Measurement of Atomic Motion in a Standing Light Field by Homodyne Detection

It is shown that the photocurrent measured using homodyne detection of the phase quadrature on the output field of a cavity gives information about the transverse motion of an atom passing through the standing light field inside the cavity. Monte Carlo simulation techniques are used which result in quantum trajectories of the system conditioned on the measured photocurrent, i.e., the photocurrent defines the backaction of the continuous measurement on the atomic motion.