Research On Entanglement Properties Of The System Consisting Of Superconducting Qubits Coupled To Nitrogen-Vacancy-Center Ensemble In Diamond

As an important physical resource,quantum entanglement plays a very important role in the field of quantum computing,quantum storage and quantum communication.In many quantum systems,the nitrogen-vacancy-center ensemble(NVE)and superconducting qubits have attracted much attention due to their good maneuverability,flexibility and integration.Based on the important application of the NVE and superconducting qubits in quantum information,this thesis mainly focuses on the entanglement properties of the system consisting of superconducting qubits coupled to nitrogen-vacancy-center ensemble in diamond.The detailed contents are as follows:We have studied properties of entanglement between two flux qubits and and a NVE.The influence of the initial entanglement degree of the flux qubit C,the coupling strength between two flux qubits,the coupling strength between the flux qubit M and the NVE on the bipartite entanglement and the tripartite entanglement are discussed.The maximum entanglement state between two flux qubits is explained by the quantum coherence theory.The influence of the dissipation factor of two flux qubits on the entanglement in the presence of dissipation is discussed.A system composed of two superconducting qubits and two NV ensembles is studied.The effects of the initial entanglement degree of two NVEs,the coupling strength between the superconducting qubit and the NVE,the coupling strength between two superconducting qubits,the dissipation factor on the bipartite entanglement and the tripartite entanglement are discussed by the concurrence and three-tangle in the ideal case and in the presence of dissipation.This proposal may provide a way to control and manipulate the entanglement in the theory.