  Deterministic coupling of single solid-state emitters to nanocavities is the
key for integrated quantum information devices. We here fabricate a photonic
crystal cavity around a preselected single silicon-vacancy color center in
diamond and demonstrate modification of the emitters internal population
dynamics and radiative quantum efficiency. The controlled, room-temperature
cavity coupling gives rise to a resonant Purcell enhancement of the zero-phonon
transition by a factor of 19, coming along with a 2.5-fold reduction of the
emitter's lifetime.
