AI 中文总结
研究利用浅电子自旋进行量子传感时单个 NV 中心深度确定问题，提出自旋锁定核磁共振方法，通过特定频率调节及拟合函数，实现与现有方法高度一致的深度估计，确立其为可靠替代方法并用于研究金刚石上 1H 核自旋信号。
AI 中文摘要
利用浅电子自旋进行定量量子传感，如金刚石中氮空位（NV）中心的自旋，需要准确了解自旋在主体材料表面以下的深度。一种常用方法是从金刚石表面浸油的 1H 核磁共振（NMR）信号推断该深度，可使用 XY8 等动态解耦序列检测。但有限宽度脉冲使 XY8 对次谐波响应敏感，包括附近 13C 自旋的不必要贡献，且仪器受限的光谱分辨率仅对窄 1H NMR 线形进行稀疏采样。本文引入自旋锁定核磁共振作为确定单个 NV 深度的替代方法。通过将自旋锁定拉比频率调至 1H 拉莫尔频率，NV 通过哈特曼 - 哈恩共振探测 1H NMR 信号，无脉冲解耦序列的谐波模糊性且光谱分辨率更高。从马尔可夫主方程导出定量自旋锁定核磁共振拟合函数，直接将测量光谱与 NV 深度相关联。该方法在多个 NV 中心获得与基于 XY8 的既定协议高度一致的 NV 深度估计，确立了自旋锁定核磁共振作为定量单个 NV 深度测定的可靠替代方法。为证明其适用性，用该方法研究了即使在没有浸油的情况下金刚石上通常报道存在的 1H 核自旋信号。
英文摘要
Quantitative quantum sensing with shallow electron spins, such as those hosted by nitrogen-vacancy (NV) centers in diamond, requires accurate knowledge of the spin's depth below the host material's surface. A widely used approach infers this depth from the 1H nuclear magnetic resonance (NMR) signal of immersion oil on the diamond surface that can be detected using dynamical decoupling sequences such as XY8. However, finite-width pulses make XY8 sensitive to subharmonic responses, including unwanted contributions from nearby 13C spins, and its instrument-limited spectral resolution provides only sparse sampling of the narrow 1H NMR lineshape. Here, we introduce Spin-Lock NMR as an alternative approach to single-NV depth determination. By tuning the Spin-Lock Rabi frequency to the 1H Larmor frequency, the NV probes the 1H NMR signal through the Hartmann-Hahn resonance without the harmonic ambiguities of pulsed decoupling sequences and with substantially higher instrument-limited spectral resolution. We derive a quantitative Spin-Lock NMR fit function from a Markovian master equation that directly relates the measured spectrum to the NV depth. Our approach yields NV depth estimates in excellent agreement with the established XY8-based protocol across multiple NV centers and establishes Spin-Lock NMR as a robust alternative for quantitative single-NV depth determination. To demonstrate its applicability, we employ our method to investigate the 1H nuclear spin signal that is regularly reported to be present on diamond, even in the absence of immersion oil.
