DETECTION OF ATOMIC INTERFERENCE THROUGH COLLECTIVE RADIATION

We demonstrate a unique atomic interferometer employing collective rad iation from the atoms to measure the atomic phase. Atomic coherence is detected by interference of a continuous free-induction decay field a nd a continuous photon-echo field that originate in spatially separate d regions of an atomic beam. Using this system, we measure the 180 deg rees phase shift of a J = 0 atomic state that undergoes a 2 pi-rotatio n of the Bloch vector or a two-level optical transition.