Abstract：
We demonstrate nearly a microsecond of spin coherence in Er3+ ions doped in cerium dioxide nanocrystal hosts, despite a large gyromagnetic ratio and nanometric proximity of the spin defect to the nanocrystal surface. The long spin coherence is enabled by reducing the dopant density below the instantaneous diffusion limit in a nuclear spin-free host material, reaching the limit of a single erbium spin defect per nanocrystal. We observe a large Orbach energy in a highly symmetric cubic site, further protecting the coherence in a qubit that would otherwise rapidly decohere. Spatially correlated electron spectroscopy measurements reveal the presence of Ce3+ at the nanocrystal surface, which likely acts as extraneous paramagnetic spin noise. Even with these factors, defect-embedded nanocrystal hosts show tremendous promise for quantum sensing and quantum communication applications, with multiple avenues, including core-shell fabrication, redox tuning of oxygen vacancies, and organic surfactant modification, available to further enhance their spin coherence and functionality in the future.
摘要：
我们证明了掺杂在二氧化铈纳米晶体基质中的Er3离子中的自旋相干性近一微秒，尽管大的旋磁比和自旋缺陷与纳米晶体表面的纳米接近度。通过将掺杂剂密度降低到无原子核自旋基质材料中的瞬时扩散限制以下，可以实现长自旋相干性。达到每个纳米晶体单个铒自旋缺陷的极限。我们在一个高度对称的立方体中观察到一个巨大的Orbach能量，进一步保护量子比特中的相干性，否则该量子比特会迅速去中心化。空间相关的电子能谱测量揭示了纳米晶体表面上Ce3+的存在，这可能是外来的顺磁自旋噪声。即使有这些因素，嵌入缺陷的纳米晶体基质在量子传感和量子通信应用中显示出巨大的前景，有多种途径，包括核壳制造，氧空位的氧化还原调节，和有机表面活性剂改性，可用于在未来进一步增强它们的自旋一致性和功能。
