| Quantum information is a frontier subject that focuses on information encoding, transfer and processing via the coherence and entanglement of quantum systems. The electron spins of nitrogen-vacancy (NV) centers in a diamond have a long coherence time and can be easily manipulated by using the optical or microwave pulses. What’s more, for their nanoscale volume, NV centers can be coupled to various microcavities. Due to these advantages, the strong coupling between NV centers and nanocavities is considered to be an efficient way for constructing solid-state quantum information processors at a room temperature.In this thesis, based on the composite NV center-microcavity system, we propose a series of schemes for quantum information processing, which are robust against decoherence. The main contents are listed as follow.1. Based on quantum Zeno dynamics, we propose two schemes to realize the quantum state transfer between two NV centers with a single cavity and with a coupled-cavity system, respectively. Under the large detuning condition, the qubits are coupled through virtual photon exchange. Furthermore, the system dynamics is restricted within the subspace formed by the ground states of the qubits. These schemes were immune to both the loss of cavity and spontaneous emission of the qubits.2. We propose two schemes to realize two-qubit conditional phase gates in single cavity system based on resonant and off-resonant NV center-microcavity interactions, respectively. In the system comprised of two distant optical cavities connected by an optical fiber, we propose a scheme to realize unconventional geometric quantum phase gates with the help of a strong driving classical field. In this scheme, the phase gate operation is independent of the initial state of the cavity mode so that the fidelity is insensitive to thermal photons. Meanwhile, this gate has resistance to noise perturbation due to the advantage of geometric phase.3. We propose a scheme to control the entanglement between two NV center ensembles (NVEs) in the coupled NV center-superconducting cavity-circuit qubit system. Induced by the cavity mode and a classical field, NVEs interact with the circuit qubit. Through adjusting the frequency of the microwave field, the entanglement between the two NVEs can be controlled. We also propose schemes for preparation of NOON states, N-dimensional entangled states and entangled coherent states of two NVEs. In the whole process, the cavity mode is always in vacuum state, and hence the cavity decay is suppressed.4. We present a new scheme to generate W state of NV centers via adiabatic passage of the dark state. In this scheme, NV centers are coupled to distant optical cavities connected by an optical fiber. Meanwhile, we discuss the implementation of phase-covariant cloning. During the whole process, the system evolves in subspace of the dark state. The advantage of the scheme is that the fiber and the cavity modes are not excited during the dark state evolution. Furthermore, the interaction time does not need to be accurately controlled, and the fidelity is insensitive to fluctuations of the experimental parameters.5. We investigate the effects of a two-mode field on the entanglement dynamics of two NV centers. We consider two initially entangled NV centers, one of which interacts with a two-mode field in a Raman manner. We discuss the dependence of the concurrence evolution of these NV centers on the field photon numbers and the NV center-field coupling strength. |
