Protection of centre spin coherence by dynamic nuclear spin polarization in diamond

We experimentally investigate the protection of electron spin coherence of a nitrogen-vacancy (NV) centre in diamond by dynamic nuclear spin polarization (DNP). The electron spin decoherence of an NV centre is caused by the magnetic field fluctuation of the C-13 nuclear spin bath, which contributes large thermal fluctuation to the centre electron spin when it is in an equilibrium state at room temperature. To address this issue, we continuously transfer the angular momentum from electron spin to nuclear spins, and pump the nuclear spin bath to a polarized state under the Hartmann-Hahn condition. The bath polarization effect is verified by the observation of prolongation of the electron spin coherence time (T-2*). Optimal conditions for the DNP process, including the pumping pulse duration and repeat numbers, are proposed by numerical simulation and confirmed by experiment. We also studied the depolarization effect of laser pulses. Our results provide a new route for quantum information processing and quantum simulation using the polarized nuclear spin bath.

我们通过动态核自旋极化（DNP）对金刚石中氮 - 空位（NV）中心的电子自旋相干性保护进行了实验研究。NV中心的电子自旋退相干是由碳 - 13核自旋库的磁场涨落引起的，当它在室温下处于平衡态时，会对中心电子自旋产生较大的热涨落。为了解决这个问题，我们不断地将角动量从电子自旋转移到核自旋，并在哈特曼 - 哈恩条件下将核自旋库泵浦到极化态。通过观察电子自旋相干时间（T - 2*）的延长验证了库极化效应。通过数值模拟提出了DNP过程的最佳条件，包括泵浦脉冲持续时间和重复次数，并通过实验得到了证实。我们还研究了激光脉冲的退极化效应。我们的研究结果为利用极化核自旋库进行量子信息处理和量子模拟提供了一条新途径。