Control of multi-qubit nodes for diamond quantum networks

Quantum networks consisting of multiple connected nodes enable distributed quantum computation and secure quantum communication. Such networks require multi-qubit quantum registers that can be remotely linked. In this work we demonstrate initialization and control of multiple qubits in a nitrogen-vacancy (NV) node in diamond. We use the NV electron spin as an ancillary qubit to detect individual weakly coupled nuclear carbon-13 spins and construct high-fidelity quantum gates [1]. With these gates we show initialization, control and entanglement of multiple nuclear spins. Combined with projective measurements of the NV electron spin [2] and long-range entanglement through optical channels [3] at cryogenic temperatures, this work paves the way for communication between distant quantum nodes via ancillary qubits while preserving complex entangled states in quantum memories within the nodes. \\[4pt] [1] T.H. Taminiau et al., Nature Nanotech. 9, 171 (2014)\\[0pt] [2] L. Robledo et al., Nature 477, 547 (2011)\\[0pt] [3] W. Pfaff et al., Science 345, 532-535 (2014)