| The study on the generation and application of nonclassical optical fields is an international advanced research topic. Up to now, many kinds of nonclassical states including entanglement states have been obtained in theory and experiments respectively. For example: 1, quadrature amplitude (or phase) squeezed light; 2, quantum correlation twin beam; 3, sub-poissonian light (or intensity squeezed light). Actually, the continuous variable entanglement is correlative with squeezing. It is verified that EPR correlations exist in the quadrature-phase amplitudes of the signal and idler beams generated by a subthreshold optical parametric oscillator. But the two coupled modes by projecting the signal and idler fields along polarization direction at ±45° are squeezed states.Nonclassical optical fields play an important role in quantum measurement and quantum communication. They have been widely used in optical precision measurement below shot-noise-limit, quantum non-demolition measurement, quantum teleportation, quantum dense coding and quantum cryptography etc. Entanglement between more than two parts is the essential base for developing quantum communication networks. The quantum teleportation network, telecloning, controlled dense coding and so on can be realized with the multipartite entanglement.This thesis introduces the experimental realization of preparing sub -poissonian light with twin beams and the theoretical investigation on the generation of continuous variable tripartite entanglement using cascaded nonlinearities. The specific contents are divided into three parts:1. The operation principle of doubly resonant Nondegenerate Optical Parametric Oscillator (NOPO) above threshold is described. The dependences of the twin beams quantum noise on the cavity parameters are analyzed.2. The experimental principle and setup for preparation of sub-poissonian light with twin beams are introduced. And the result and analysis are reported. |
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