Characterization of Group-IV Color Center Hyperfine Coupling for Brokered Entanglement Protocols

A quantum register coupled to a spin-photon interface is a key component in brokered entanglement protocols for quantum communication and information processing. Group-IV color centers in diamond (SiV, GeV, and SnV) are promising candidates for this application, comprising an electronic spin with optical transitions acting as a spin-photon interface. However, the use of the intrinsic group-IV nuclear spin as a quantum register for brokered entanglement remains an outstanding challenge, particularly for the heavier elements, GeV and SnV, whose hyperfine features have not been extensively studied. Here, we present first-principles and experimental results characterising the hyperfine properties of the group-IV color centers. We show that the SnV has an optically resolvable hyperfine structure due to electron-nuclear coupling which is an order of magnitude larger than the lifetime-limited linewidth of the optical transition. We discuss how this structure changes under bias conditions, and how the hyperfine levels can be used in brokered entanglement protocols.