排序方式: 共有13条查询结果,搜索用时 15 毫秒
1.
Utilizing a proper positive operator-valued measure (POVM) instead of usual projective measurement, we present a new scheme
for remote preparation of a general two-qubit state in either distant ministrant’s place. In the scheme, we exploit a GHZ-type
state and a W-type state as the shared quantum channel, and the remote two-qubit preparation can be realized in a probabilistic
manner via two ministrants’ collaboration. Furthermore, we also explore the scheme’s applications to some special ensembles
of states in detail. The success probabilities in different cases are calculated, respectively, which show that the remote
preparation can be achieved with higher probability provided that the prepared state belongs to the special ensembles. 相似文献
2.
Molecular dynamics computer simulation based on the Born-Mayer-Huggins potential function has been carried out to study the effects of duster size and temperature on the nucleation rate of sodium chloride dusters in the temperature range of 580 K to 630 K. Clusters with 256 and 500 NaCl molecules have been studied and the results have been compared with those obtained from 108 molecule dusters. The melting point (MP) of the clusters were observed to increase with the size of the clusters and can be well described by a linear equation MP =1107(37)-1229(23)N^-1/3(N is the number of molecules in the duster).The nucleation rate was found to decrease with increasing the duster size or temperature. Various nucleation theories have been used to interpret the nucleation rates obtained from this molecular dynamics simulation. It is possible to use a constant diffuse interface thickness to interpret the nucleation rate from the diffuse interface theory in the temperature range of this study. However, the interfacinl free energy estimated from classical nucleation theory and diffuse interface theory increases too fast with increasing the temperature while that from Gran-Gunton theory does not change with changing temperatures.The sizes of critical nuclei estimated from all the theories are smaller than those estimated from our simulations. 相似文献
3.
BES Collaboration< BR> BAI Jing-Zhi BAN Yong BIAN Jian-Guo CAI Xiao CHANG Jin-Fan CHEN Hai-Xuan CHEN He-Sheng CHEN Hong-Fang CHEN Jiang-Chuan CHEN Jin CHEN Jun CHEN Ma-Li CHEN Yuan-Bo CHI Shao-Peng CHU Yuan-Ping CUI Xiang-Zong DAI Hong-Liang DAI You-Shan DENG Zi-Yan DONG Liao-Yuan DU Shu-Xian DU Zhi-Z 《中国物理C(英文版)》2004,28(4):325-331
Evidence of ψ(3770) decays to a non-DD final state is observed. A total of 6.8±3.0 ψ(3770)→J/ψ→π+π— events are obtained from a data sample of 8.0±0.5 pb-1 taken at center-of-mass energies around 3.773GeV using the BES-Ⅱ detector at the BEPC. The branching fraction is determined to be BF(ψ(3770)→J/ψ→π+π—)=(0.59±0.26±0.16)%, corresponding to the partial width of Γ(ψ(3770)→J/ψπ+π—)=(139±61±41)keV. 相似文献
4.
In the framework of T2HDM, we calculated the new physics contributions involving neutral Higgs bosons to the branching ratios of ^-Bs,d^0→e^+e^-(e= e,μ) decays. Comparing the theoretical predictions with the experimental upper-limits, we found that (a) The data of Br(^-Bs,d^0→e^+e^-) give the upper bound on tanβ: tanβ≤22, while Br(^-Bs^0→e^+e^-) give tanβ≤12 for fixed δ = 0^0, mH+ = 350 CeV, mH^0 = 160 GeV, mh^0 = 115 GeV and mA^0 = 120 GeV; (b) A light neutral Higgs boson mass mho (mA^0) less than 50 GeV (120 GeV) is excluded by the data of branching ratios for ^-Bs,d^0→e^+e^-(e = μ) decays with tanβ= 10; (c) The bounds on mh^0 and tanβ, or mA^0 and tanβ are strongly correlated: a smaller (larger) tanβ means a lighter (heavier) neutral Higgs boson. 相似文献
5.
In the framework of T2HDM, we calculated the new physics contributions involving neutral Higgs bosons to the branching ratios of B_(s,d)~0→e~+e~-(e=e,μ) decays. Comparing the theoretical predictions with the experimental upper-limits, we found that (a) The data of Br(B_d~0→e~+e~-)give the upper bound on tanβ: tanβ≤ 22, while Br(B_s~0→e~+e~-)give tanβ≤12 for fixed δ = 0°, m_H+=350 GeV, m_Ho = 160 GeV, m_Ho= 115 GeV and m_Ao=120 GeV; (b) A light neutral Higgs boson mass m_Ho (m_Ao) less than 50 GeV (120 GeV) is excluded by the data of branching ratios for B_(s,d)~0→e~+e~-(e=μ) decays with tanβ=10; (c) The bounds on m_(h~0) and tanβ, or m_(A~0) and tanβ are strongly correlated: a smaller (larger) tanβ means a lighter (heavier) neutral Higgs boson. 相似文献
6.
2,2,3-三甲基丁烷(C7H16)晶体的成核动力学 总被引:1,自引:0,他引:1
High temperature solid phase I of 2,2,3-trimethylbutane(C7H16)(TMB) was investigated by X-ray powder diffraction. The electron diffraction technique for observing the kinetics of phase transitions in the condensed matter has been applied to study the freezing of TMB clusters with diameter of~13nm. Cluster beams were generated from the supersonically expanded TMB vapor with mole fraction of 0.01 in neon carrier gas. The freezing evolution was monitored by electron diffraction in interval of 7-9 μs. Clusters with an average size of ~5,500 molecules were observed to freeze into the solid phase I at a nucleation rate of 3.5 × 1028 m-3•s- 1 at the freezing temperature of clusters, ~170K. The estimated growth rate of postcritical nuclei indicates that the observed nucleation in the present experiment corresponds to mononuclear freezing of the clusters into single crystals of solid phase I. 相似文献
7.
Molecular dynamics (MD) computer simulations have been carried out to study the structures, properties and crystal nucleation of nanoparticles with 453 Cu atoms. Structure information was analyzed from the MD simulations, while properties of nanoparticles of Cu453, such as melting point, freezing temperature, heat capacity and mo- lar volumes, have been estimated. The face center cubic (FCC) phase and icosahedron (Ih) phase were observed during the quenching process, and nucleation rates of crystallization to FCC crystal of Cu453 at temperatures of 650, 700, 750, and 800 K were analyzed. Both classical nucleation theory (CNT) and diffuse interface theory (DIT) were used to interpret our observed nucleation rates. The free energy and diffuse interface thickness between the liquid and the FCC crystal phases were estimated by the CNT and DIT respectively, and the results show that the DIT does not work properly to the system. 相似文献
8.
9.
Superconducting properties of barium in three phases under high pressure from first principles
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Electron-phonon coupling (EPC) in the three high-pressure phases of Ba is investigated using a pseudopotential plane-wave method based on density functional perturbation theory. The calculated values of superconducting critical temperature T c of Ba-I and Ba-II under pressure are consistent well with the trends observed experimentally. Moreover, Ba-V is found to be superconducting with a maximum T c exceeding 7.8 K at 45 GPa. With the increase of pressure, the values of T c increase in Ba I and Ba-II but the value of T c decreases in Ba-V. For Ba-I at pressures below 2 GPa, the increases of logarithmic average frequency ω log and electron-phonon coupling parameters λ both contribute to the enhancement of T c . For all the three phases at pressures above 2 GPa, T c is found to be primarily determined by λ . Further investigation reveals that for all the three phases, the change in λ with pressure can be explained mainly by change in the phonon frequency. Thus for Ba-II and Ba-V, although they exhibit completely different superconducting behaviors, their superconductivities have the same origin; the pressure dependence of T c is determined finally by the pressure dependence of phonon frequency. 相似文献
10.
采用第一原理方法计算了高压下金属Ba的三个高压相 Ba-I, Ba-Ⅱ和Ba-V的稳定性及热动力学性质.结果表明, Ba的三个高压相在0 K时在其压力范围内都是动力学和力学稳定的;但随压力增加, Ba-I 和Ba-Ⅱ 的声子谱频率出现异常"软化",而Ba-V则出现"硬化".虽然 Ba-Ⅱ 和 Ba-V 同为六方密堆(hcp)结构,计算表明它们在高压下表现出了不同的弹性各向异性.计算同时发现 Ba-Ⅱ 在更高的压力下仍满足力学稳定条件,但声子谱有虚频存在, 表明动力学失稳是Ba-Ⅱ在压力下向Ba-I!V相转变的原因. 计算和比较了同为六方密堆(hcp)结构的Ba-Ⅱ和Ba-V在高压下的声速、 德拜温度、体模量、剪切模量等力学和热学性质, 展现了金属Ba在压力下的稳定机制和热动力学性质. 相似文献