Dec 2006, Volume 1 Issue 4
    

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  • Continuous variable quantum communication with bright entangled optical beams
    XIE Chang-de, ZHANG Jing, PAN Qing, JIA Xiao-jun, PENG Kun-chi
    2006, 1(4): 383-395. https://doi.org/10.1007/s11467-006-0049-1
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    In this paper, we briefly introduce the basic concepts and protocols of continuous variable quantum communication, and then summarize the experimental researches accomplished by our group in this field. The main features of quantum communication systems used in our experiments are: (1) The bright entangled optical beams with the anticorrelated amplitude quadratures and the correlated phase quadratures that serve as the entanglement resources and (2) The Bell-state direct detection systems are utilized in the measurements of quantum entanglement and transmitted signals instead of the usually balanced homodyne detectors.
  • Negative refraction and focusing of electromagnetic wave through two-dimensional photonic crystals
    ZHANG Xiang-dong
    2006, 1(4): 396-404. https://doi.org/10.1007/s11467-006-0040-x
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    The negative refraction of electromagnetic waves in photonic crystals was recently demonstrated experimentally, and the physical properties were analyzed. Microsuperlenses based on two-dimensional photonic crystals were designed and the subwavelength images were observed. In this review, after providing a brief history of the research related to the above phenomena, we will summarize our research works in this field including the method of creating a negative refraction region, generating an absolute negative refraction, the focusing of unpolarized electromagnetic waves, and the effect of interface and disorder on the image by the two-dimensional photonic crystal flat lens. The discussion on the negative refraction and the focusing by high symmetric quasicrystals is also presented.
  • Theoretical study on single-molecule spectroscopy
    SHAN Guang-cun
    2006, 1(4): 405-411. https://doi.org/10.1007/s11467-006-0053-5
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    The photon-by-photon approach for single molecule spectroscopy experiments utilizes the information carried by each detected photon and allows the measurements of conformational fluctuation with time resolution on a vast range of time scales, where each photon represents a data point. Here, we theoretically simulate the photon emission dynamics of a single molecule spectroscopy using the kinetic Monte Carlo algorithm to understand the underlying complex photon dynamic process of a single molecule. In addition, by following the molecular process in real time, the mechanism of complex biochemical reactions can be revealed. We hope that this theoretical study will serve as an introduction and a guideline into this exciting new field.
  • Solution to causality paradox upon total reflection
    LIU Xiang-min, CAO Zhuang-qi, ZHU Peng-fei, SHEN Qi-shun
    2006, 1(4): 412-418. https://doi.org/10.1007/s11467-006-0044-6
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    A dispute about the existence of an additional time (named as the Goos-Hänchen time) associated with the Goos-Hänchen shift in total reflection has recently arisen. At the same time, an inconsistency between the optical ray model and the electromagnetic theory also appears in the optical planar waveguide. By analyzing light propagation in an optical planar waveguide with both the zigzag-ray model and the electromagnetic theory, this paper shows that the Goos-Hänchen time really exists, and the total time delay upon total reflection upon an ideal nonabsorbing plasma mirror is the sum of the group-delay time and the Goos-Hänchen time. The causality paradox of total reflection of a TM wave upon an ideal nonabsorbing plasma mirror is also solved taking into consideration the negative Goos-Hänchen shift. Finally, the expression of the group velocity of the guided mode in optical planar waveguide was obtained, which clearly shows that the time delay upon total reflection is the sum of the group-delay time and the Goos-Hänchen time at given any time.
  • Hydrogen atom in strong magnetic field: a high accurate calculation in spheroidal coordinates
    LIU Qiang, KANG Shuai, ZHANG Xian-zhou, SHI Ting-yun
    2006, 1(4): 419-423. https://doi.org/10.1007/s11467-006-0045-5
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    A B-spline-type basis set method for the calculation of hydrogen atom in strong magnetic fields in the frame of spheroidal coordinates has been introduced. High accurate energy levels of hydrogen in the magnetic field, with strength ranging from 0 to 1000 a.u., have been obtained. For the ground state, 1s0, energies with at least 11 significant digits have been obtained. For the low-lying excited state, 2 p-1, energies with at least 9 significant digits are obtained. The method has also been applied to the calculation of hydrogen Rydberg states in laboratory magnetic fields. Energy spectra with at least 10 significant digits are presented. A comparison with other results in the literatures has been performed. Our results are comparable to the most accurate one up to date. A possible extension to the cases of parallel and crossed electric and magnetic fields have been discussed.
  • Electron momentum spectroscopy of the highest occupied molecular orbitals of chlorobromomethane
    YANG Xue-feng, WU Fang, SHAN Xu, YAN Mi, WANG Ke-dong, XUE Xin-xia, CHEN Xiang-jun, XU Ke-zun
    2006, 1(4): 424-427. https://doi.org/10.1007/s11467-006-0052-6
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    The first measurement of the complete valence shell binding energy spectra of chlorobromomethane (CH2 BrCl) is reported by (e, 2e) electron momentum spectrometer using symmetric non-coplanar geometry at an impact energy of 1200 eV plus binding energy. The experimental electron momentum profiles of the highest occupied molecular orbitals (HOMOs) are extracted and compared with Hartree-Fock (HF) and density functional theory (DFT) calculations. DFT calculation employing B3LYP hybrid functional and the large-sized basis sets provides the best agreement with the experiment.
  • Current progress on heat conduction in one-dimensional gas channels
    MAO Jun-wen, LI You-quan
    2006, 1(4): 428-441. https://doi.org/10.1007/s11467-006-0048-2
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    We give a brief review of the past development of model studies on one-dimensional heat conduction. Particularly, we describe recent achievements on the study of heat conduction in one-dimensional gas models including the hard-point gas model and billiard gas channel. For a one-dimensional gas of elastically colliding particles of unequal masses, heat conduction is anomalous due to momentum conservation, and the divergence exponent of heat conductivity is estimated as α≈0.33 in κ ∼ Lº. Moreover, in billiard gas models, it is found that exponent instability is not necessary for normal heat conduction. The connection between heat conductivity and diffusion is investigated. Some new progress is reported. A recently proposed model with a quantized degree of freedom to study the heat transport in quasi-one dimensional systems is illustrated in which three distinct temperature regimes of heat conductivity are mani-fested. The establishment of local thermal equilibrium (LTE) in homogeneous and heterogeneous systems is also discussed. Finally, we give a summary with an outlook for further study about the problem of heat conduction.
  • Vertically aligned and hexagonal crystal ZnSe nanoribbon arrays on Zn substrates
    PANG Qi, ZHAO Li-juan, GE Wei-kun, WANG Jian-nong, FANG Yue-ping, WEN Xiao-gang, YANG Shi-he
    2006, 1(4): 442-445. https://doi.org/10.1007/s11467-006-0046-4
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    The vertically aligned and hexagonal ZnSe nanoribbon array can be easily obtained by heating ZnSe: 0.38 en precursors (en = ethylenediamine), while ZnSe precursor nanoribbon arrays are grown directly on Zn foils in en using the solvothermal method. The nanoribbons are mostly about 4 nm in thickness, 100 300 nm in width, and 2 μm in length. The characteristics observed using scanning electron microscopy and X-ray diffraction indicate that the ZnSe precursor as well as ZnSe nanoribbons are vertically aligned on almost the whole zinc foil surface and form a large-scale uniform array. Particularly, ZnSe precursor nanoribbons are hybrid materials of ZnSe and en, while ZnSe nanoribbons are in the from of hexagonal structures. Possible growth mechanisms of the ZnSe precursor nanoribbon arrays are also proposed.
  • MgB2 thick films deposited on stainless steel substrate with Tc higher than 39 K
    LI Fen, GUO Tao, ZHANG Kai-cheng, CHEN Chin-ping, FENG Qing-rong
    2006, 1(4): 446-448. https://doi.org/10.1007/s11467-006-0041-9
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    Thick MgB2 (magnesium diborate) films, ∼ 10 μm, with Tc (onset) = 39.4 K and Tc (zero) = 39.2 K have been successfully grown on a stainless steel substrate using a technique called hybrid physical-chemical deposition (HPCVD). The deposition rate is high, ∼ 6.7 nm /s. The X-ray diffraction (XRD) indicates that it is highly (101) and c-axis oriented. The scanning electron microscope (SEM) images demonstrate that the film grown is in island-mode . The uniform superconducting phase in the film is shown by the M-T measure-ment.
  • Determination of the gravitational constant G
    HU Zhong-kun, LIU Qi, LUO Jun
    2006, 1(4): 449-457. https://doi.org/10.1007/s11467-006-0039-3
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    A precise knowledge of the Newtonian gravitational constant G has an important role in physics and is of considerable meteorological interest. Although G was the first physical constant to be introduced and measured in the history of science, it is still the least precisely determined of all the fundamental constants of nature. The 2002 CODATA recommended value for G, G = (6.6742 ± 0.0010) ? 10-11m3•kg-1•s-2, has an uncertainty of 150 parts per million (ppm), much larger than that of all other fundamental constants. Reviewed here is the status of our knowledge of the absolute value of G, methods for determining G, and recent high precision experiments for determining G.
  • Synchronization on coupled dynamical networks
    ZHENG Zhi-gang, FENG Xiao-qin, AO Bin, Michael C. Cross
    2006, 1(4): 458-467. https://doi.org/10.1007/s11467-006-0047-3
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    In this paper, partial synchronization (PaS) in networks of coupled chaotic oscillator systems and synchronization in sparsely coupled spatiotemporal systems are explored. For the PaS, we reveal that the existence of PaS patterns depends on the symmetry property of the network topology, while the emergence of the PaS pattern depends crucially on the stability of the corresponding solution. An analytical criterion in judging the stability of PaS state on a given network are proposed in terms of a comparison be tween the Lyapunov exponent spectrum of the PaS manifold and that of the transversal manifold. The competition and selections of the PaS patterns induced by the presence of multiple topological symmetries of the network are studied in terms of the criterion. The phase diagram in distinguishing the synchronous and the asynchronous states is given. The criterion in judging PaS is further applied to the study of synchronization of two sparsely coupled spatiotemporal chaotic systems. Different synchronization regimes are distinguished. The present study reveals the intrinsic collective bifurcation of coupled dynamical systems prior to the emergence of global synchronization.
  • Radiative opacity of plasmas studied by detailed term (level) accounting approaches
    ZENG Jiao-long, JIN Feng-tao, YUAN Jian-min
    2006, 1(4): 468-489. https://doi.org/10.1007/s11467-006-0042-8
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    Detailed term and level accounting (DTA and DLA) schemes have been developed to calculate the spectrally resolved and Rosseland and Planck mean opacities of plasmas in local thermodynamic equilibrium. Various physical effects, such as configuration interaction effect (including core-valence electron correlations effect and relativistic effect), detailed line width effect (including the line saturation effect), etc., on the opacity of plasmas have been investigated in detail. Some of these physical effects are less capable or even impossible to be taken into account by statistical models such as unresolved transition arrays, super-transition-array or average atom models. Our detailed model can obtain accurate opacity of plasmas. Using this model, we have systematically investigated the radiative opacities of low, medium and high-Z plasmas under different conditions of temperature and density. For example, for aluminum plasma, in the X-ray region, we demonstrated the effects of autoionization resonance broadening on the opacity for the first time. Furthermore, the relativistic effects play an important role on the opacity as well. Our results are in good agreement with other theoretical ones although better agreement can be obtained after the effects of autoionization resonance broadening and relativity have been considered. Our results also show that the modelling of the opacity is very complicated, since too many physical effects influence the accuracy of opacity. For medium and high-Z plasmas, however, there are systematic discrepancies unexplained so far between the theoretical and experimental opacities. Here, the theoretical opacities are mainly obtained by statistical models. To clarify the discrepancies, efforts from both sides are needed. From the viewpoint of theory, however, a DLA method, in which various physical effects can be taken into account, should be useful in resolving the difference. Taking gold plasma as an example, we studied in detail the effects of core-valence electron correlation and line width on the opacity. Our DLA results correctly explained, for the first time, the relative intensity of the two strong absorption peaks located near the photon energy of 70 and 80 eV, which was experimentally observed by Eidmann et al. [Europhys. Lett., 1998, 44: 459].
  • Multipole effects to the opacity of hot dense gold plasma
    ZENG Lei, JIN Feng-tao, YUAN Jian-min
    2006, 1(4): 490-494. https://doi.org/10.1007/s11467-006-0043-7
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    The contributions of the multipole transitions to the opacity of hot dense gold plasma are taken into account by using an average-atom model. The influences of the E2, E3 and E4 transitions on the Rosseland opacity are studied, respectively. Comparisons with Miao s calculation have been made. It shows that using the Taylor series to account for the multipole transitions is no longer valid since ikr is not much smaller than the unit when the photon energy goes very high.
  • Interaction and resonance phenomena of multi-soliton
    YANG Hong-juan, SHI Yu-ren, DUAN Wen-shan
    2006, 1(4): 495-499. https://doi.org/10.1007/s11467-006-0051-7
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    As is well known, Korteweg-de Vries equation is a typical one which has planar solitary wave. By considering higher order transverse disturbance to planar solitary waves, we study a Kadomtsev-Petviashvili (KP) equation and find some interesting results. In this letter we investigate the three soliton interaction and their resonance phenomena of KP equation, and theoretically find that the maximum amplitude is 9 times of the initial interacting soliton for three same amplitude solitons. Three arbitrary amplitude soliton interaction of KP equation is also studied by numerical simulation, which can also results in resonance phenomena.
  • Effective medium method of slightly compressible elastic media permeated with air-filled bubbles
    QIN Bo, LIANG Bin, ZHU Zhe-min, CHENG Jian-chun
    2006, 1(4): 500-505. https://doi.org/10.1007/s11467-006-0050-8
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    An effective medium method is developed for the slightly compressible elastic media permeated with air-filled bubbles, according to the nonlinear oscillation of the bubble, which happens when compressional wave travels through the porous media. The effective Lame coefficients of the porous medium and the nonlinear elastic wave equation are deduced, based on the fact that the micro-unit of the effective medium should have the same stress and strain as the micro-unit of the porous media. The linearized properties obtained by this method are in good agreement with the results of Gaunaurd s classic theory [Gaunaurd G.C. and ?berall H., J. Acoust. Soc. Am., 1978, 63: 1699 1711]. Furthermore, the nonlinear coefficient, which is an important property of the porous media, can also be acquired by this method.
  • The evolution of opinions on scale-free networks
    GUO Long, CHANG Yun-feng, CAI Xu
    2006, 1(4): 506-509. https://doi.org/10.1007/s11467-006-0054-4
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    An opinion evolution model without bounded confidence  is proposed in this paper. Computer simulation shows that our model can figure out the breakage of the coexistence of majority and minority after a period s evolution. With further analysis, our model shows that, without the influence of the external field, the opinions will finally die out to a limited small value no matter what the initial condition of the system is. On the other hand, we simulate the evolution of the opinions under the influence of an external field, and get some meaningful and instructional results.