Solid-state devices for single-photon generation

General requirements for single-photon devices in various applications are presented and compared with experimental progress to date. The quantum information applications that currently appear the most promising require a matter qubit-enabled single-photon source, where the emitted photon state is linked to the state of a long-lived quantum system such as an electron spin. The nitrogen-vacancy center in diamond is a promising solid-state system for realizing such a device due to its long-lived electron spin coherence, optical addressability, and ability to couple to a manageable number of nuclear spins. This system is discussed in detail, and experimental results from our laboratory are shown. A critical component of such a device is an optical microcavity to enhance the coupling between the nitrogen-vacancy center and a single photon, and we discuss theoretically the requirements for achieving this enhancement.