Researchers can reduce the noise level in the amplitude or phase or a light beam by controlling its interaction with a mechanical oscillator in a mirrored cavity. In this simplified schematic of Purdy et al.’s experiment, a coherent light beam (with equal noise in the amplitude and phase) enters a mirrored cavity and exerts radiation pressure on a membrane, exciting vibrations. The vibrating membrane changes the resonant frequency of the light in the cavity, and therefore, the light’s phase. Purdy et al. controlled this interaction to reduce (squeeze) the noise level in the amplitude or phase of the emitted light beam.