Quantum beats and wave mixing interactions in Raman systems: multimode squeezed and entangled states

Abstract

We describe the effects of Raman interactions on the quantum correlations of multimode optical fields. It is shown that both quantum beats and four-wave mixing processes exist in the Raman interactions of multimode fields with atomic reservoirs. These two mechanisms combine to lead to emission in pairs into multiple cavity modes. For four fields taken as examples, we find that the four-mode squeezed state can be created at steady state. From this we can obtain the Greenberger–Horne–Zeilinger entangled state, and the linear and square cluster entangled states. This scheme does not need the preparation of the initial states of atoms and cavity modes, and is robust against atomic spontaneous decay.