Time-dependent electric field fluctuations at the subphoton level

Department of Physics and Astronomy, State University of New York, Stony Brook, New York 11794-3800~Received 27 May 2002; published 16 September 2002!We report studies of a third-order correlation function that records the conditional time evolution of the fieldof a fraction of a photon. We present results in the strong-coupling regime of cavity QED, where the detectionof a photon from the cavity prepares a state with a well-defined phase that evolves back to equilibrium via adamped vacuum Rabi oscillation. We perform a homodyne measurement conditioned on the photon detectionto observe the regression of the field amplitude. The measured field-photon correlation is nonclassical and canbe used to determine the spectrum of squeezing in an efficiency independent way.DOI: 10.1103/PhysRevA.66.033807 PACS number~s!: 42.50.Dv, 42.50.Ct, 32.80.2tI. INTRODUCTION