The Rabi cycle is a term from the field of quantum optics.

When an atom (or some other two-level system) is illuminated by a coherent beam of photons, it will cyclically absorb photon and re-emit them by stimulated emission. One such cycle is called a Rabi cycle and the inverse of its duration the Rabi frequency of the photon beam.

This mechanism is fundamental to quantum optics. It can be modelled using the Jaynes-Cummings model and the Bloch vector formalism.

The name is in reference to Isidor Isaac Rabi.