- We study the dynamics of the quantum optical spring, i.e., a spring whose spring constant undergoes discrete jumps depending on the quantum state of another system. We show the existence of revivals and fractional revivals in the quantum dynamics reminiscent of similar dynamical features in cavity QED. We recover in the semiclassical limit the results for an oscillator whose frequency undergoes a sudden change. The quantum optical spring is conceivable, for example, by a micromirror under the influence of radiation pressure by a field which is strictly quantum mechanical. Our work suggests that driven systems would in general exhibit a very different dynamics if the drive is replaced by a quantum source. 2008 The American Physical Society.