Entanglement Property Of Continuous Variable Two-mode Light-field In A Nondegenerate Four-wave Mixing System

In addition to being of fundamental interest in quantum mechanics, entanglement as quantum correlations among quantum systems is a key element in rapid developing quantum informatics. Now, continuous variable entanglement has attracted a lot of attention in quantum optics and quantum information due to the experimental realization of quantum information processings in continuous variable regime. Any attempt to exploit the entanglement have to, however, face the corruption of the entanglement by unavoidable decoherence. As a result, how to produce the robust, steady, and high entanglement is an interesting research issue. In this thesis, we focus mainly on the preparation of bright and high continuous variable entanglement.We apply nondegenerate four-wave mixing processes to the generation of stable continuous variable entangled light and study the evolution of continuous variable entangled light with time. We analytically get the characteristic function of the two-mode field and find that the system is an optical parametric amplifier. We also show that the two-mode cavity field exhibits stable continuous variable entanglement under some conditions. The degree of the entanglement is dependent upon the two photon intensity I₂ , the coopera-tivity parameter C and the side-mode detuningâ–³'.Next, We have investigated a double-ladder atom trapped in a non-degenerate doubly resonant cavity. We obtain the master equation of the cavity modes and consider further the dynamics of this physical system under suitable conditions. It is found that employing these conditions the physical system is a nondegenerate parametric oscillatorin in NDFWM. the large detuning A is necessary for improving squeezing and entanglement. In order to get bright and strong entangled field, the system should operate above threshold.