Cloaking an object in a half space without reflection

A novel cloaking scheme to hide an object in a half space from electromagnetic (EM) detection without reflection is firstly presented. The proposed cloaking scheme contains a couple of matching strips, which consist of an isotropic material layer and an anisotropic UPML layer, located right under the bottom surface of a semi-cylindrical cloaking shell. Simple expressions for the material parameters of the cloaking scheme are derived. Numerical simulations are also performed, and a good cloaking effect is achieved. The cloaking scheme is effective to hide the local object with strong scattering characters placed on mobile carriers, such as the radar antenna system on an aircraft.1     

Deterministic assisted clone of an unknown four-particle entangled cluster-type state

Two deterministic schemes are proposed to realize the assisted clone of an unknown four-particle entangled cluster- type state. The schemes include two stages. The first stage requires teleportation via maximal entanglement as the quantum channel. In the second stages of the protocols, two novel sets of mutually orthogonal basis vectors are constructed, With the assistance of the preparer through a four-particle or two-step two-particle projective measurement under these bases, the perfect copy of an original state can be produced. Comparing with the previous protocols which produce the unknown state and its orthogonal complement state at the site of the sender, the proposed schemes generate the unknown state deterministically.     

基于原子系综四波混频过程的量子信息协议

与经典体系相比,量子信息协议在大幅提高信息处理的安全性、保真度和容量方面具有巨大的优势。各种具有不同功能的量子信息协议已经被提出并实现。介绍了利用铷原子四波混频过程构建一套能兼容多种不同量子信息协议的多功能平台。基于这个平台可以实现并行9通道全光量子隐形传态,部分无实体量子态传输和最优N→M相干态量子克隆协议。更重要的是,部分无实体量子态传输协议可以同时连接全光量子隐形传态协议和最优1→M相干态量子克隆协议。这些量子信息协议在全光量子通信中具有潜在的应用。     

利用热平衡态超导电荷量子比特实现量子隐形传态

本文利用处于热平衡态的两个相同超导电荷量子比特纠缠态作为量子隐形传态的信道,给出标准量子隐形传态协议下传递单量子比特态和两量子比特态的纠缠以及非标准协议下传递单量子比特态时平均保真度的解析表达式,研究其随温度、约瑟夫森能等系统参数的变化情况．计算结果表明,在标准量子隐形传态协议下传递两量子比特之间的纠缠以及非标准量子隐形传态协议下传递单量子比特态时可以实现接近理想的量子隐形传态．     

卷云对自由空间星地量子通信信道的影响

卷云对量子通信光信号的传输有极大的影响.根据卷云特性建立了卷云冰晶粒子的分布模型,研究了卷云的消光特性,并根据卷云的散射特性,分析了卷云冰水含量、传输距离、链路消光特性、信道容量和信道纠缠度衰减的定量关系,研究了噪声影响下隐形传态保真度的变化,并进行了仿真实验.实验结果表明,当传输距离为3 km时,在卷云冰水含量(体积质量)为0.4g·m-3的条件下,对应的链路衰减、信道容量和信道纠缠度分别为0.05 dB· km-1、0.94 dB· km-1和0.52,而在卷云冰水含量(体积质量)为0.1g·m-3的条件下,对应的链路衰减、信道容量和信道纠缠度分别为0.20 dB·km-1、0.82 dB· km-1和0.07.由实验结果可见,自南空间量子通信信道的性能在卷云的影响下均发生了不同程度的变化.因此,在进行量子通信时,需考虑卷云的影响,根据卷云的变化调整性能参数,以提高通信质量.     

A Note on Teleportation of an Arbitrary Two-Particle State Without Bell-State Measurement in Cavity QED

We present a scheme using four two-level atoms and a bimodal cavity to get approximate conditional teleportation of an arbitrary entangled atomic state without using the Bell-state measurement.     

Teleportation of a Bipartite Entangled Coherent State via a Four-Partite Cluster-Type Entangled State

We present an optical scheme to almost completely teleport a bipartite entangled coherent state using a four-partite cluster-type entangled coherent state as quantum channel. The scheme is based on optical elements such as beam splitters, phase shifters, and photon detectors. We also obtain the average fidelity of the teleportation process. It is shown that the average fidelity is quite close to unity if the mean photon number of the coherent state is not too small.     

Threshold Multiparty Controlled Teleportation of Arbitrary m-Qubit Quantum Information

We present a （t, .n） threshold multiparty controlled quantum teleportation protocol of an arbitrary m-qubit quantum state between two remote parties. The unknown m-qubit quantum state can be recovered by the receiver under control of a subset of the n controllers if the number of the subset is larger than or equal to a threshold, say, t, but not for any t - 1 or fewer controllers. Our scheme seems to be more practical and more flexible than other existing protocols. The quantum resource required is just m Einstein-Podolsky-Rosen （EPR） pairs plus some single photons. The techniques required are only Bell state measurement, single-qubit unitary operation and yon Neumann measurement. So our scheme is also feasible with present-day technique.     

Continuous-Variable Quantum Teleportation of Entangled Coherent States

We propose a quantum teleportation scheme for tripartite entangled coherent state （ECS） with continuous variable. Our scheme is feasible and economical in the sense that we need only linear optical devices such as beam splitters, phase shifters and photon detectors and employ three bipartite maximally ECSs as quantum channels. We also generalize the tripartite scheme into multipartite ease and calculate the minimum average fidelity for the schemes in tripartite and multipartite cases.     

利用cluster态隐形传送任意三原子W态

提出一个隐形传送任意三原子纠缠W态的方案,在此方案中,选用由四个全同的二能级原子组成的cluster态作为量子信道.研究表明,接收者基于发送者的经典信息,借助于一个附加原子,实行联合幺正变换以及单原子幺正变换,可实现三原子W态的隐形传送.该方案不受外界热场和腔场耗散的影响,不需要贝尔态测量,成功实现传送的几率为1.