All-optical control of a solid-state spin using coherent dark states

Abstract

The study of individual quantumsystems in solids, for use as quantum bits (qubits) and probes of decoherence, requires protocols for their initialization, unitary manipulation, and readout. In many solid-state quantumsystems, these operations rely on disparate techniques that can varywidely dependingonthe particular qubit structure.One such qubit, the nitrogen-vacancy (NV) center spin in diamond, can be initialized and read out through its special spin-selective intersystem crossing, while microwave electron spin resonance techniques provide unitary spin rotations. Instead, we demonstrate an alternative, fully optical approach to these control protocols in an NV center that does not rely on its intersystemcrossing. By tuning anNV center to an excited-state spin anticrossing at cryogenic temperatures, we use coherent population trapping and stimulated Raman techniques to realize initialization, readout, and unitary manipulation of a single spin. Each of these techniques can be performed directly along any arbitrarily chosen quantumbasis, removing the need for extra control steps tomap the spin to and froma preferred basis. Combining these protocols, we perform measurements of the NV center's spin coherence, a demonstration of this full optical control. Consisting solely of optical pulses, these techniques enable controlwithin a smaller footprint and within photonic networks. Likewise, this unified approach obviates the need for both electron spin resonancemanipulation and spin addressability through the intersystem crossing. This method could therefore be applied to a wide range of potential solid-state qubits, including thosewhich currently lack ameans to be addressed.