Electron spins are amongst the most coherent solid-state systems known. However, to be used in devices for quantum sensing and information processing applications, they must typically be placed near interfaces. Understanding and mitigating the impacts of such interfaces on the coherence and spectral properties of electron spins is critical to realizing such applications, but it is also challenging: Inferring such data from single-spin studies requires many measurements to obtain meaningful results, while ensemble measurements typically give averaged results that hide critical information. Here, we report a comprehensive study of the coherence of near-surface bismuth donor spins in 28-silicon at millikelvin temperatures. In particular, we use strain-induced frequency shifts caused by a metallic electrode to infer spatial maps of spin coherence as a function of position relative to the electrode. By measuring magnetic-field-insensitive clock transitions, we separate magnetic noise caused by surface spins from charge noise. Our results include quantitative models of the strain-split spin resonance spectra and extraction of paramagnetic impurity concentrations at the silicon surface. The interplay of these decoherence mechanisms for such near-surface electron spins is critical for their application in quantum technologies, while the combination of the strain splitting and clock transition extends the coherence lifetimes by up to 2 orders of magnitude, reaching up to 300 ms at a mean depth of only 100 nm. The technique we introduce here to spatially map coherence in near-surface ensembles is directly applicable to other spin systems of active interest, such as defects in diamond, silicon carbide, and rare earth ions in optical crystals.

中文翻译：

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金属电极应变硅中供体自旋的空间分辨退相干

电子自旋是已知的最相干的固态系统之一。然而，要用于量子传感和信息处理应用的设备，它们通常必须放置在界面附近。了解并减轻此类界面对电子自旋的相干性和光谱特性的影响对于实现此类应用至关重要，但也具有挑战性：从单自旋研究中推断此类数据需要进行多次测量才能获得有意义的结果，而整体测量通常给出隐藏关键信息的平均结果。在这里，我们报告了在毫开尔文温度下 28 硅中近表面铋供体自旋的相干性的综合研究。特别是，我们使用由金属电极引起的应变引起的频移来推断自旋相干的空间图，作为相对于电极的位置的函数。通过测量对磁场不敏感的时钟转换，我们将表面自旋引起的磁噪声与电荷噪声分开。我们的结果包括应变分裂自旋共振光谱的定量模型和硅表面顺磁性杂质浓度的提取。这些近表面电子自旋退相干机制的相互作用对于它们在量子技术中的应用至关重要，而应变分裂和时钟跃迁的结合将相干寿命延长了 2 个数量级，达到 300 ms平均深度仅为 100 nm。