiment about coherent population oscillation, however it has a good application for achieving high precision measurement in the future and provides a good support for reducing linewidth.