Generating Entanglement And Realizing Logic Gate In Hybrid Solid Quantum System

Quantum information is emerging, in the1980s. This subject promotes the revolution of informatics. The generation of quantum entanglement and realizing quantum logic are important subjects in quantum information field. Entanglement is not only a characteris-tic to distinguish between the classical physics and quantum physics, but also a is useful resource in the quantum informatics. And quantum logic operations are essential body in quantum information processing. Therefore, the study of both quantum entanglement and quantum logic are valuable. On the other hand, the information needs a carrier which is a realistic physical system. Recently, with the rapid development of nanotechnology and superconductivity technology, solid physical systems of superconducting Josephson junction devices have controllability and integratability, and nitrogen-vacancy (NV) center has long coherence time, become most promising candidates for carrying information. So, we focus on study of generation of entangled states and realizing quantum logic gate in solid system in this thesis. The dissertation has been divided into six chapters, and our works are included in the chapters from3to6.In Chapter1, we introduce the background and the significance of the study, as well as the historical overview of general qubits is expounded. At the end of this chapter, the organization of the thesis is given.In Chapter2, the fundamental concept and theories of quantum information are intro-duced, including qubit, entangled state, fidelity, quantum gate. Then, the circuit-QED system and a mathematical method are introduced.In Chapter3, we focus on studing quantum information processing with solid supercon-ducting qubit. Firstly, a scheme is proposed to generate two-qubit maximal entangled state only requiring one-step operation, via two rf-SQUIDs coupling. Then, the influence of the dephasing and relaxation of qubit on the generation of entanglement is discussed. Also, the information exchange can be realized in this protocol. Second, generation of three kinds of multi-qubits entangled states (Cluster state, GHZ sate and W sate) of many low-decoherence flux qubits coupling with transmission line resonator are investigated. At last, a quantum net is constructed using superconducting quantum system. Through analysing information processing unit, the entanglement of random two-qubit in adjacent cavity is prepared. And high-fidelity information transmission can be realized in this system.In Chapter4, the generation of entanglement is studied in two superconducting cavities. Two cavities can be induced coupling via a CBJJ acts as a tunable coupler. The odd (even) entangled coherent states are prepared. Then the influence of cavities decay on the prepared entangled states is analysed.In Chapters, a quantum memory device, which has long coherence time, is proposed in hybrid solid quantum system. Under the large detunning condition, via a nanoinechanical resonator inducing the coupling between NV center and charge qubit, the information can be stable stored in NV center owing to that has long coherence time.In the last Chapter, we develop a theoretical scheme for creating coupling between NV ensemble and superconducting qubit. Through adjusting local external flux threading the superconducting qubit loop, a flexible two-qubit controlled phase gate that one controlling qubit controls random target qubit is realized. In addition, the influence of the decay of system excited states on the realizing quantum gate is discussed.Finally, the conclusions and discussion are given.