Abstract

The first realisations of interferometers for neutral atoms, which have only recently been achieved,^[1] make it desirable to invent methods of preparation of the transverse position profile of cooled atomic beams. Here we study the collapse of the atomic position distribution that is induced by measurements on cavity fields the atom has been interacting with. The measurement probe is a high quality cavity with a standing light wave, or a sequence of cavities, pre- pendicular to the atomic beam. The transverse momentum transfer of the atom-light interaction is such that the quadrature component of the electromagnetic field in the cavity carries information on the position of the atom. The requirement for the coupling between the atom and the light field to be of QND type are that the interaction time of the atom with the standing wave is sufficiently short for dispersion of the atomic wave packet to be negligible, i. e. we must assume the Kapitza-Dirac limit, and that the atom remains essentially in the ground state, which requires far-offresonant detunings. Under these conditions cavity field measurements contain information on the transverse atomic center of mass position, i. e. their outcome depends on where within the standing wave the atom crosses the cavity. We investigate such correlations of the quadrature phase of the cavity field and the atomic position by means of joint and conditional probability densities.

© 1992 IQEC