Quantum Network Nodes Based on Diamond Qubits with an Efficient Nanophotonic Interface
C. T. Nguyen, Денис Дмитриевич Сукачев, Mihir K. Bhaskar, Bartholomeus Machielse, David Levonian, Erik Knall, P. Stroganov, Ralf Riedinger, Hongkun Park, Marko Lončar, M. D. Lukin · Physical Review Letters · 2019
Quantum networks require functional nodes consisting of stationary registers with the capability of high-fidelity quantum processing and storage, which efficiently interface with photons propagating in an optical fiber. We report a significant step towards realization of such nodes using a diamond nanocavity with an embedded silicon-vacancy (SiV) color center and a proximal nuclear spin. Specifically, we show that efficient SiV-cavity coupling (with cooperativity C>30) provides a nearly deterministic interface between photons and the electron spin memory, featuring coherence times exceeding 1 ms. Employing coherent microwave control, we demonstrate heralded single photon storage in the long-lived spin memory as well as a universal control over a cavity-coupled two-qubit register consisting of a SiV and a proximal ^{13}C nuclear spin with nearly second-long coherence time, laying the groundwork for implementing quantum repeaters.