Applications Of N-V Centers In Quantum Information Processing And Quantum Computation

Quantum information science is the new related areas of quantum mechan-ics and information science. At present, the physical systems which could real-ize the quantum information processing and quantum computing are:cavity-QED, ion trap, nuclear magnetic resonance, superconducting Josephson junc-tion, quantum dot, nitrogen-vacancy (N-V) center and so on. The N-V center system has well controllability and long decoherence time at room temperature, so it becomes one of the most promising candidates in quantum information processing and quantum computing. On the other hand, the current-biased Josephson-junction (CBJJ) superconducting qubit is easily integrated and have long coherence time, so it has been studied extensively. The N-V center sys-tem is well coupled to superconducting qubit system and transmission line resonator (TLR), and the research method is very similar to the atom system and superconducting system, therefore, the hybrid quantum system which con-tains the N-V center, CBJJ, and TLR becomes the research emphasis of this dissertation. The aim of this dissertation is to study the quantum information storage and retrieval, the preparation of entangled states, the implementation of one-way quantum computing, the implementation of quantum logic gates and quantum cloning machine based on the above hybrid quantum system and current experimental technology.The dissertation consists of six chapters. In the first chapter, we give a brief introduction about the research background and the present situation. In addition, we introduce the basic theory of several physics systems in this dissertation, such as N-V center system, superconducting Josephson junction, transmission line resonator, and circuit-QED.In the second chapter, we first design a scheme for realizing one-qubit information storage (retrieval) into (from) quantum memory by using a hy-brid quantum system, then we extend this scheme to the case of two-qubit information and N-qubit information, and last we calculate the fidelity of the transfer process by using the quantum master equation. The scheme only in-volves virtual excitation of the TLRs, this greatly reduces the experimental requirement of the TLRs. Since the lifetime of the TLRs, CBJJs, and N-V centers are long enough, the quantum information storage and retrieval could be achieved with a very high fidelity in the system.In the third chapter, we prepare the N-qubit GHZ entangled state by using three kinds of interaction hamiltonian in a hybrid quantum system. This system only involves one tunable CBJJ qubit and N N-V center qubits, the CBJJ-TLR and NV-TLR interactions could be switched on and off by tuning the external parameters of the CBJJ and the frequency of each TLR, so the three kinds of interaction Hamiltonian could be obtained easily. Because of no need to adjust the level spacings of the N-V centers during the whole process, so the operation is very simple. The operation time in this scheme is independent of the number of the N-V center qubits, so it does not increase with the number of qubits.In the fourth chapter, we first prepare the N-qubit linear cluster state with a hybrid solid-state quantum system, then we prepare the two-dimensional cluster state by connecting two pieces of linear cluster states, and last we demonstrate the two operations of quantum computing with the two kinds of cluster states. In this system, the excitations of the TLRs and CBJJ are suppressed by exchanging the virtual photons and eliminating the detuning modes, this greatly reduces the experimental requirement of the TLRs and CBJJ. The NV-TLR and the CBJJ-TLR interactions can be switched on/off easily by tuning the frequency of the TLRs and the level splitting of the CBJJ, therefore, this scheme is very easily to be controlled. And the solid-state qubits in our system have very good stability and scalability.In the fifth chapter, we design a scheme to realize the1â†'2universal quantum cloning machine with a hybrid solid-state quantum system. In our system, there are no flying qubits, and the CBJJ-TLR and NV-TLR interac-tions could be switched on/off by tuning the external parameters of the CBJJ and the frequency of each TLR. In addition, only one controlled-NOT gate operation, four CBJJ-NV interactions, and three qubits in the ancilla’s final state in our system, therefore, the implementation of quantum cloning is much simplified.In the sixth chapter, we give a brief summary of the work and a outlook of the future work.