When a photon is reflected by a mir

When a photon is reflected by a mirror, a back-action force is exerted onto it. Owing to the quantum nature of light, the number of the photons hitting the mirror fluctuates, and thus the back-action force fluctuates, resulting in displacement noise of the mirror. The noise caused by this fluctuation is called the radiation pressure noise.The fluctuating force level is proportional to the square root of the laser power √ P .Since the photocurrent shot noise is proportional to 1/ √ P , there is a trade-off between the shot noise and the radiation pressure noise. There is a limit on the sensitivity of an interferometer called the standard quantum limit (SQL), which corresponds to the quantum mechanical limit of the measurement from the Heisenberg uncertainty principle. Currently various methods to beat this limit are proposed [23].