Progress Towards Quantum Repeater Nodes Using Silicon-Vacancy Centers in Diamond*

Quantum repeaters are a crucial component for long-range quantum networks, allowing network nodes to overcome photon loss by utilizing a long-lifetime quantum memory that can store quantum states across multiple node linking attempts. Silicon- vacancy (SiV) centers incorporated in diamond nanophotonic cavities have been shown to be a promising platform for quantum networking due to their efficient single-photon generation and spin-photon interface. In this work, we demonstrate the control of a weakly coupled ¹³C nuclear spin in this system, forming a two-qubit node with the SiV electron spin. We perform conditional gates between the electron and ¹³C spins, showing that each can be entangled independently with an incoming photon, and measure ¹³C coherence times exceeding 100 ms, even under repeated electron optical readout pulses. This long-lived memory capability, combined with the electron’s spin-photon interface, offers a route toward deterministic nonlocal gates and show ongoing attempts toward fully fledged quantum repeater protocols based on the SiV platform.