AI 中文总结
本研究通过超高真空与环境条件对比实验，发现表面吸附物可抑制浅NV中心的低频噪声，揭示了其在调控噪声环境中的复杂作用，为纳米量子传感提供重要参考。
AI 中文摘要
金刚石中的浅氮空位（NV）中心是极具潜力的纳米尺度量子传感器，但其相干性受表面诱导噪声的强烈限制，表面吸附物被广泛认为是退相干的主要来源。本文通过在超高真空（UHV）条件下表征浅单NV中心（该条件下金刚石表面无吸附物），并与环境条件下的行为进行对比来验证这一假设。令人惊讶的是，我们观察到在UHV中，Hahn回波相干时间T2降低了约4倍。通过结合单量子（SQ）和双量子（DQ）基下的Hahn回波测量，我们分离出不同噪声源的贡献，发现UHV中电场和磁场噪声均增强。相比之下，T1测量显示UHV中的DQ T1增加，表明~100 MHz频率范围内的电场噪声被抑制。这些结果表明，去除吸附物后表面噪声谱发生改变，不同频率范围对应不同的微观机制。具体而言，低频噪声与UHV中增加的表面电荷一致，而环境条件下表面吸附物可补偿这些电荷。本研究揭示了表面吸附物在塑造浅NV中心噪声环境中复杂且此前未被充分认识的作用，对纳米尺度量子传感具有重要意义。
英文摘要
Shallow nitrogen-vacancy (NV) centers in diamond are promising nanoscale quantum sensors, yet their coherence is strongly limited by surface-induced noise. Surface adsorbates are widely believed to be a major source of decoherence. Here, we test this assumption by characterizing shallow single NV centers under ultrahigh vacuum (UHV) conditions, where the diamond surface is kept free of adsorbates, and comparing their behavior to ambient conditions. Surprisingly, we observe a ~4x reduction in the Hahn echo coherence time T2 in UHV. By combining Hahn echo measurements in the single-quantum (SQ) and double-quantum (DQ) bases, we separate contributions from different noise sources and find that both electric and magnetic noise are enhanced in UHV. In contrast, T1 measurements reveal an increased DQ T1 in UHV, indicating suppressed electric field noise in the ~100 MHz frequency regime. These results point to a modification of the surface noise spectrum upon adsorbate removal, with different frequency regimes arising from distinct microscopic mechanisms. Specifically, we find that the low frequency noise is consistent with increased surface charge in UHV that can be compensated by surface adsorbates in ambient conditions. Our findings highlight a complex and previously underappreciated role of surface adsorbates in shaping the noise environment of shallow NV centers, with important implications for nanoscale quantum sensing.
