【作者】 赵宇靖；

【导师】 方细明；

【作者基本信息】 湖南师范大学 ， 原子与分子物理， 2014， 博士

【摘要】 量子信息学是量子力学与信息科学相结合的一门新兴交叉学科。目前能够进行量子信息处理和量子计算的物理系统主要有：腔量子电动力学、离子阱、核磁共振、超导约瑟夫森结、量子点和氮-空穴(N-V)中心系统等。在室温下,N-V中心系统具有良好的可控性和相当长的消相干时间,因此它被认为是实现量子信息处理和量子计算的很有前途的候选者之一。另一方面,电流偏置的约瑟夫森结(CBJJ)超导量子比特具有很好的可集成性和相干性,因此得到了广泛的研究。N-V中心系统与超导量子比特系统以及传输线共振子(TLR)等都有很好的耦合,而且其处理方法与原子系统以及超导系统有很多相似之处,因此N-V中心、CBJJ、TLR三者相耦合的复合量子系统成为本论文研究的重点。本论文的目的是基于上述复合量子系统及当前的实验技术水平,研究量子信息的存储与取回,纠缠态的制备,单向量子计算的实现,量子逻辑门以及量子克隆机的实现。本论文共分为六章。第一章为绪论,首先简要介绍了本文的研究背景与现状。另外,介绍了本论文中要用到的几个物理体系和基本概念：N-V中心系统、约瑟夫森效应、超导相位量子比特、超导传输线的量子化以及电路量子电动力学的基本理论。第二章,我们首先设计了一个利用复合量子系统实现将单量子比特信息存入量子记忆单元以及将此量子比特信息从量子记忆单元中取回的方案,然后将此方案扩展到两个量子比特以及N个量子比特的情况,最后利用量子主方程的方法计算了此方案的传输保真度。由于在此方案中的N个TLR处于虚激发状态,因此极大地降低了TLR的实验要求。并且由于TLR、N-V中心及CBJJ的相干时间足够长,因此在此系统中能够实现高保真度的量子信息的存储与取回。第三章,我们利用一个复合量子系统中的三种相互作用哈密顿量制备了N量子比特GHZ纠缠态。此系统中仅仅包含1个可以调节的CBJJ量子比特和N个N-V中心量子比特,并且CBJJ和TLR以及N-V中心和TLR之间的相互作用能够通过调节CBJJ的外部参数以及每个TLR的频率而被独立地打开和关闭,因此能够容易的获得三种相互作用哈密顿量。由于在整个操作过程中不需要调节N-V中心量子比特的能级间隔,因此操作得到了极大地简化。并且此方案中的操作时间和N-V中心量子比特数无关,因此操作时间不会随量子比特数的增加而增加。第四章,我们首先在一个复合固态量子系统中制备了N量子比特线性团簇态,然后通过连接两条线性团簇态而扩展成了一个更大的一维和二维团簇态,最后利用这两种团簇态证明了量子计算的两种操作。在这一系统中,通过交换虚光子和消去失谐模可以有效地抑制TLR和CBJJ的激发,这极大地减少了TLR和CBJJ的实验要求。通过调节TLR的频率和CBJJ的能级分裂问隔,可以有效地打开和关闭N-V中心-TLR之间以及CBJJ-TLR之间的相互作用,因而此方案非常容易控制。并且在此系统中所使用的固态量子比特具有非常好的稳定性和可扩展性。第五章,我们设计了一个基于复合固态量子系统实现1→2通用量子克隆机的方案。在我们的系统中不存在飞行量子比特,并且通过调整CBJJ的外部参数和每一个TLR的频率可以使得CBJJ-TLR(?)NV-TLR相互作用类似于开关中的“开／关”功能。在我们的设计方案中,仅仅需要一个控制非门和四个CBJJ-NV相互作用,并且在最后辅助态中只有三个量子比特,这就使得此系统中的克隆转换作用简单多了。第六章,是对本文工作的总结和对未来工作的展望。更多还原

【Abstract】 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 the1→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.更多还原