Solid-state quantum emitters such as the N-
V center in diamond have applications ranging from single-photon sources to quantum sensors, with some quantum properties preserved even under ambient conditions. A central challenge is to access these quantum properties efficiently, by catching as much emitted light as possible. In this study a tunable optical microcavity, with a mode volume as small as one wavelength cubed, is used to enhance spontaneous emission of single N-
V centers in diamond, via the Purcell effect. This allows the authors to extract large amounts of light from several individually addressable emitters, and to control their spontaneous-emission rate.