Realization of Three-Qubit Controlled-Phase Gate Operation with Atoms in Cavity QED System

We propose a scheme for realization of three-qubit controlled-phase gate via passing two three-level atoms through a high-Q optical cavity in a cavity QED system. In the presented protocol, the two stable ground states of the atoms act as the two controlling qubits and the zero- and one-photon Fock states of the cavity-field form the target qubit, and no auxiliary state or any measurement is required. The numerical simulation shows that the gate fidelities remain at a high level under the influence of the atomic spontaneous emission, the decay of the cavity mode and deviation of the coupling strength. The experimental feasibility of our proposal is also discussed.     

Remote Information Concentration via a Four-Particle Cluster State

We propose a protocol of remote information concentration achieved by a four-particle cluster state. To achieve the task, Bell state measurement and unitary operation are needed. The result shows a peculiar phenomenon that the remote information concentration is not always successful but with certain probability.     

两个力学量算符具有共同本征态系的条件

量子力学是人们了解微观世界的一门重要的课程.在量子力学中,由于任何实物体都具有波粒二象性,必须用算符来表示力学量,因此算符理论显得尤为重要.在研究多个算符时,有一个非常重要的定理:两个力学量算符能够具有共同本征函数系的充分必要条件是这两个个力学量算符能够互相对易.本文分析了在使用该定理时可能存在的一些问题,并对这些问题进行了澄清.     

Genuine （k,m）-Threshold Controlled Teleportation and Multipartite Entanglement

We propose genuine (k,m)-threshold controlling schemes for controlled teleportation via multi-particle entangled states, where the teleportation of a quantum state from a sender (Alice) to a receiver (Bob) is under the control of m supervisors such that k (k ≤ m) or more of these supervisors can help Bob recover the transferred state. By construction, anyone of our quantum channels is a genuine multipartite entangled state of which any two parts areinseparable. Their properties are compared and contrasted with those of the well-known GHZ, W, and linear cluster states, and also several other genuine multipartite entangled states recently introduced in the literature.     

辐射场中二能级原子的量子态保真度

利用半经典理论和量子理论研究辐射场与二能级原子(量子位)的相互作用,给出二能级原子的量子态保真度表达式.讨论了不同的原子初始态条件下,半经典理论中辐射场强度对量子态保真度的影响和量子理论中辐射场光子数对量子态保真度的影响.结果表明:在半经典理沦中,当原子与辐射场发生共振相互作用时,初始处于叠加态的原子的量子态保真度与辐射场强度无关;原子的量子态保真度随时间呈周期性演化,其演化的频率受辐射强度或光子数调制.此外,选择适当的失谐量,能够有效地改变量子信息的保真度.     

量子纯态与混合态中力学量测量研究

量子纯态和混合态是量子信息中最重要的两种量子态,是研究密度算符、量子纠缠态和量子消相干的基础.量子纯态与混合态具有本质区别.量子干涉的一个最重要的特征是量子纯态的相对位相有可以观测的效应.利用量子力学的方法,通过测定特定力学量(σ)z,(σ)x和(σ)n的取值来分析从纯态到混合态的转变.结果表明:量子纯态中的测量是各向异性的,而对于混合态则是各向同性的.     

量子逻辑门的算符及矩阵表示

将量子逻辑门视为量子力学体第,利用泡利算符,系统研究了量子逻辑门的哈密顿算符及幺正变换的矩阵表示,论述了把量子逻辑门的输入输出态与量子 体系波函数一起来的方法,结果有利于指导在实际中选取合适的遵守量子力学定律的两态系统完成量子逻辑操作。     

量子位叠加态的防错纠错编码

提出用单个量子位的叠加态进行量子编码,采用分组纠错方法,设置纠错量子线路;用８个量子们编码时,建立同态量子位对模型,简化了量子编码。     

非旋波近似中两能级原子与热库相互作用时原子的消相干特性

两能级原子与外部环境（热库）相互作用时,采用非旋波近似,研究原子与热辐射场单光子和双光子作用过程,利用小系统与库耦合行为的量子理论,计算原子约化密度矩阵非对角元,分析原子状态的消相干特性。     

消除高强度光腔三光子过程中两能级原子的消相干性

研究置于外部环境(热库)中的两能级原子在外加驱动场时原子的消相干问题.得到高强度光腔三光子过程中原子约化密度算符非对角元.在两能级原子的消相干被消除的情况下,讨论外加驱动场的特性.