Solid-state electronic spins are extensively studied in quantum information science, as their large magnetic moments offer fast operations for computing¹ and communication^2,3,4, and high sensitivity for sensing⁵. However, electronic spins are more sensitive to magnetic noise, but engineering of their spectroscopic properties, for example, using clock transitions and isotopic engineering, can yield remarkable spin coherence times, as for electronic spins in GaAs⁶, donors in silicon^7,8,9,10,11 and vacancy centres in diamond^12,13. Here we demonstrate simultaneously induced clock transitions for both microwave and optical domains in an isotopically purified ¹⁷¹Yb³⁺:Y₂SiO₅ crystal, reaching coherence times of greater than 100 μs and 1 ms in the optical and microwave domains, respectively. This effect is due to the highly anisotropic hyperfine interaction, which makes each electronic–nuclear state an entangled Bell state. Our results underline the potential of ¹⁷¹Yb³⁺:Y₂SiO₅ for quantum processing applications relying on both optical and spin manipulation, such as optical quantum memories^4,14, microwave-to-optical quantum transducers^15,16, and single-spin detection¹⁷, while they should also be observable in a range of different materials with anisotropic hyperfine interactions.

固态电子自旋在量子信息科学中得到了广泛的研究，因为它们的大磁矩为计算¹和通信^2、3、4提供了快速的操作，并为传感^5提供了高灵敏度。但是，电子自旋对磁噪声更敏感，但是对它们的光谱特性进行工程设计（例如使用时钟跃迁和同位素工程）会产生显着的自旋相干时间，例如GaAs ^6中的电子自旋，硅^{7,8， 9,10,11}和钻石^12,13中的空缺中心。在这里，我们展示了在同位素纯化的^171中微波和光学域同时引起的时钟跃迁Yb ³⁺：Y ₂ SiO ₅晶体，在光域和微波域的相干时间分别大于100μs和1 ms。这种效应是由于高度各向异性的超精细相互作用，使每个电子-核态成为纠缠的贝尔态。我们的结果强调了¹⁷¹ Yb ³⁺：Y ₂ SiO ₅在依赖于光学和自旋操纵的量子处理应用中的潜力，例如光学量子存储器^4,14，微波至光学量子换能器^15,16和单量子阱。旋转检测¹⁷，但在具有各向异性超精细相互作用的各种不同材料中也应观察到它们。