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

TL;DR

This paper demonstrates a fully optical method for controlling a solid-state NV center spin in diamond, enabling initialization, manipulation, and readout without microwave techniques, thus simplifying quantum control protocols.

Contribution

The authors introduce an all-optical approach to control NV center spins using coherent dark states, eliminating the need for intersystem crossing and microwave ESR techniques.

Findings

Achieved optical initialization, readout, and manipulation of NV center spins.

Performed measurements of spin coherence using purely optical methods.

Demonstrated control along arbitrary quantum bases with optical pulses.

Abstract

The study of individual quantum systems 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 quantum systems, these operations rely on disparate techniques that can vary widely depending on the 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 (ESR) 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 intersystem crossing. By tuning an NV 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 directly performed along any arbitrarily-chosen quantum basis, removing the need for extra control steps to map the spin to and from a 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 control within a smaller footprint and within photonic networks. Likewise, this approach obviates the need for both ESR manipulation and spin addressability through the intersystem crossing. This method could therefore be applied to a wide range of potential solid-state qubits, including those which currently lack a means to be addressed.