Capacity of a Simultaneous Quantum Secure Direct Communication Scheme between the Central Party and Other M Parties

We analyse the capacity of a simultaneous quantum secure direct communication scheme between the central party and other M parties via M＋1-particle GHZ states and swapping quantum entanglement. It is shown that the encoding scheme should be secret if other M parties wants to transmit M ＋ 1 bit classical messages to the centre party secretly. However, when the encoding scheme is announced publicly, we prove that the capacity of the scheme in transmitting the secret messages is 2 bits, no matter how large M is.     

Perfect quantum teleportation and dense coding protocols via the 2N-qubit W state

In this paper, we investigate perfect quantum teleportation and dense coding by using an 2N-qubit W state channel. In the quantum teleportation scheme, an unknown N-qubit entangled state can be perfectly teleported. One ebit of entanglement and two bits of classical communication are consumed in the teleportation process, just like when using the Bell state channel. While N+1 bits of classical information can be transmitted by only sending N particles in the dense coding protocol.     

Detecting high-dimensional multipartite entanglement via some classes of measurements

Mutually unbiased bases, mutually unbiased measurements and general symmetric informationally complete measurements are three related concepts in quantum information theory. We investigate multipartite systems using these notions and present some criteria detecting entanglement of arbitrary high dimensional multi-qudit systems and multipartite systems of subsystems with different dimensions. It is proved that these criteria can detect the k-nonseparability(k is even) of multipartite qudit systems and arbitrary high dimensional multipartite systems of m subsystems with different dimensions.We show that they are more efficient and wider of application range than the previous ones. They provide experimental implementation in detecting entanglement without full quantum state tomography.     

六光子超纠缠态制备方案

自发参量下转换对应于一种非线性光学过程, 实验上作为一种标准方法, 人们利用自发参量下转换源产生纠缠光子对. 本文考虑由自发参量下转换源产生三对纠缠光子的情况. 通过使用由几组偏振光 束分束器、分束器和半波片等线性光学器件组成的量子线路演化三对光子, 给出了一个高效制备 包含偏振纠缠和空间纠缠的六光子超纠缠态方案. 因为方案中包含了参量下转换源产生三对纠缠光子 的所有可能情况, 所以本方案有很高的效率. 基于弱非线性介质构建了一个量子非破坏性测量装置, 用于区分光子在两指定的空间模中的两种分布情况. 特别地, 方案中可以通过合理约束在量子非破坏性测量过程中引入的非线性强度来达到实际实验所限定的数量级, 因此, 该方案易于在实验上实现.     

Probabilistic Dense Coding Using Non-Maximally Entangled Three-Particle States

We present a scheme for probabilistic dense coding via quantum channels of non-maximally entangled threeparticle states. Quantum dense coding will succeed with a certain probability if the sender introduces an auxiliary particle and performs a collective unitary transformation. The average information transmitted in this scheme is calculated.     

Probabilistic Chain Teleportation of a Qutrit-State

We investigate chain teleportation of a qutrit-state via the non-maximally two-qutrit entangled channels. For the case of four parties, the efficiencies of two chain teleportation protocols, the separate chain teleportation protocol （SCTP）, and the global chain teleportation protocol （GCTP）, are calculated. In SCTP the errors are corrected between every step while in GCTP the errors are corrected only at the end. Furthermore, we present a piecewise global chain teleportation protocol （PGCTP） for keeping away from the inconvenience of error-correction of GCTP. We show that PGCTP is more efficient than SCTP.     

Two-Step Deterministic Remote Preparation of an Arbitrary Quantum State

We present a two-step deterministic remote state preparation protocol for an arbitrary qubit with the aid of a three-particle Greenberger-Horne-Zeilinger state. Generalization of this protocol for higher-dimensional Hilbert space systems among three parties is also given. We show that only single-particle yon Neumann measurements, local operations, and classical communication are necessary. Moreover, since the overall information of the quantum state can be divided into two different pieces, which may be at different locations, this protocol may be useful in the quantum information field.     

Probabilistic Teleportation of Two-Particle State of General Formation in Ion Trap

We propose a scheme for the probabilistic teleportation of an unknown two-particle state of general formation in ion trap. It is shown that one can realize experimentally this teleportation protocol of two-particle state with presently available techniques.     

Entanglement evolution of three-qubit mixed states in multipartite cavity—reservoir systems

We analyze the multipartite entanglement evolution of three-qubit mixed states composed of a GHZ state and a W state.For a composite system consisting of three cavities interacting with independent reservoirs,it is shown that the entanglement evolution is restricted by a set of monogamy relations.Furthermore,as quantified by the negativity,the entanglement dynamical property of the mixed entangled state of cavity photons is investigated.It is found that the three cavity photons can exhibit the phenomenon of entanglement sudden death(ESD).However,compared with the evolution of a generalized three-qubit GHZ state which has the equal initial entanglement,the ESD time of mixed states is later than that of the pure state.Finally,we discuss the entanglement distribution in the multipartite system,and point out the intrinsic relation between the ESD of cavity photons and the entanglement sudden birth of reservoirs.     

格序环的一个根的结构

从不同角度刻画了格序环Ｒ的Ｐ－根和ｌ－Ｂ根，并对ｌ－Ｑ根环进行了讨论．揭示了Ｒ及Ｒ上的全矩阵环Ｒｎ的ｌ－Ｑ根，ｌ－Ｑ理想，素ｌ－理想，半素ｌ－理想之间的关系．