We report on single electronic spins coupled to the motion of mechanical resonators by a novel mechanism based on crystal strain. Our device consists of single-crystal diamond cantilevers with embedded nitrogen-vacancy center spins. Using optically detected electron spin resonance, we determine the unknown spin-strain coupling constants and demonstrate that our system resides well within the resolved sideband regime. We realize coupling strengths exceeding 10 MHz under mechanical driving and show that our system has the potential to reach strong coupling. Our novel hybrid system forms a resource for future experiments on spin-based cantilever cooling and coherent spin-oscillator coupling.

The nitrogen-vacancy (NV) center in diamond has an optically addressable, highly coherent spin. However, a NV center even in high-quality single-crystalline material is a very poor source of single photons: Extraction out of the high-index diamond is inefficient, the emission of coherent photons represents just a few percent of the total emission, and the decay time is large. In principle, all three problems can be addressed with a resonant microcavity. In practice, it has proved difficult to implement this concept: Photonic engineering hinges on nanofabrication, yet it is notoriously difficult to process diamond without degrading the NV centers. Here, we present a microcavity scheme that uses minimally processed diamond, thereby preserving the high quality of the starting material and a tunable microcavity platform. We demonstrate a clear change in the lifetime for multiple individual NV centers on tuning both the cavity frequency and antinode position, a Purcell effect. The overall Purcell factor $F_P=2.0$ translates to a Purcell factor for the zero phonon line (ZPL) of $F_P^{\mathrm{ZPL}}\sim 30$ and an increase in the ZPL emission probability from about 3% to 46%. By making a step change in the NV’s optical properties in a deterministic way, these results pave the way for much enhanced spin-photon and spin-spin entanglement rates.