Current Issue

Volume 17 Issue 10
Online Date:
Previous Issue    Next Issue
Original Articles
Teleportation of an Unknown Quantum State via Partly Entangled States
FENG Xun-Li, GONG Shang-Qing, WANG Zhong-Yang, XU Zhi-Zhan
Chin. Phys. Lett. 2000, 17 (10): 703-704 .  
Abstract   PDF(pc) (160KB) ( 364 )
The teleportation of an unknown quantum state from one observer to another is of great importance in quantum information. In the standard teleportation scheme, a maximally entangled state is demanded. However, it is difficult to prepare such states in practice, and real entangled states are always partly entangled. We present a scheme to teleport an unknown quantum state using two partly entangled states. We show that the teleportation can be realized with a certain probability.

Quantum Statistical Entropy of Spherical Black Holes in Higher Dimensions
XU Dian-Yan
Chin. Phys. Lett. 2000, 17 (10): 705-707 .  
Abstract   PDF(pc) (197KB) ( 829 )
The free energy and entropy of a general spherically symmetry black hole are calculated by quantum statistic method with brick wall model. Two different kinds of approximation are used to calculate the number of states in transverse spatial space. The final results are approximately equal except a rational numerical constant. The formulas of free energy and entropy, evaluated by each one of the two different kinds of approximation, are the same except some numerical constants. The free energy and entropy are dependent on the spacetime dimensions D. When D = 4, they reduce to the usual well known results.
Diffusion in a Symplectic Map with Application to Asteroid Motion
ZHOU Li-Yong, SUN Yi-Sui, ZHOU Ji-Lin
Chin. Phys. Lett. 2000, 17 (10): 708-710 .  
Abstract   PDF(pc) (243KB) ( 365 )
In studying a 2-dimensional syrnplectic map, the exponential law and algebraic law are observed in the diffusion of orbits in the phase space. The diffusion time in the vicinity of an island is investigated carefully and a logarithm law is found for the first time. The distribution of asteroids in the main belt and the diffusion velocities in 3:2 and 4:3 resonances are discussed using this map.
Behavior of the Lyapunov Exponent and Phase Transition in Nuclei
WANG Nan, WU Xi-Zhen, LI Zhu-Xia, , WANG Ning, ZHUO Yi- Zhong, , SUN Xiu-Quan
Chin. Phys. Lett. 2000, 17 (10): 711-713 .  
Abstract   PDF(pc) (301KB) ( 440 )
Based on the quantum molecular dynamics model, we investigate the dynamical behaviors of the excited nuclear system to simulate the latter stage of heavy ion reactions, which associate with a liquid-gas phase transition. We try to search a microscopic way to describe the phase transition in real nuclei. The Lyapunov exponent is employed and examined for our purpose. We find out that the Lyapunov exponent is one of good microscopic quantities to describe the phase transition in hot nuclei. Coulomb potential and the finite size effect may give a strong influence on the critical temperature. However, the collision term plays a minor role in the process of the liquid-gas phase transition in finite systems.

Nonlinear Permittivity Including Non-Abelian Self-Interaction of Plasmons in Quark-Gluon Plasma
CHEN Ji-Sheng, ZHENG Xiao-Ping, LI Jia-Rong
Chin. Phys. Lett. 2000, 17 (10): 714-716 .  
Abstract   PDF(pc) (239KB) ( 413 )
By decomposing the distribution functions and color field to regular and fluctuation parts, the solution of the semi-classical kinetic equations of quark-gluon plasma is analyzed. Through expanding the kinetic equations of the fluctuation parts to third order, the nonlinear permittivity including the self-interaction of gauge field is obtained and a rough numerical estimate is given out for the important k = 0 modes of the pure gluon plasma.
Deformed Relativistic Hartree Theory in Coordinate Space and in Harmonic Oscillator Basis
ZHOU Shan-Gui, , MENG Jie, , Shuhei YAMAJI, YANG Si-Chun,
Chin. Phys. Lett. 2000, 17 (10): 717-719 .  
Abstract   PDF(pc) (247KB) ( 456 )
The deformed relativistic Hartree theory (DRH) is solved both in coordinate space (DRH-c) and in harmonic oscillator basis (DRH-o). Results obtained from these two methods are compared in details. The DRH-c and DRH-o calculations give similar total binding energies, deformation, level structures and radii for nitrogen iso-topes, while their descriptions on the density distributions for drip-line nuclei are very different. The large spatial distributions of nucleon densities, which is crucial to understand a weakly bound system, can only be obtained by DRH-c calculations. This implies that the DRH theory should be solved in coordinate space in order to describe nuclei close to the drip line.
A Possible New Effect of Self-Consistency in the Relativistic Hartree-Fock Approximation
YAO Yu-Jie, ZHANG Hai-Xia, ZHU Jiang-Ming, LIU Guang-Zhou, WU Shi-Shu
Chin. Phys. Lett. 2000, 17 (10): 720-722 .  
Abstract   PDF(pc) (246KB) ( 404 )
A new effect of self-consistency in the relativistic Hartree-Fock (HF) approximation suggested previously is confirmed by a renormalized calculation with the on-shell renormalization conditions. Two self-consistency schemes, one requiring self-consistency in the HF potential (scheme P) and the other in the baryon propagator (scheme BP), are studied. It is pointed out that the on-shell renormalization conditions make the self-consistency requirement in scheme P automatically satisfied. Our calculated results show that scheme P is a good approximation to scheme BP for the calculation of the baryon propagator and the self-consistency in scheme BP diminishes the continuum part of the spectral representation for the baryon propagator, while scheme P yields a baryon propagator which is the same as the HF result contributed by the single particle part of the above spectral representation alone. Further, it is demonstrated that the region of validity of the quasi-particle approximation may depend on the renormalization conditions.
High-Order Harmonic Generation in the Ionization Process
CHEN Jing, CHEN Shi-Gang, LIU Jie
Chin. Phys. Lett. 2000, 17 (10): 723-725 .  
Abstract   PDF(pc) (234KB) ( 336 )
Based on the nonperturbative quantum electrodynamics scattering theory for multiphoton ionization developed recently, high-order harmonic generated in the ionization process is discussed. The influence of the Coulomb potential is treated as a perturbation in the expansion of the transition matrix. It is deduced that the harmonic photons are emitted in the resonant process during ionization and the width of the harmonic peaks is just the ionization rate of the atom.
Fourth-Order Interference in Femtosecond Spontaneous Parametric Down-Conversion
JIANG Yun-Kun, SHI Bao-Sen, LI Jian, FAN Xiao-Feng, GUO Guang-Can
Chin. Phys. Lett. 2000, 17 (10): 726-727 .  
Abstract   PDF(pc) (177KB) ( 349 )
We report a fourth-order interference experiment in which pairs of photons are produced in spontaneous parametric down-conversion pumped by femtosecond pulses interfere in a Hong-Ou-Mandel interferometer. The visibility of the interference is (64±4)%, exceeding the bound of 50% predicted by classical interference theory.
Single-Frequency Nd:YAG Ring Lasers with Corner Cube Prism
WU Ke-Ying, YANG Su-Hui, ZHAO Chang-Ming, WEI Guang-Hui
Chin. Phys. Lett. 2000, 17 (10): 728-730 .  
Abstract   PDF(pc) (193KB) ( 595 )
We put forward another form of the non-planar ring lasers, in which the corner cube prism is the key element and the Nd:YAG crystal is used as a Porro prism to enclose the ring resonator. The phase shift due to the total internal reflections of the three differently orientated reflection planes of the corner cube prism, Faraday rotation in the Nd:YAG crystal placed in a magnetic field and the different output coupling in S and P polarization form an optical diode and enforce the single-frequency generating power. A round trip analysis of the polarization properties of the resonator is made by the evaluation of Jones matrix.
Small-Scale Self-Focusing of Intense Laser Beams In the Presence of Vector Effect
WEN Shuang-Chun, FAN Dian-Yuan
Chin. Phys. Lett. 2000, 17 (10): 731-733 .  
Abstract   PDF(pc) (212KB) ( 467 )
We extend Bespalov-Talanov (B-T) theory on small-scale self-focusing (SSSF) to include vector effect of a very narrow intense laser beam with application of the vector self-focusing model. The gain spectrum for perturbations is obtained by using the standard linear instability analysis. It is shown that the influence on SSSF of vector effect is closely related to the beam width. For a very narrow beam, the role played by vector effect becomes significant, it reduces the fastest growing frequency and the maximum growth rate, and shortens the frequency range for perturbation growing, and thus deviates the gain spectrum from that of B-T theory.
A Schrödinger Formulation for Paraxial Light Beam Propagation and Its Application to Propagation through Nonlinear Parabolic-Index Media
LIU Cheng-Yi, GUO Hong, HU Wei, DENG Xi-Ming
Chin. Phys. Lett. 2000, 17 (10): 734-736 .  
Abstract   PDF(pc) (253KB) ( 580 )
The Helmholtz equation is reduced to the Schrödinger-like equation and then the quantities representing the gross features for a paraxial optical beam, such as the width, divergence, radius of curvature of the wave front, complex beam parameter, beam quality factor, and the potential function representing beam propagation stability, are studied by using the quantum mechanical methods. The results derived in other ways previously are rederived by our formulation in a more systematical and explicit fashion analytically, and some new results are demonstrated. The general equations for the evolution of these quantities, i.e., the first- and second-order differential equations with respect to the propagation distance, such as the universal formula for the width and curvature radius, the general formula for the first derivative of the complex beam parameter with respect to the axial coordinate, the general formula for the second derivative of the width with respect to the axial coordinate, and some general criteria for the conservation of the beam quality factor and the existence of a potential well of the potential function, are derived. We also discuss the application of our formulation to nonlinear parabolic-index media.
Analysis of Higher Order Channel Dropping Tunneling Processes in Photonic Crystals
FU Jian, HE Sai-Ling
Chin. Phys. Lett. 2000, 17 (10): 737-739 .  
Abstract   PDF(pc) (248KB) ( 377 )
A theoretical analysis is given for a higher order channel drop tunneling structure composed of two horizontal channels and a resonator system with two vertical multi-mode cavities in a two- or three-dimensional photonic crystal. Criteria for a complete transfer are derived for the application of wavelength division multiplexing. Compared to the resonator system with two single-mode cavities or a single multi-mode cavity, the present resonator system improves the transport properties.
Microstructure Effects of Ultrasonic Waves in a Fiber Reinforced Composite Plate
HAN Jun-Bo, TANG Li-Guo, CHENG Jian-Chun, Yves Berthelot
Chin. Phys. Lett. 2000, 17 (10): 740-742 .  
Abstract   PDF(pc) (251KB) ( 373 )
The microstructure effect of ultrasonic waves in a unidirectional titanium graphite composite is analyzed by the mode energy conversions of the laser-generated ultrasonic Lamb waves. The carrying energy of each mode in the Lamb waves is calculated quantitatively by the time-frequency filtering technique of the Wigner distribution. We found that the energy conversions among modes have happened in the process of propagation of ultrasonic Lamb wave. These energy conversions are attributed to microstructure scattering of ultrasonic wave by the fibers in a fiber reinforced composite material. This work will provide a quantitative method of ultrasonic characterization of microstructure feature of the composite materials by the laser-generated Lamb wave technique.
Lattice Boltzmann Model for Compressible Fluid on a Square Lattice
SUN Cheng-Hai
Chin. Phys. Lett. 2000, 17 (10): 743-745 .  
Abstract   PDF(pc) (212KB) ( 485 )
A two-level four-direction lattice Boltzmann model is formulated on a square lattice to simulate compressible flows with a high Mach number. The particle velocities are adaptive to the mean velocity and internal energy. Therefore, the mean flow can have a high Mach number. Due to the simple form of the equilibrium distribution, the 4th order velocity tensors are not involved in the calculations. Unlike the standard lattice Boltzmann model, no special treatment is need for the homogeneity of 4th order velocity tensors on square lattices. The Navier-Stokes equations were derived by the Chapman-Enskog method from the BGK Boltzmann equation. The model can be easily extended to three-dimensional cubic lattices. Two-dimensional shock-wave propagation was simulated.
Quasistatic Magnetic Field Generation by an Intense Ultrashort Laser Pulse in Underdense Plasma
ZHENG Chun-Yang, ZHU Shao-Ping, HE Xian-Tu
Chin. Phys. Lett. 2000, 17 (10): 746-748 .  
Abstract   PDF(pc) (334KB) ( 482 )
The quasistatic magnetic field created in the interaction of intense ultrashort laser pulses with underdense plasmas has been investigated by two-dimensional particle simulation. The relativistic ponderomotive force and plasma wave excited in self-modulation processes can drive intense electron current mainly in the propagation direction. As a result, an azimuthal, multi-mega Gauss order quasi-static magnetic field can be generated around the laser beam.
Magnetic-Field-Induced Weak Order in Nematic Liquid Crystals Formed by Biaxial Molecules
ZHANG Zhi-Dong, ZHANG De-Xian, SUN Yu-Bao
Chin. Phys. Lett. 2000, 17 (10): 749-751 .  
Abstract   PDF(pc) (222KB) ( 499 )
Nematic liquid crystal system of interacting biaxial particles via dispersion forces is studied. The molecular orienting potential form in a magnetic field is given for the first time. Weakly ordered isotropic phase is treated in the two-particle cluster approximation. Taking account of the molecular biaxiality, it is found that the ratio of the lowest supercooling temperature T* to the nematic-isotropic phase transition temperature Tc approaches the observed value, and the validity of the mean field theory is clarified.
Rules for Identifying the Magic Angular Momenta of Quantum Dots in a Strong Magnetic Field
RUAN Wen-Ying, LI Quan, CHEN Guo-Sen, HE Hao-Pei, PAN Yu-Bin
Chin. Phys. Lett. 2000, 17 (10): 752-754 .  
Abstract   PDF(pc) (281KB) ( 411 )
In quantum dots under a strong magnetic field, all the electrons occupy only the lowest Landau level and are spin polarized. When an orbiting electron is regarded as a quasiparticle, the interaction between a pair of quasiparticles is a short range attraction matched to a long range repulsive tail. Magic numbers of angular momentum are just those where the quasiparticles can be arranged into compact clusters with their sizes determined by the saturation of the short range attraction.

Optical Properties of Self-organized PbS Quantum Dot Superlattices
YE Chang-Hui, YAO Lian-Zeng, MU Ji-Mei, SHI Gang, ZHANG Li-De
Chin. Phys. Lett. 2000, 17 (10): 755-756 .  
Abstract   PDF(pc) (253KB) ( 455 )
Self-organization of PbS into quantum dot superlattices has been demonstrated for the first time, and hexaplanar colloidal crystals 1-10μm in size made from PbS quantum dots 3-6 nm in diameter are revealed in transmission electron microscope micrographs, and the inner structures of the superlattices can be seen by a high resolution transmission electron microscopy The optical absorption and photoluminescence spectra have been recorded. The ordering of the superlattices is crucial for the understanding of the fundamental properties of quantum-dot arrays, as well as for their optimal utilization in optical and electronic applications.
Dissipation Power of a Disk-Shaped Superconducting Thin Film Along Its Virgin Magnetization Curves
Sahr A. Aruna, YAO Xi-Xian
Chin. Phys. Lett. 2000, 17 (10): 757-759 .  
Abstract   PDF(pc) (162KB) ( 381 )
Based on the Bean critical state model j≤ jc, for both longitudinal and transverse geometry, the total dissipation power P along the virgin magnetization curves is calculated. The dissipation power obtained from the corresponding magnetic measurements for a disk-shaped YBa2Cu3O7-σ thin film in a perpendicular magnetic field is verified. The virgin magnetization curves for the sample at different temperatures are calculated.
Power Law Behavior of the Zero Bias Tunneling Conductance: the New Evidence for d-Wave Symmetry
LI Shao-Xiong, TAO Hong-Jie, XUAN Yi, ZHAO Bai-Ru, ZHAO Zhong-Xian
Chin. Phys. Lett. 2000, 17 (10): 760-762 .  
Abstract   PDF(pc) (199KB) ( 378 )
We report temperature-dependent behavior of the zero bias tunneling conductance (ZBTC), derived from tunneling spectroscopies on as-grown Bi2Sr2CaCu2O8+δ (Bi2212) single crystals taken with evaporated Zn and Pb planar junctions. At Tc the measured ZBTC shows a kink which gives an in situ measure of the superconducting transition temperature (Tc). Below Tc, the T2 dependence of the ZBTC has been observed repeatedly as a new evidence of the d-wave symmetry in Bi2212.



Breakdown of Superconductivity in Small Metallic Grains
CHEN Zhi-Qian, ZHENG Ren-Rong,
Chin. Phys. Lett. 2000, 17 (10): 762-764 .  
Abstract   PDF(pc) (212KB) ( 430 )
Superconductivity in small metallic grains is carefully checked as their size is decreased to a few nm when the average level spacing d could be compared with the bulk gap Δ. Using random matrix theory to the mean field, we find that the average theoretical values of the critical level spacing for both odd and even numbers of electrons and the transition temperature Tc in three Gauss ensembles are quite different for those from the model of uniformly spaced levels. For Sz = 1/2, as grain size is reduced, the transition temperature or the granular gap decreases monotonously, and the relation 2Δ ( 0 ) /кB Tc≤ 3.53 always exists.




Magnetocrystalline Anisotropy and Exchange Interaction in YCo12-xTix Compounds
WANG Jian-Li, TANG Ning, YANG Dong, YANG Chang-Ping, BAO Fu-Quan, SHEN Yu-Ping, WU Guang-Heng, YANG Fu-Ming, E. Brück, F.R. de Boer
Chin. Phys. Lett. 2000, 17 (10): 765-767 .  
Abstract   PDF(pc) (280KB) ( 460 )
Magnetic and structural properties of YCo12-xTixcompounds have been investigated by x-ray diffraction and magnetic measurements. X-ray diffraction patterns of aligned powder samples indicate that the easy magnetization direction at room temperature is along the c-axis for all the compounds. The lattice parameters increase monotonously while Curie temperature TC decreases with increasing Ti content. It was found that all the compounds investigated are strong ferromagnets by analysis of magnetic moments using a magnetic valence model. The values of anisotropy fields Ba at room temperature and 1.5K decrease with increasing x. The easy-axis anisotropy of the YCo12-xTixcompounds is mainly contributed by the Co atoms at 8i sites according to the individual-site-anisotropy model.
Investigation on Photoluminescence of Ordered Structure in the (AIxGal-x)0.51In0.49P(x = 0.29) Alloys
LU Yi-Jun, GAO Yu-Lin, ZHENG Jian-Sheng
Chin. Phys. Lett. 2000, 17 (10): 768-769 .  
Abstract   PDF(pc) (197KB) ( 342 )
The temperature-dependent and excitation-intensity-dependent photoluminescence(PL) spectra are applied to investigate the quaternary (AIxGal-x)0.51In0.49P(x = 0.29)alloys lattice-matched to GaAs. The PL peak is excitation intensity independent, but shows anomalous temperature behavior, where PL peak energy changes with temperature, exhibiting Z-shape dependence. The PL peak energy decreases with increasing temperature from 19K, a blue-shift of PL peak energy occurs between 55K and 84K, afterwards, the PL peak energy decreases monotonously again. This confirms the existence of ordered structure caused by superlattice effect in the (AIxGal-x)0.51In0.49P(x = 0.29)alloys.
Photoluminescence of Polycrystalline SiC Sintered from Graphite and Si Melt
CHEN Zhi-Ming, MA Jian-Ping, WANG Jian-Nong, LU Gang, YU Ming-Bin, LEI Tian-Min, GE Wei-Kun
Chin. Phys. Lett. 2000, 17 (10): 770-772 .  
Abstract   PDF(pc) (249KB) ( 409 )
Intense wide-band photoluminescence (PL) with high stability to ultraviolet (UV) light irradiation has been observed in a wide temperature range from a polycrystalline SiC sintered from graphite and melt Si at high temperature over 1500°C. X-ray diffraction results showed that the sintered material consists of mainly cubic and 6H-SiC crystallites oriented randomly and a small amount of graphite with (002) preferential orientation. PL spectra of the samples were measured under excitation of the incident UV light beam from an He-Cd laser (325 nm, 10mW) in the temperature range from 10 to 300 K. The PL spectra were found to be a single wide-band centered around 2.2 eV at room temperature and to be divided into a much more intensive blue band and a less intensive red band at low temperature. The low temperature PL bands consist of several luminescence peaks that change in intensities relatively with variation of temperature.
Carrier-Transporting and Blue Electroluminescence Properties of a Novel Pyrazoline Derivative
LU Zhi-Yun, YUAN Tong-Suo, ZHU Wei-Guo, LIU Yu, WEI Xiao-Qiang, XIE Ming-Gui, QIU Yong, GAO Yu-Di
Chin. Phys. Lett. 2000, 17 (10): 773-774 .  
Abstract   PDF(pc) (190KB) ( 533 )
A novel compound of pyrazoline derivative, 3-(4-methoxyphenyl)-5-[4-(1,1-dimethylethylpheny1)]-4,5-dihydro-1-Phenyl 1H-Pyrazole (PYZ) has been synthesized. It has a good photoluminescence property and could give blue A uorescence. Four devices have been fabricated to study the carrier-transporting and electroluminescence properties of PYZ. The results indicate that PYZ is a good blue electroluminescent material. The emission peak is observed at 449nm and the half bandwidth is about 80nm, showing that it could emit pure blue light. As to carrier-transporting property, PYZ is found to have electron-transporting ability besides its excellent hole-transporting ability.



Computational Analysis of the Vertical Bridgman Growth of Te Doped GaSb Under Microgravity
LIU Yong-Cai, CHEN Wan-Chun, GE Pei-Wen, HUO Chong-Ru
Chin. Phys. Lett. 2000, 17 (10): 775-777 .  
Abstract   PDF(pc) (272KB) ( 508 )
A transient analysis of Te doped GaSb melt growth process is performed using finite element method. The solute concentration at the growth interface increases with time because of k < 1. The growth interface shape becomes a little flat at the beginning of the growth compared with the initial shape. Radial segregation occurs even under the μg condition. This segregation increases with the increase of gravity when gravity is small, and reaches a maximum at g = 10-3 for our system.
Afterglows from Jetted Gamma-Ray-Burst Remnant: Does the Light Curve Break?
HUANG Yong-Feng, DAI Zi-Gao, LU Tan,
Chin. Phys. Lett. 2000, 17 (10): 778-780 .  
Abstract   PDF(pc) (237KB) ( 436 )
Afterglows from jetted gamma-ray bursts are generally believed to be characterized by an obvious break in the light curve at the relativistic stage. We show that it is not the case. However, an obvious break does exist at the transition from the relativistic phase to the non-relativistic phase. Although this break itself is parameter-dependent, afterglows from jetted remnant are uniformly characterized by a quick decay during the non-relativistic phase.

28 articles