金刚石NV^-色心系综自旋相干动力学解耦

Coherence Dynamic Decoupling for Spin of NV^- Color Center Ensemble in Diamond

室温条件下高浓度的NV^-色心系综的相干时间受到较高浓度顺磁杂质和杂质自旋的影响,限制着其高灵敏磁传感的实现。为了增加NV^-色心系综的相干时间,本文对系综的动力学解耦(DD)过程进行研究。在外部磁场为40 G的条件下,通过连续光学磁共振光谱技术(CW-ODMR),首先确定电子自旋态|m_s=0>→|m_s=±1>共振跃迁对应的微波频率;构建脉冲控制序列,观测不同微波功率条件下系综NV^-色心自旋电子态|m_s=0>→|m_s=+1>的相干Rabi振荡,获得最优功率的π脉冲作用时间;基于典型的CPMG-n控制序列,研究最优脉冲作用下不同π脉冲个数的DD过程。在最大输入微波功率为1.30 mW的条件下,获得的π脉冲长度为28.8 ns;结合CPMG-32控制脉冲序列,系综的典型相干时间由372(3) ns提升至8.7(1)μs。该研究结果为后续高灵敏量子磁检测的实现奠定了实验基础。

The spin coherence time of NV-with high concentration at room temperature is limited by the paramagnetic impurity and its spin, which is not conducive to the magnetic sensing with high sensitivity. To increase the coherence time, the dynamic decoupling(DD) process for NV^- color center ensemble is studied in this paper. When the external magnetic field is fixed at 40 G,the resonant microwave frequency of |ms=0>→|ms=±1> is determined via continuous-wave optical magnetic resonance(CW-ODMR) spectroscopy. The Rabi oscillations between the |ms=0>→|ms=+1> with different microwave power have been observed and the optimal π-pulse length can be determined. Based on the typical CPMG-n sequence, the DD process with different number of optimal π-pulse is also studied. At a maximum input power of 1.30 mW, the optimal π-pulse length is 28.8 ns. Combined with CPMG-32 sequence, the coherence time is increased from 372(3) ns to 8.7(1)μs. These results show that we already have the basic technology of improving the coherence time with manipulation of quantum state, which is the foundation for the quantum magnetic detection with high sensitivity.