Cavity quantum electrodynamics with a single molecule: Purcell enhancement, strong coupling and single-photon nonlinearity

Control of light–matter coupling at the quantum level is an enabling technique for many emerging quantum technologies. This tutorial describes recent advances in achieving efficient coupling of light with a single molecule using an optical Fabry–Perot microcavity. We demonstrate that the efficient cavity-molecule coupling converts the molecule to an effective two-level system. In this regime, a single molecule can act as a nearly perfect reflecting mirror and exhibits optical nonlinearity at the ultimate level of single photons. (tutorial)