  Silicon carbide has recently been developed as a platform for optically
addressable spin defects. In particular, the neutral divacancy in the 4H
polytype displays an optically addressable spin-1 ground state and
near-infrared optical emission. Here, we present the Purcell enhancement of a
single neutral divacancy coupled to a photonic crystal cavity. We utilize a
combination of nanolithographic techniques and a dopant-selective
photoelectrochemical etch to produce suspended cavities with quality factors
exceeding 5,000. Subsequent coupling to a single divacancy leads to a Purcell
factor of ~50, which manifests as increased photoluminescence into the
zero-phonon line and a shortened excited-state lifetime. Additionally, we
measure coherent control of the divacancy ground state spin inside the cavity
nanostructure and demonstrate extended coherence through dynamical decoupling.
This spin-cavity system represents an advance towards scalable long-distance
entanglement protocols using silicon carbide that require the interference of
indistinguishable photons from spatially separated single qubits.
