High-Fidelity Quantum Memory for the Silicon-vacancy Defect in Diamond

Implementation of long range quantum networks requires network nodes with multiple interacting qubits which can be used to store and process information communicated via itinerant photons. We report significant progress towards deterministic realization of such nodes via the implantation of Silicon-29 ions into high quality factor diamond nanophotonic cavities. Silicon-vacancy color centers formed from these ions demonstrate strong interactions between the color center electron spin and the nuclear spin of the silicon atom, constituting a 2-qubit register. The constituent qubits and their interactions can be coherently controlled with microwave and RF signals sent using on-chip coplanar waveguides. We show the realization of high-fidelity gates including CNOT and SWAP gates between these long-lived quantum memories. By leveraging the efficient spin-photon interface enabled by the nanophotonic cavity this demonstration can be extended to a full implementation of the quantum repeater protocol.