Implementation Of Entanglement Analysis And Quantum Cloning Based On Input-Output Process Of Cavity

Quantum entanglement lies in the heart of quantum communication and var-ious computational tasks. So the research in quantum entanglement state prepa-ration and analysis has become the hot topic in recent years. Entanglement as an important resource has been widely applied in many aspects of quantum in-formation processing such as quantum cloning, which can evaluate the security of quantum cryptography. In this thesis, we present deterministic schemes for imple-menting multi-particle entanglement state generation and analysis, and quantum cloning via cavity input-output process. The main research contents as follows:(1)Atom and optical cavity coupled system:We propose the schemes to im-plement a nondestructive GHZ state analyzer with atoms and generate multi-atom entanglement state with high fidelity and entanglement degree in low-Q cavities by taking the coherent light as quantum channel. In the present schemes, we use horno-dyne detection for coherent light instead of traditional single-photon measurement duo to the higher success probability of the homodyne detection than single-photon measurement, we have also calculated the effect of atomic spontaneous emission on the fidelity and homodyne detection, and shown that the present scheme is not only robust in the condition of a bad cavity, but also feasible with current technology.(2)Quantum dot and optical cavity coupled system:We present a scheme to im-plement an optimal 1â†'2 economical phase-covariant quantum cloning machine with quantum dot spins in optical microcavities. By analyzing the fidelity of quantum cloning we confirm that it is robust against the dissipation caused by cavity decay, side leakage. For a strong coupling regime.the cloning fidelity approaches a stable optimal bound. Even in a weak coupling regime, it can also achieve a satisfactory high value and close to the optimal bound.(3)Nitrogen-vacancy(N-V) centers and microtoroidal resonators coupled sys-tem:Schemes for implementing optimal 1â†'2 universal, phase-covariant, and 1â†'M economical phase-covariant quantum cloning with N-V centers in diamond fixed on the exterior surface of a microtoroidal resonators, we also discuss the effect of dissi-pation and spectral diffusion in solid-state systems on cloning fidelity.The feasible analysis for above schemes shows, all of schemes can be realized with present experimental techniques, so they have very important value for the re-search of quantum information processing based on input-output process of cavity.