Hyperfine Spectroscopy of Isotopically Engineered Group-IV Color Centers in Diamond

A quantum register coupled to a spin-photon interface is a key component in quantum communication and information processing. Group-IV color centers in diamond ($\mathrm{Si}$${\mathrm{V}}^{-}$, $\mathrm{Ge}$${\mathrm{V}}^{-}$, and $\mathrm{Sn}$${\mathrm{V}}^{-}$) are promising candidates for this application, comprising an electronic spin with optical transitions coupled to a nuclear spin as the quantum register. However, the creation of a quantum register for these color centers with deterministic and strong coupling to the spin-photon interface remains challenging. Here, we make first-principles predictions of the hyperfine parameters of the group-IV color centers, which we verify experimentally with a comprehensive comparison between the spectra of spin active and spin neutral intrinsic dopant nuclei in single $\mathrm{Ge}$${\mathrm{V}}^{-}$ and $\mathrm{Sn}$${\mathrm{V}}^{-}$ emitters. In line with the theoretical predictions, detailed spectroscopy on large sample sizes reveals that hyperfine coupling causes a splitting of the optical transition of $\mathrm{Sn}$${\mathrm{V}}^{-}$ an order of magnitude larger than the optical line width and provides a magnetic field insensitive transition. This strong coupling provides access to a new regime for quantum registers in diamond color centers, opening avenues for novel spin-photon entanglement and quantum sensing schemes for these well-studied emitters.