Entanglement Evolution of a Two-Qubit System beyond Rotating-Wave Approximation

Two noninteracting qubits, initially entangled in Bell states, are coupled to a one-mode cavity and evolve under its influence. The entanglement evolution of the two qubits is investigated beyond the rotating-wave approximation. It is shown that the counter-rotating wave terms have a great influence on the disentanglement behavior.     

Bose--Einstein Condensates with Two- and Three-Body Interactions in an Anharmonic Trap at Finite Temperature

The transition temperature, the depletion of the condensate atoms and the collective excitations of a Bose-Einstein condensation （BEC） with two- and three-body interactions in an anharmonic trap at finite temperature are studied in detail. By using the Popov version of the Hartree-Fock-Bogoliubov （HFB） approximation, an extended self-consistent model describing BEC with both two- and three-body interactions in a distorted harmonic potential at finite temperature is obtained and solved numerically. The results show that the transition temperature, the condensed atom number and the collective excitations are modified dramatically by the atomic three-body interactions and the distortion of the harmonic trap.     

A Wide Band Strong Acoustic Absorption in a Locally Network Anechoic Coating

Composite materials with interpenetrating network structures usually exhibit unexpected merit due to the cooperative interaction. Locally resonant phononic crystals （LRPC） exhibit excellent sound attenuation performance based on a periodical arrangement of sound wave scatters. Inspired by the interpenetrating network structure and the LRPC concept, we develop a locally network anechoic coating （LNAC） that can achieve a wide band of underwater strong acoustic absorption. The experimental results show that the LNAC possesses an excellent underwater acoustic absorbing capacity in a wide frequency range. Moreover, in order to investigate the impact of the interpenetrating network structure, we fabricate a faultage structure sample and the network is disconnected by hard polyurethane （PU）. The experimental comparison between the LNAC and the fanltage structure sample shows that the interpenetrating network structure of the LNAC plays an important role in achieving a wide band strong acoustic absorption.     

Implementing a Multi-Qubit Quantum Phase Gate Encoded by Photonic Qubit

A protocol is proposed to implement a three-qubit phase gate for photonic qubits in a three-mode cavity. The idea can be extended to directly implement a N-qubit phase gate. We also show that the interaction time remains unchanged with the increasing number of qubits. In addition, the influence of cavity decay and atomic spontaneous emission on the gate fidelity and photon loss probability is also discussed by numerical calculation.     

Locally Rotationally Symmetric Bianchi Type-I Model with Time Varying Λ Term

We investigate the locally rotationally symmetric (LRS) Bianchi type-I cosmological model for stiff matter and a vacuum solution with a cosmological term proportional to R^-m (R is the scale factor and m is a positive constant). The cosmological term decreases with time. We obtain that for both the cases the present universe is accelerating with a large fraction of cosmological density in the form of a cosmological term.     

Clockwise vs Counter-Clockwise I-V Hysteresis of Point-Contact Metal-Tip/Pr0.7 Ca0.3MnO3/Pt Devices

Metal-tip/Pr0.7Ca0.3MnO3/Pt devices possess two types of I-V hysteresis： clockwise vs counter clockwise depending on the tip materials. The criteria for categorization of these two types of devices can be simply based on whether the Gibbs free energy of oxidation for the metal tip is lower or higher than that of PCMO, respectively. While the clockwise hysteresis can be attributed to electric field induced oxidation/reduction, the counter clockwise hysteresis can be explained by oxygen vacancy migration in an electrical field. Alternating-current conductance spectra also reveal distinct hopping barriers between these two categories of devices at high resistive states.     

The Fractal Dimensions of Complex Networks

It is shown that many real complex networks share distinctive features, such as the small-world effect and the heterogeneous property of connectivity of vertices, which are different from random networks and regular lattices. Although these features capture the important characteristics of complex networks, their applicability depends on the style of networks. To unravel the universal characteristics many complex networks have in common, we study the fractal dimensions of complex networks using the method introduced by Shanker. We find that the average ＇density＇ （p（r ） ） of complex networks follows a better power-law function as a function of distance r with the exponent dl, which is defined as the fractal dimension, in some real complex networks. Furthermore, we study the relation between df and the shortcuts Nadd in small-world networks and the size N in regular lattices. Our present work provides a new perspective to understand the dependence of the fractal dimension df on the complex network structure.     

Coarse-Grained Molecular Dynamics Simulation of a Red Blood Cell

A worm-like chain model based on a spectrin network is employed to study the biomechanics of red blood cells. Coarse-grained molecular dynamics simulations are performed to obtain a stable configuration free of external loadings. We also discuss the influence of two parameters： the average bending modulus and the persistence length. The change in shape of a malaria-infected red blood cell can contribute to the change in its molecular-based structure. As the persistence length of the membrane network in the infected red blood cell decreases, the deformability decreases and the biconcave shape is destroyed. The numerical results are comparable with previously reported experimental results. The coarse-grained model can be used to study the relationship between macro-mechanical properties and molecular-scale structures of cells.     

Improved Quantum Evolutionary Computation Based on Particle SwarmOptimization and Two-Crossovers

A quantum evolutionary computation （QEC） algorithm with particle swarm optimization （PSO） and two-crossovers is proposed to overcome identified limitations. PSO is adopted to update the Q-bit automatically, and two-crossovers are applied to improve the convergence quality in the basic QEC model. This hybrid strategy can effectively employ both the ability to jump out of the local minima and the capacity of searching the global optimum. The performance of the proposed approach is compared with basic QEC on the standard unconstrained scalable benchmark problem that numerous hard combinatorial optimization problems can be formulated. The experimental results show that the proposed method outperforms the basic QEC quite significantly.     

Raman Investigation of Sodium Titanate Nanotubes under Hydrostatic Pressures up to 26.9GPa

High pressure behavior of sodium titanate nanotubes （Na2Ti2O5） is investigated by Raman spectroscopy in a diamond anvil cell （DAC） at room temperature. The two pressure-induced irreversible phase transitions are observed under the given pressure. One occurs at about 4.2 GPa accompanied with a new Raman peak emerging at 834 cm-1 which results from the lattice distortion of the Ti-O network in titanate nanotubes. It can be can be assigned to Ti-O lattice vibrations within lepidocrocite-type （H0.7Ti1.825V0.175O4＆#12539;H2O）TiO6 octahedral host layers with V being vacancy. The structure of the nanotubes transforms to orthorhombic lepidocrocite structure. Another amorphous phase transition occurs at 16.7 GPa. This phase transition is induced by the collapse of titanate nanotubes. All the Raman bands shift toward higher wavenumbers with a pressure dependence ranging from 1.58-5.6 cm-1/GPa.     

A Toy Model for Magnetic Field Configurations in Black Hole Accretion Discs

We discuss the feature of the magnetic field configuration arising from double counter oriented electric currentrings in the accretion disc around a Kerr black hole （BH）. We discuss the relevant physical quantities corresponding to this configuration： （1） the power and torque transferred by the large-scale magnetic field, （2） the angular momentum and energy fluxes transferred from the BIt to the inner disc, （3） the radiation flux from the disc. In addition, we discuss the possibility that the closed magnetic field anchored at the disc probably evolves to the open magnetic field, which is helpful to produce the jet from the disc.     

Another Conserved Quantity by Mei Symmetry of Tzénoff Equation for Non-Holonomic Systems

As a direct result of Mei symmetry of the Ténoff equation for non-holonomic mechanical systems, another conserved quantity is studied. The expression and the determining equations of the above conserved quantity are also presented. Using this method, it is easier to find out conserved quantity than ever. In the last, an example is presented to illustrate applications of the new results.     

An Efficient Control Strategy of Epidemic Spreading on Scale-Free Networks

We present a novel and effective method for controlling epidemic spreading on complex networks, especially on scale-free networks. The proposed strategy is performed by deleting edges according to their significances （the significance of an edge is defined as the product of the degrees of two nodes of this edge）. In contrast to other methods, e.g., random immunization, proportional immunization, targeted immunization, acquaintance immunization and so on, which mainly focus on how to delete nodes to realize the control of epidemic spreading on complex networks, our method is more effective in realizing the control of epidemic spreading on complex networks, moreover, such a method can better retain the integrity of complex networks.     

Mechanical Properties and Anisotropy in PbWO4 Single Crystal

The mechanical properties of PbWO4 （PWO） crystals grown by the vertical Bridgman method are systematically investigated using the microindentation technique. In the present work, the Vickers microhardness Hν, fracture toughness Kc, yield strength σy and friability index Bi of PbWO4 crystals are measured. The Vickers microhardness Hν on the （100） wafer is about 140 MPa, which means that PWO is a little soft＇＇ scintillator. The anisotropy of mechanical properties is also investigated under a steady load of 0.5 kg. The （100） wafer of the crystal exhibits combined mechanical properties more excellent than those of （111） and （001） wafers, and the values of Kc, σy, and Bi are 0.538 MPa＆#12539;m1/2, 51.11 kg/mm2 and 284.96 νm-1/2, respectively.     

Formability and Thermal Stability of Ce62Al15Fe8Co15 Bulk Metallic Glass

The formability and thermal stability of Ce62Al15Fe8Co15 bulk metallic glass （BMG） are studied by x-ray diffraction （XRD） and differential scanning calorimetry. The critical diameter of Ce62Al15Fe8Co15 BMG predicted by the parameter γ is about 3.1 mm, which is roughly in agreement with the XRD results. Stability of the BMG is investigated by means of continuous crystallization diagrams obtained from the extension of the Kissinger and Vogel-Fulcher-Tammann （VFT） equations comparatively. It is found that the dependence of crystallization temperature of the BMG on heating rates follows a nonlinear relationship rather than Kissinger and Lasoka＇s linear fittings. The thermal stability of the BMG is investigated by the VFT equation.     

Comment on Q-Switched Tm：YAG Laser Intracavity-Pumped by a 1064 nm Laser

The paper published in Chin. Phys. Lett. 26 （2009） 124211 reported a Q-switched 2-tim Tm：YAG laser that is intracavity pumped by a Nd： YAG laser with emission at 1.06μm. However, analysis of the experimental setup concludes that only the Nd：YAG laser is Q-switched, and the Tm：YAG laser operates in the free-generation regime. Therefore, Q-switch operation for the 2μm emission wavelength is not realized.     

Quantum ion acoustic solitary waves in electron-ion plasmas: A Sagdeev potential approach

Linear and nonlinear ion acoustic waves are studied in unmagnetized electron-ion quantum plasmas. Sagdeev potential approach is employed to describe the nonlinear quantum ion acoustic waves. It is found that density dips structures are formed in the subsonic region in a electron-ion quantum plasma case. The amplitude of the nonlinear structures remains constant and the width is broadened with the increase in the quantization of the system. However, the nonlinear wave amplitude is reduced with the increase in the wave Mach number. The numerical results are also presented.     

Effect of Particle Number Density on Wave Dispersion in a Two-Dimensional Yukawa System

Effect of the particle number density on the dispersion properties of longitudinal and transverse lattice waves in a two-dimensional Yukawa charged-dust system is investigated using molecular dynamics simulation. The dispersion relations for the waves are obtained. It is found that the frequencies of both the longitudinal and transverse dust waves increase with the density and when the density is sufficiently high a cutoff region appears at the short wavelength. With the increase of the particle number density, the common frequency tends to increase, and the sound speed of the longitudinal wave also increases, but that of the transverse wave remains low.     

Nonlinear Shock and Kink Waves with Complete Coriolis Force in Earth's Atmosphere

Nonlinear waves in a Boussinesq fluid model which includes both the vertical and horizontal components of Coriolis force are studied by using the semi-geostrophic approximation and the method of travelling-wave solution. Taylor series expansion has been employed to isolate the characteristics of the linear Rossby waves and to identify the nonlinear shock and kink waves. The KdV-Burgers and the compound KdV-Burgers equations are derived, their shock wave and kink wave solution are also obtained.     

Parallel velocity shear driven electrostatic waves in a very dense nonuniform magnetoplasma

It is shown that the parallel (magnetic field-aligned) velocity shear can drive the low-frequency (in comparison with the ion gyrofrequency) electrostatic (LF-ES) waves in an ultracold super-dense nonuniform magnetoplasma. By using an electron density response arising from the balance between the electrostatic and quantum Bohm forces, as well as the ion density response deduced from the continuity and momentum equations, a wave equation for the LF-ES waves is derived. In the local approximation, a new dispersion relation is obtained by Fourier transforming the wave equation. The dispersion relation reveals an oscillatory instability of dispersive drift-like modes in super-dense quantum magnetoplasmas.