QUANTUM LIMIT FOR THE ATOM-LIGHT INTERFEROMETER

The standard quantum limit is calculated for the atom-light interferom eter. It is shown that the smallest detectable phase is delta phi(min) = 1/2[N-atoms + 4N(photons))/NatomsNphotons](1/2). Therefore, in prac tical experiments, the accuracy is limited by the square root of the n umber of atoms. We propose a novel correlated atom-photon state interf erometer which makes a transition to the Heisenberg limit, delta phi(m in), proportional to 1/N-atoms, as the atoms approach a Bose condensat e. Such an interferometer may serve as a sensitive probe of the onset of Bose condensation. Finally, we point out that the correlated atom-p hoton state preparation scheme we propose may be used in a different w ay to approach the Heisenberg limit for non-Bose-condensed atoms.