COLLECTIVE INTERACTION OF ATOMS AND LIGHT WITH CAVITY-ASSISTED RAMAN TRANSITIONS

Abstract

A cavity-assisted Raman transition between two atomic ground states is a two photon process induced by a strong laser beam together with a single mode of electromagnetic field supported by a high-finesse optical cavity. By coupling an ensemble of ⁸⁷Rb atoms to a high-finesse optical cavity and utilizing cavity-assisted Raman transitions, a spin-half Dicke model is simulated and phase transition thresholds are studied under different beam configurations. A theoretical model is developed to account for the effect of atomic motion on the critical coupling strength, which is in agreement with experimental results.

In an effective three-level system, the non-equilibrium phase transition of a spin-1 Dicke model is studied by tuning the ratio of coupling strengths between two cavity-assisted Raman transitions. Phase transitions and boundaries between normal, super-radiant and oscillatory phases are observed and obtained. This is the first simulation of a spin-1 Dicke model and observation of the oscillatory phase.

Making use of the high cooperativity and optical depth provided by our system, a heralded quantum memory scheme using a single photon is also studied. In our experiment, we are able to store a free-space single photon or a coherent pulse with a high heralding and retrieval efficiency.