Variations of water’s local-structure induced by solvation of NaCl

The researches on the structure of water and its changes induced by solutes are of enduring interests. The changes of the local structure of liquid water induced by NaCl solute under ambient conditions are studied and presented quantitatively with some order parameters and visualized with 2-body and 3-body correlation functions. The results show that, after the NaCl are solvated, the translational order t of water is decreased for the suppression of the second hydration shells around H₂O molecules; the tetrahedral order ｜q｜ of water is also decreased and its favorite distribution peak moves from 0.76 to 0.5. In addition, the orientational freedom k and the diffusion coefficient D of water molecules are reduced because of new formed hydrogen-bonding structures between water and solvated ions.     

High-capacity three-party quantum secret sharing with superdense coding

This paper presents a scheme for high-capacity three-party quantum secret sharing with quantum superdense coding, following some ideas in the work by Liu et al (2002 Phys. Rev. A 65 022304) and the quantum secret sharing scheme by Deng et al (2008 Phys. Lett. A 372 1957). Instead of using two sets of nonorthogonal states, the boss Alice needs only to prepare a sequence of Einstein--Podolsky--Rosen pairs in d-dimension. The two agents Bob and Charlie encode their information with dense coding unitary operations, and security is checked by inserting decoy photons. The scheme has a high capacity and intrinsic efficiency as each pair can carry 2lbd bits of information, and almost all the pairs can be used for carrying useful information.     

尿嘧啶、水合尿嘧啶的结构和振动性质研究

基于从头计算方法和半经验势分子动力学,通过计算尿嘧啶分子及其水合尿嘧啶分子运动轨迹的速度自关联函数的傅立叶变换,给出了这些分子的振动频率。通过求解Hessian矩阵,鉴别出这些分子每一个振动频率的振动模式。对孤立的尿嘧啶分子,计算结果能够和实验数据符合。对水合尿嘧啶分子中,尿嘧啶分子的结构和振动频率的改变做了讨论。Based on an ab initio calculation and a semiempirical method, the structural and vibrational frequencies of Uracil and hydrated Uracil are studied by using the Fourier transform of velocity autocorrelation function of trajectories of molecular dynamics simulations. The finite difference harmonic method is also used to assign the vibrational frequency of each mode. It is found the calculation frequencies are in good agreement with the experiment data. The structural and vibrational frequencies of Uracil in hydrated form is discussed.     

Efficient Polarization Entanglement Purification Using Spatial Entanglement

The protocol using spatial entanglement to purify polarization entanglement by entanglement transformation between different degrees of freedom in a realistic environment is elaborated. Our analyses show that the bit-flip error can be completely purified, but the pure maximally entangled state can not be obtained ultimately if the spatial entanglement is impure. The fidelity of the purified state is decided by the spatial entanglement. Furthermore, this protocol can also be extended to purify the multi-particle Greenberg—Horne—Zeilinger （GHZ） state. It is presented that the spatial entanglement can be served as another source to improve the quality of entanglement.     

低能质子环束流与等离子体相互作用过程的一维混合模拟研究

运用一维混合模拟方法, 研究了垂直于等离子体磁场入射的低能质子环束流与等离子体的相互作用过程. 结果显示: 由质子环束流激发的等离子体波首先经历指数式快速增长的线性阶段, 随后出现饱和、衰减和相对稳定的非线性阶段. 在线性阶段, 质子束投掷角散射使波模共振作用迅速减弱, 波的增长很快出现饱和. 随后, 持续的投掷角散射, 使入射质子在速度空间从环状分布渐变为均匀分布, 同时初始阶段的右手共振不稳定性逐渐消失, 在最后相对稳定阶段只存在阿尔芬波. 研究发现, 背景等离子体的有效加热始于非线性阶段, 等离子体波的形成有助于将质子束动能转换为背景等离子体的热能.     

应变石墨烯纳米带谐振特性的分子动力学研究

从动势能转换与守恒原理出发,在微正则(NVE)系综下,采用COMPASS力场对石墨烯纳米带及其应变传感器的谐振特性进行了分子动力学模拟.研究发现,非线性响应主导了石墨烯纳米带的动态行为,而其超高的基波频率则与长度和边界条件密切相关;单轴拉伸应变对石墨烯纳米带基波频率的影响显著且强烈依赖于边界条件,四边固支型应变石墨烯纳米带具有更高的频移,其灵敏度可高达7800 Hz/nanostrain,远大于相同长度碳纳米管应变传感器的灵敏度;石墨烯纳米带及其应变传感器的谐振特性均与手性无关.本文所得结果表明,由于超低 关键词： 石墨烯纳米带 分子动力学 应变 基波频率     

A two-step quantum secure direct communication protocol with hyperentanglement

We propose a two-step quantum secure direct communication (QSDC) protocol with hyperentanglement in both the spatial-mode and the polarization degrees of freedom of photon pairs which can in principle be produced with a beta barium borate crystal. The secret message can be encoded on the photon pairs with unitary operations in these two degrees of freedom independently. This QSDC protocol has a higher capacity than the original two-step QSDC protocol as each photon pair can carry 4 bits of information. Compared with the QSDC protocol based on hyperdense coding, this QSDC protocol has the immunity to Trojan horse attack strategies with the process for determining the number of the photons in each quantum signal as it is a one-way quantum communication protocol.     

CdSe的电子结构和光学性质研究

CdSe是Ⅱ-Ⅵ族半导体材料中一种重要的半导体材料,它有闪锌矿和纤锌矿两种不同的结构,带隙较窄,具有优良的电光特性和广泛的应用前景,得到了人们的广泛关注[1-3].     

超强飞秒激光脉冲作用下氢分子的高次谐波行为——基于含时密度泛函理论的模拟

在含时密度泛函理论框架下,采用经典和量子相结合的模型,模拟了氢分子在超强飞秒激光脉冲作用下的高次谐波行为. 结果表明氢分子的高次谐波谱具有“下降—平台—截止”的结构和偶次谐波被禁闭仅出现奇次谐波的选择性特征;不同的激光偏振方向会导致高次谐波的截止频率和谱线强度的变化. 关键词： TDDFT 超强飞秒激光 高次谐波 2分子')" href="#">H₂分子     

Mo硫化物/Ti复合薄膜的制备及其环境摩擦磨损性能研究

采用高温硫化处理磁控溅射Mo/Ti金属前驱体薄膜制备Mo硫化物/Ti复合薄膜,采用X射线衍射仪、能谱仪和扫描电子显微镜对复合薄膜的组织结构、化学成分和表面形貌进行分析,采用涂层附着力自动划痕仪和可控气氛球-盘式摩擦磨损试验仪分别测试薄膜与基体的结合力以及摩擦系数,并用扫描电子显微镜观察薄膜的磨损表面形貌,分析其磨损机制.结果表明:硫化温度在450 ℃以上时能够生成较多Mo硫化物,最佳硫化工艺为450 ℃×15 h;提高硫化温度或延长硫化时间均使薄膜的结合力下降;磁控溅射Mo/Ti前驱体复合薄膜经450 ℃×15 h硫化处理后,薄膜中生成复杂的Mo硫化物,形成Mo硫化物/Ti复合薄膜;与纯Mo薄膜硫化后相比,Mo硫化物/Ti复合薄膜具有更高的界面结合力和更优异的摩擦磨损性能.