实现光子的远程量子操作

量子纠缠的非局域性质为量子信息应用提供了强有力的工具,利用量子纠缠态可以实现量子隐形传态、量子密集编码、量子密码、远程量子态制备、远程量子态测量.这里,我们将给出一个基于两粒子纠缠态的利用局域操作和经典通信的远程量子操作的实验方案.该方案可以实现对单光子偏振态在Bloch球空间中绕固定方向进行任意旋转操作,或者绕任意方向进行180度旋转操作.     

Bose-Hubbard模型中系统初态对量子关联的影响

量子关联是量子信息、量子计算与量子计量领域的重要资源, 在量子纠缠和贝尔非局域性中, 两子系统起着同等关键的作用, Einstein-Podolsky-Rosen (EPR)量子引导关联的强度介于量子纠缠和贝尔非局域性之间, 对单向EPR量子引导关联而言两子系统的作用不对等. 本文研究了双模Bose-Hubbard模型中模间量子关联的动态特性, 揭示了EPR量子引导关联的取向对系统初态模间交换对称性的依赖关系. 根据Hillery-Zubairy纠缠判据以及基于最大平均量子Fisher信息的纠缠判据考察了系统初态对模间量子纠缠演化规律的影响. 如果模间耦合强度远大于同一势阱内粒子间的相互作用, 初始处于SU(2)相干态的系统在具有确定的两子系统交换对称性的条件下, 其量子关联呈现简单的周期性演化规律; 当这种对称性破缺时, 模间量子关联的演化呈现较复杂的崩塌与回复现象.     

利用Cluster State实现远程态制备

量子态是量子信息的载体，因此，从某种意义上说，量子信息过程就是量子态的传递和操作的过程。量子态的远程制备包括量子隐形传态（Telepotation）和远程态制备（Remote State Preparation（RSP））。远程态制备是一种利用纠缠和经典通讯传输量子态的简单方法，相比较量子态telepotation耗费的资源更少（1 ebit and 1 cbit）。Cluster State是一种特殊的量子态，在量子计算方案中有着广泛的应用。我们实验上利用SPDC产生的偏振纠缠双光子，加入时间比特，构造出Cluster State，并利用Cluster State实现了量子态的远程制备。     

利用两对二粒子非最大纠缠态概率隐形传送任意三粒子纠缠W态

提出一种仅利用两对二粒子非最大纠缠态作为量子信道传送任意三粒子纠缠W态的方案,与以往的方法相比,本方案不仅节约了纠缠资源(以往的量子信道三对EPR或者三粒子纠缠态),而且由于作为量子信道的二粒子纠缠态要比任何别的三粒子纠缠态在实验上更容易制备,因而本方案在量子信息理论与实验的发展中都具有参考价值.     

2（×）n量子系统二参量一类态的量子相对熵纠缠度

对于任意的两体量子系统，总可以通过局域操作和经典通讯变换成二参量的一类态。本文计算了2（×）n量子系统的两参量一类态的量子相对熵纠缠度，找到了与其最接近的可分离态，得出了具体的解析表达式，并与其他纠缠的度量一负值度和形成纠缠度作了比较，三种纠缠的度量从大到小的依次为负值度、形成纠缠度和量子相对熵纠缠度。     

利用二粒子部分纠缠态实现开靶目标的非局域量子可控非（CNOT）门的受控操作

提出利用二粒子部分纠缠态概率性地实现开靶目标的非局域量子可控非（CNOT）门的操控方案.首先考虑利用3个二粒子部分纠缠态实现3个靶目标共享的非局域量子CNOT门的受控操作,然后将该方案推广到N个靶目标共享的情形. 在该方案中,控制端Alice的局域正定算符值测量（POVM）起着关键作用,给出了该测量算符的数学表式.值得注意的是, 用二粒子部分纠缠态可确定性地实现非局域CNOT门. 关键词： 二粒子部分纠缠态 非局域可控非门 开靶目标 正定算符值测量     

解说量子纠缠理论

量子纠缠态在量子信息处理,如量子隐形传态、量子密集码、量子纠错、量子保密通信、量子计算等过程中起了十分重要的作用.量子纠缠理论主要研究量子态的纠缠刻画、分类及其在量子信息处理中的应用.文章介绍了量子纠缠理论中的一些基本概念和结果,其中包括:量子力学的实在性、局域性的讨论与Bell不等式的联系,Bell不等式与量子态可分性间的关系;纯态和混合态可分性的定义及若干判别准则(包括矩阵正映照方法、部分转置判据、约化判据、重排判据、纠缠见证、协方差判据及局域测不准关系判据);部分纠缠度量的介绍(包括纠缠形成、并发度、相对熵、负度、缠结和纠缠帮助,以及纠缠度量的计算和上下界的估算).     

量子关联简介

量子纠缠作为一种非局域的关联,是一种重要的资源而被广泛应用于量子信息处理。然而,最近的研究结果发现,可分态中也可以存在非经典的关联,量子纠缠只是量子关联的一部分;非纠缠的量子关联在一些量子通信和量子计算任务中扮演着重要的角色。文章简要综述了量子关联的基本概念,描述了几种常见的量子关联度量,并介绍了量子关联在量子信息处理中的作用以及一些最新动态。     

三组份纠缠与可控连续变量量子密集编码

我们从量子理论出发,提出了利用分束器与非简并光学参量放大器产生三组份量子纠缠态光场[1,2]并用以执行可控连续变量量子密集编码的新方案.在三个组份非局域纠缠的基础上,发送站(Alice)与接收站(Bob)之间的通讯受控于另一指挥部(Claire).实验方案采用明亮的GHZ三组份纠缠光束为信息载体,使用Bell态直接探测方式提取信息,不需要本底振荡光,从而简化了实验系统.所设计的系统可用于量子保密通讯和量子网络.     

退相干条件下两比特纠缠态的量子非局域关联检验

量子纠缠态的量子非局域关联特性在当前量子信息和量子计算协议中起着重要的作用.然而,任何实际的物理系统都不可避免地与周围环境相互作用,使得在量子信道中的传输过程中,量子态会发生相干性退化,进而弱化量子态的量子非局域关联特性.本文利用一种基于Hardy-type佯谬的高概率量子非局域关联检验方案,分别研究了两比特偏振纠缠态在经过振幅阻尼信道(ADC)、相位阻尼信道(PDC)和退极化阻尼信道(DC)后的量子非局域关联检验情况.研究结果表明,DC传输信道对量子态的量子非局域关联检验特性影响较大,而PDC传输信道对量子态的量子非局域关联检验特性影响较小.最后,本文还给出了利用弱测量结合弱测量反转操作克服ADC退相干时,偏振纠缠态成功进行量子非局域关联检验的条件.结果表明,当弱测量的强度增大时,可有效地降低ADC退相干效应对偏振纠缠态成功进行量子非局域关联检验造成的影响.     

Nuclear interactions of 200 GeV protons in emulsion

Proton-nucleus interactions have been studied in nuclear emulsion exposed to the NAL 200 GeV proton beam. The inelastic mean free path is found to be 35.5 ± 0.8 cm and the average shower particle multiplicity is 12.9 ± 0.2. The angular distribution reveals some characteristics features of proton-nucleus interactions.     

Intensities and strong interaction attenuation of kaonic X-rays

Relative intensities of numerous kaonic X-ray transitions have been measured for the elements C,P,S, and C1, from which level widths due to the strong K-nucleus absorption have been determined. From these and earlier published data, optical potential parameters have been derived and possible consequences on the nuclear matter distribution are discussed.     

A study of the reactions π−p → K1X, K1Σ and K1Y11(1385) at 3.93 GeV/c

We have investigated the final states K¹⁰(890)Σ, $\text{K}{}^{10}\text{(890)Σ}{}^0$ and K¹⁰(890) Y₁¹⁰(1385) produced in π^?p interactions at 3.93 GeV/c. We present the differential cross sections and spin density matrix elements for the resonances as functions of momentum transfer, as well as the gL and Σ⁰ polarizations. The Σ⁰ polarization is found to be positive and maximal. An amplitude analysis is performed for the K¹ Λ and $\text{K}{}^1\text{Σ}{}^0$ reactions, and it is found that one natural parity transversity amplitude is dominant for the latter.     

Finite-energy corrections and multiplicity fluctuations according to the Gottfried model of hadron-nucleus interactions

Finite-energy corrections and multiplicity fluctuations are considered in the Gottfried model for hadron-nucleus high-energy interactions. The results are that there are appreciable corrections at Serpukhov-NAL energies, such that the Gottfried parameter is ν = 0.25–0.27 instead of, e.g., ν = 0.38, in better agreement with presently available experimental results for proton-nucleus collisions. Further, the sensitivity of the model to some of the input parameters results in appreciable fluctuations in multiplicity, the multiplicity distribution of the part stemming from repeated collisions inside the nucleus being at least as broad as a Poisson distribution.     

A study of the reactions KN→Σ(1385)π between 0.6 and 1.2 GeV/c

An energy-dependent partial-wave analysis of the reaction $\text{K}\text{N}\text{→Σ(1385)π}$ has been performed in the energy region lying between 1.65 and 1.85 GeV. The resonant amplitudes of seven well known Y¹ resonances have been determined, and used to compute the corresponding (8) ? (10) SU (3) coupling constants.     

Path integrals and the indefiniteness of the gravitational action

The Euclidean action for gravity is not positive definite unlike those of scalar and Yang-Mills fields. Indefiniteness arises because conformal transformations can make the action arbitrarily negative. In order to make the path integral converge one has to take the contour of integration for the conformal factor to be parallel to the imaginary axis. The path integral will then converge at least in the one-loop approximation if a certain positive action conjecture holds. We perform a zeta function regularization of the one-loop term for gravity and obtain a non-trivial scaling behaviour in cases in which the background metric has non-zero curvature tensor, and hence non-trivial topologies.     

Experimental tests of the factorisation of Regge trajectories in the proton fragmentation region

We present double differential cross sections for the reactions K^? + p → π^± + anything at 8.25 GeV/c. Using published data for reactions K⁺ + p→ π^? + anything and p + p → π⁺ anything we predict the differential cross sections for γ + p → π^? + anything, π^? + p → π^? + anything and π^? + p → π⁺ + anything in the target fragmentation region based on factorisation of the pomeron and Regge trajectories. Our predictions agree with the experimental data and support the hypothesis of factorisation of the Regge trajectories in the target fragmentation region.     

空芯光纤中介质层材料色散的研究

提出一种根据实验测量的损耗谱曲线,通过曲线拟合等方法获得空芯光纤巾介质层薄膜材料色散性质的方法,并使用此方法得到了数种空芯光纤中常用的介质层材料在可见光与近红外Ⅸ域的色散柯西公式.将得列的介质层材料色散引入到空芯光纤传输损耗谱的理论计算中之后,相对于小考虑材料色散或者使用文献中提供的色散数据进行计算的结果,理论计算结果能更好地符合实验测量结果,从而能够在理论上更加准确地预估空芯光纤在可见光与近红外区域的低损耗窗口的位置.所获得的材料色散柯西公式对于空芯光纤的高性能化没计有重要的辅助作用.     

On the slope of the scalar Kℓ3 decay form factor

We discuss a mechanism, based on exact threshold theorems in the limit of SU(2) × SU(2) symmetry, which can be used to estimate a certain suppression of the scalar K_?3 decay form factor at low momentum transfers, while maintaining the validity of the Callan-Treiman relation.     

Structures symplectiques, structures complexes, spineurs symplectiques et transformation de Fourier

Planck's constant is very useful in the development of the theory of symplectic Clifford algebras introduced by the author in 1977 [1,a], and to solve many connected problems for example the Poisson Lie algebra deformations [1,c]. In this paper we give a precise link between a complex structure J and the Fourier transform which is nothing but the natural left action of the covering J? of J in a symplectic convenient spinor space (modulo a constant factor).Thus Fourier transform becomes a geometric transformation separated from integration technics, good peculiarity for global problems. We explain nice algebraic properties of the Fourier transform taking them in the symplectic context with adapted metric in any signature. Some applications are given: Hermite's functions, Plancherel-Parseval's theorem, covariance problemes … . Our approach is particularly convenient for explain results in Maslov's theory [1,b] and the difficulties in defining a global Fourier transform over a symplectic manifold.