Clock transitions (CTs) in spin systems, which occur at avoided level crossings, enhance quantum coherence lifetimes T2 because the transition becomes immune to the decohering effects of magnetic field fluctuations to first order. We present the first electron-spin resonance characterization of CTs in certain defect-rich silica glasses, noting coherence times up to 16 μs at the CTs. We find CT behavior at zero magnetic field in borosilicate and aluminosilicate glasses, but not in a variety of silica glasses lacking boron or aluminum. Annealing reduces or eliminates the zero-field signal. Since boron and aluminum have the same valence and are acceptors when substituted for silicon, we suggest the observed CT behavior could be generated by a spin-1 boron vacancy center within the borosilicate glass, and similarly, an aluminum vacancy center in the aluminosilicate glass.

中文翻译：

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石英玻璃缺陷产生的时钟转换


自旋系统中的时钟跃迁 （CT） 发生在避免的电平交叉处，增强了量子相干寿命 T2，因为该跃迁对磁场波动的退相干效应免疫到一阶。我们首次提出了某些富含缺陷的二氧化硅玻璃中 CT 的电子-自旋共振表征，并注意到 CT 的相干时间高达 16 μs。我们在硼硅酸盐和铝硅酸盐玻璃中发现了零磁场下的 CT 行为，但在各种缺乏硼或铝的二氧化硅玻璃中没有。退火可减少或消除零场信号。由于硼和铝具有相同的价态，并且在取代硅时是受体，因此我们认为观察到的 CT 行为可能是由硼硅酸盐玻璃内的自旋 1 硼空位中心产生的，同样，铝硅酸盐玻璃中的铝空位中心也产生。