| As an available "resource", quantum entanglement has been widely applied to quantum computing, quantum key distribution and quantum communication, etc. Theoretical and experimental research for quantum entanglement has become an important subject in quantum information science. In recent years, many quantum systems have been proposed to prepare the entangled state, such as ions, electronic spin, photon, quantum dots in semiconductor and cavity quantum electrodynam-ics (QED) systems. Decoherence effects caused by the inescapable interaction between system and environment greatly restrict the preparation of entangled s-tates and realization of the corresponding quantum information processing (QIP) schemes. In the aspect of suppression decoherence, cavity QED systems have in-comparable advantages and become an ideal platform in preparation, storage and control entangled states and realization of the QIP. This thesis research the prepa-ration of entangled states and entanglement dynamics in cavity QED systems. The main content is as follows:1. We investigate the entanglement generation between two nitrogen-vacancy (NV) centers in diamond nanocrystal coupled to a high-Q whispering-gallery modes (WGMs) microtoroidal resonator and look into entanglement dynamics. The influences of the coupling strength between the WGMs, the distance between two NV centers, the frequency detuning between the NV center and microres-onator, and the initial state of the system on the dynamics of concurrence are dis-cussed. It is found that the maximum entanglement between the two NV centers can be created by properly adjusting these controllable system parameters.2. We propose a theoretical scheme to generate maximum entanglement be-tween two dipole emitters coupled with a WGM microtoroidal cavity. The cou- pling strengths between the dipole emitters and the microcavity have been substan-tially enhanced owing to the help of the metal nanoparticles (MNPs). We obtain the maximum entanglement between the two dipole emitters in this cavity QED system. We also discuss the influence of the coupling strength, the initial state and the detuning on the entanglement.3. Based on the quantum Zeno effect, we propose a theoretical scheme to achieve three-dimensional (3D) entanglement between two distant five-level atom-s. In our scheme, the two atoms are trapped individually in two spatially-separated double-mode cavities connected by an optical fiber. Using the effective quantum Zeno dynamics, only one step operation is required to deterministically create the3D entangled state with high fidelity. Moreover, the numerical simulations clearly show that the proposed scheme is robust against the deviation of the system pa-rameters and insensitive to various decoherence factors. We justify our scheme by considering the experimental feasibility within the currently available technology.4. We propose a scheme for generation the entanglement between two sepa-rate NV centers in diamond nanocrystal coupled to a photonic molecule consisting of a pair of coupled photonic crystal (PC) cavities. It is found that, the entan-glement dynamics strongly depends on the cavity-cavity hopping strength and the NV-center-cavity detuning. High entanglement peak and long-lived entanglement plateau can be achieved by properly adjusting these system parameters. Our results may be useful for real experiments in a PC platform.5. We investigate the photon-photon entanglement in a hybrid optical sys-tem composed of a single diamond NV center coupled to a photonic molecule. The nitrogen-vacancy (NV) center embedded in one PC cavity. It is shown that, by properly adjusting the system parameters including the cavity-cavity hopping strength, the NV center-cavity detuning, and the detuning between the two bare cavity modes, the long-time stable photon-photon entanglement can be realized. This thesis not only deepens our awareness and understanding of entangled states and entanglement dynamics, but also provides a new way to prepare stable entangled states. Moreover, our research may have help for realizing QIP schemes. |
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