Entanglement of dark electron-nuclear spin defects in diamond

A promising approach for multi-qubit quantum registers is to use optically addressable spins to control “dark” electron-spin defects in their environment. While recent experiments have observed signatures of coherent interactions with such “dark” spins, it is an open challenge to realize the individual control required for quantum information processing. Here we demonstrate the initialization, control and entanglement of individual P1 centers that are part of a spin bath surrounding a nitrogen-vacancy center in diamond. We realize projective measurements to prepare the P1’s multiple degrees of freedom - its Jahn-Teller axis, nuclear spin and charge state - and exploit these to isolate and access multiple P1s in the bath. We develop control and single-shot readout of the nuclear and electron spin, and use this to demonstrate an entangled state of two P1 centers. These results provide a proof-of-principle towards using dark electron-nuclear spin defects as qubit registers for quantum sensing, computation and networks.