Generation Of Entanglement States And Its Applications Based On Cavity QED And NV Centers

Quantum information, which is the combinative product of quantum mechanics and information science, is a very promising new research field. A lot of research has been done and a lot of progress has been made both theoretically and experimentally. In the field of quantum information, quantum entanglement always plays a princi-pal role and is used widely as indispensable resource for the application of quantum information science. At present, there are many potential physical candidates for quantum information processing such as ion traps, cavity QED, nuclear magnetic resonance, quantum dots, superconducting Josephson junction, NV centers in di-amond and so on. Due to the experimental difficulties, it is very hard to predict which one is the best. Ion traps, cavity QED, nuclear magnetic resonance might be mature but not scalable at present. Quantum dots, superconducting Josephson junction, NV centers are developed slowly, but they are the hope of scalable quantum information processing. The aim of this dissertation is to design simple schemes for the preparation of quantum entangled states, implementation of quantum logic gates and its applications with various physical systems based on the present experimental technology.In cavity QED system, the main contents are as follows:1) In optical cavity part, potential quantum gating have been proposed in the atoms confined in low-Q cavities, by single-photon input-output process. Different from the case of high-Q and strong coupling cavities, universal quantum gates have been accomplished for the atoms based on Faraday rotations. Through sending a single photon into cavities repetitively, multi-qubit CPF gates on local and non-local atoms as well as on DFS encoded qubits are available. By employing an auxiliary cavity, we can also accomplish universal quantum gates and obtain some relative applications in low-Q cavities cases.2) In microwave cavity part, we propose a scheme to teleport an arbitrary multi-particle two-level atomic state between two parties or an arbitrary zero- and one-photon entangled state of multi-mode between two high-Q cavities in cavity QED. The scheme is based on the resonant interaction between atom and cavity and does not involve Bell-state measurement.The main contents concerned in NV centers:1) We propose a practical scheme for constructing cluster states among nuclear spins in nitrogen-vacancy defect centers (NV centers) in different diamonds. The entanglement of nuclear spins within a NV center is made by hyperfine coupling via electron spin and the entanglement between remote NV centers accomplished using parity projection of the emitted photons.1) We also provide a potential scheme to entangle distant negatively charged nitrogen-vacancy (NV) centers using nanomechanical resonators (NAMRs) and a common superconducting interference device (SQUID). Via virtually exciting the vibrational mode of the NAMRs, we show the effective coupling between the NV centers and the SQUID.Finally, we will conclude with a summary of our work and an outlook for possible future research.