Generation Of Continuous-Variable Entanglements And Conditional Cloning

Quantum entanglement is something that even Einstein had a little difficulty with, and quantum entanglement is an area of science that will one day dominate the way we look at information, the way we communicate secretly and the way our computers do their thing. In the future quantum information, the important work is generation of entanglement and the application. The entanglement can used in future quantum information technology, such as quantum cryptography, controlled dense coding, teleportation, and quantum computation. The spatial multimode entanglement can be used to improve image quality, furthermore the multipartite entangled light with different frequencies could aid the linking together of two optical systems at different wavelengths and particular bridging in optical frequency between telecommunication windows and the prominent multi-level atomic systems used in quantum memories and information processing.In this thesis, we mainly investigate the research works about the continuous variables quantum entanglement as follows:1. To generate the entanglement, the fine laser as resouce is necessary. We firstly suppressed noise of fiber laser by two methods:opt-electronic feed-forward and mode cleaner, as the result, the noise of fiber laser reach shot noise limit after3MHz, the maximum noise suppression is27dB.2. We experimentally demonstrated two pairs of entanglements of Hermit-Gauss modes (HG01entangled states and HG10entangled states) are generated simultaneously in one type-II OPA, the HG01entangled states is bright field, and the HG10entangled states is dark filed. The variance of HG01entangled states is3.44, and the variance of HG10entangled states is3.34. The type of entanglement is also continuous-variable hyper-entanglement in polarization and orbital angular momentum; it can be applied into the fields of quantum information. Basing on the experiment, we also have generated four modes cluster entanglement among high order modes.3. We introduced and studied the type-â…¡ second order nonlinear interaction between two fundamental fields and harmonic field in OPO and SHG, and demonstrated the reason of extra phase noise in experiment and guide a way for next experiment. In the theory, we demonstrated that the maximal tripartite entanglement produced neither by pure SHG nor OPO, but rather by an intermediate process which is optical parameter deamplifier with bright input of fundamental fields and harmonic field.4. We proposed an implementation of CV conditional cloning machine only using linear optical elements such as beam splitters, homodyne detection, and condition selection, no the nonlinear process (squeeze gate) and extra EPR. The cloning states can still be entangled states when fidelity beyond the4/9limit simultaneously. Due to the linear and high fidelity proposal, it is controllable and practicable in the present experimental situation and it can also be applied in the further quantum information process. The creative works are as follows:1. Experimentally suppressed noise of fiber laser.2. Experimentally simultaneously generated two pairs of high order mode entanglement in one OPA and four modes cluster entanglement among high order modes.3. Experimentally demonstrated the reason of extra phase noise in experiment and guide a way to generate muti-colour enatanglemeent in the next experiment. In theory, proposed a scheme of generation tripartite entanglement between two fundamental fields and harmonic field.4. Proposed an implementation of CV conditional cloning machine.