Probabilistic remote preparation of a two-atom entangled state

A scheme for remotely preparing a two-atom entangled state via entanglement swapping in cavity quantum electronic dynamics （QED） with the help of separate measurements is proposed. And the effect of cavity decay is eliminated in our scheme.     

Three-Party Quantum State Sharing of an Arbitrary Unknown Two-Qubit State Based on Entanglement Swapping and Bell-State Measurements

We propose a scheme for sharing an arbitrary unknown two-qubit state among three parties by using a four-qubit cluster-class state and a Bell state as a quantum channel. With a quantum controlled phase gate （QCPG） operation and a local unitary operation, any one of the two agents has the access to reconstruct the original state if he/she collaborates with the other one, whilst individual agent obtains no information. As all quantum resource can be used to carry the useful information, the intrinsic efficiency of qubits approaches the maximal value. Moreover, the present scheme is more feasible with present-day technique.     

用电吸收调制器实现标记擦除的新方法

提出一种结构简单、易于实现的正交光标记擦除的新方法.利用频移键控调制产生80 Gbit/s载荷,采用强度调制产生2.5 Gbit/s标记,然后利用电吸收调制器在分组交换网络核心节点处擦除旧标记,再加入新标记实现信息在网络中继续传输.理论分析和数值模拟验证了此方案擦除标记的可行性.     

Arbitrary Lagrangian Eulerian formulation for two-dimensional flows using dynamic meshes with edge swapping

The dynamic modification of the computational grid due to element displacement, deformation and edge swapping is described here in terms of suitably-defined continuous (in time) alterations of the geometry of the elements of the dual mesh. This new interpretation allows one to describe all mesh modifications within the arbitrary Lagrangian Eulerian framework, thus removing the need to interpolate the solution across computational meshes with different connectivity. The resulting scheme is by construction conservative and it is applied here to the solution of the Euler equations for compressible flows in two spatial dimensions. Preliminary two dimensional numerical simulations are presented to demonstrate the soundness of the approach. Numerical experiments show that this method allows for large time steps without causing element invalidation or tangling and at the same time guarantees high quality of the mesh elements without resorting to global re-meshing techniques, resulting in a very efficient solver for the analysis of e.g. fluid-structure interaction problems, even for those cases that require large mesh deformations or changes in the domain topology.     

Quantum steganography with a large payload based on dense coding and entanglement swapping of Greenberger-Horne-Zeilinger states

A quantum steganography protocol with a large payload is proposed based on the dense coding and the entanglement swapping of the Greenberger-Horne-Zeilinger (GHZ) states. Its super quantum channel is formed by building up a hidden channel within the original quantum secure direct communication (QSDC) scheme. Based on the original QSDC, secret messages are transmitted by integrating the dense coding and the entanglement swapping of the GHZ states. The capacity of the super quantum channel achieves six bits per round covert communication, much higher than the previous quantum steganography protocols. Its imperceptibility is good, since the information and the secret messages can be regarded to be random or pseudo-random. Moreover, its security is proved to be reliable.     

连续变量无条件纠缠交换 --纠缠态的量子离物传送

利用自行设计的两台非简并光学参量放大器，获得了一对具有经典相干性且量子起伏相互独立的连续变量纠缠态光场，并用它完成了连续变量的无条件纠缠交换，即纠缠态的量子离物传送．通过联合贝尔态探测与纠缠塌缩，使两个初始不纠缠而又从未发生过直接相互作用的光场产生了量子纠缠，其正交振幅和位相分量的量子起伏关联方差被直接测量，其测量值分别低于散离噪声极限1．23dB和1．12dB．理论计算与实验结果基本符合．     

基于腔QED的无信息泄露量子对话(英文)

良好的安全性对量子保密通信协议而言是不可或缺的,但信息泄露已成为量子对话的一个严重安全威胁.为了解决信息泄露问题,利用腔QED中原子的演化规律提出一个基于腔QED的无信息泄露量子对话协议,利用腔QED中两个Bell态纠缠交换后的测量相关性来克服信息泄露问题.研究表明:该协议能够通过安全检测探测到外部窃听者的主动攻击,如截获-重发攻击、测量-重发攻击和纠缠-测量攻击;在每轮通信可以安全交换4比特秘密信息;对信息泄露问题和外部窃听者的主动攻击,都具备良好的安全性.     

Entanglement swapping of continuous variable using squeezed vacuum states

We present a realistic scheme for the entanglement swapping of continuous variable, in which a two-mode squeezed vacuum state serves as a quantum channel. The position sum and momentum difference of two local modes are measured. By taking the input entangled state also as a two-mode squeezed vacuum state, we investigate the average fidelity and the von Neumann entropy of the output state. The results show that the perfect teleportation can be achieved by increasing the squeezing of the quantum channel and that any nonzero squeezing in both the quantum channel and the input entangled state is sufficient to swap the entanglement.