2013年, 第59卷, 第01期　
刊出日期：2013-01-15

  

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  Multifractal Detrended Fluctuation Analysis of Interevent Time Series in a Modified OFC Model

  林敏, 颜双喜, 赵钢, 王刚

  理论物理通讯. 2013, 59(01): 1-6.

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  We use multifractal detrended fluctuation analysis (MF-DFA) method to investigate the multifractal behavior of the interevent time series in a modified Olami-Feder-Christensen (OFC) earthquake model on assortative scale-free networks. We determine generalized Hurst exponent and singularity spectrum and find that these fluctuations have multifractal nature. Comparing the MF-DFA results for the original interevent time series with those for shuffled and surrogate series, we conclude that the origin of multifractality is due to both the broadness of probability density function and long-range correlation.
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  Perfect Single Qubit Mirroring Effects on Two and Three Maximally Entangled Qubits

  M. Ávila

  理论物理通讯. 2013, 59(01): 7-10.

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  Perfect quantum state mirroring in a chain of N spins is defined as the condition in which the state |i> of the chain is swapped into the state |N-i> within a time evolution interval τ. Such a phenomenon is an interesting way of transfering entanglement. An expressions for the perfect mirroring of a single qubit contained in a spin chain were proposed in the past. We exploit such an expressions for calculating the evolution times in chains of both two and three spins. In the case of a chain of two qubits, we derive conditions under which the associated four Bell states diagonalize the Hamiltonian. It is found that for the two Bell states |Φ⁺> and |Φ^->, perfect mirroring does not occur (i.e. entanglement is not preserved under swapping). On the other hand, perfect single qubit mirror effect (entanglement preservation) indeed occurs for the other two Bell states |Ψ⁺> and |Ψ^-> which are mapped into |Φ⁺> and |Φ^-> respectively. For the case of a chain of three qubits, the effects of a perfect single qubit mirroring on a set of four maximally entangled three qubit states ψ₁, ψ₂, χ₁, and χ₂ are studied. Due to the fact that quantum mirroring preserves maximal entanglement, the states ψ₁ and ψ₂ are not altered. However, quantum mirroring changes the states χ₁ and χ₂ only if we apply perfect quantum state mirroring in the site a=1 of the three qubits spin chain. The above constrains the preservation of maximal entanglement under qubit mirroring of such a state. Due to the fact that swapping has already been experimentally tested, a posible experimental implementations of single qubit mirroring is possible.
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  Non-Geometric Conditional Phase Gate by Quantum Zeno Dynamics in Laser-Excited Nitrogen-Vacancy Centers

  苏万钧, 沈利托, 吴怀志, 林秀

  理论物理通讯. 2013, 59(01): 11-16.

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  Based on the quantum Zeno dynamics, we propose a two-qubit non-geometric conditional phase gate between two nitrogen-vacancy centers coupled to a whispering-gallery mode cavity. The varying phases design of periodic laser can be used for realizing non-geometric conditional phase gate, and the cavity mode is virtually excited during the gate operation. Thus, the fidelity of the gate operation is insensitive to cavity decay and the fluctuation of the preset laser intensity. The numerical simulation with a realistic set of experimental parameters shows that the gate fidelity 0.987 can be within reached in the near future.
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  Dynamics of Measurement-Induced Disturbance for a Qubit-Qutrit System in Noninertial Frames

  袁浩, 韦联福

  理论物理通讯. 2013, 59(01): 17-21.

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  We investigate the dynamics of measurement-induced disturbance (MID) for a qubit-qutrit system in noninertial frames under various multi-local decoherence channels (i.e., dephasing, phase-flip, bit-(trit-) flip, bit-(trit-) phase-flip, and depolarizing channels). We find that, for any acceleration, the MID can decay in a monotonic way to zero or to a nonzero steady value (i.e., residual MID exists). Consequently, no sudden death of the MID occurs, which is different from entanglement.
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  On Models of Nonlinear Evolution Paths in Adiabatic Quantum Algorithms

  孙杰, 路松峰, Samuel L. Braunstein

  理论物理通讯. 2013, 59(01): 22-26.

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  In this paper, we study two different nonlinear interpolating paths in adiabatic evolution algorithms for solving a particular class of quantum search problems where both the initial and final Hamiltonian are one-dimensional projector Hamiltonians on the corresponding ground state. If the overlap between the initial state and final state of the quantum system is not equal to zero, both of these models can provide a constant time speedup over the usual adiabatic algorithms by increasing some another corresponding "complexity". But when the initial state has a zero overlap with the solution state in the problem, the second model leads to an infinite time complexity of the algorithm for whatever interpolating functions being applied while the first one can still provide a constant running time. However, inspired by a related reference, a variant of the first model can be constructed which also fails for the problem when the overlap is exactly equal to zero if we want to make up the "intrinsic" fault of the second model——an increase in energy. Two concrete theorems are given to serve as explanations why neither of these two models can improve the usual adiabatic evolution algorithms for the phenomenon above. These just tell us what should be noted when using certain nonlinear evolution paths in adiabatic quantum algorithms for some special kind of problems.
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  Counterfactual Quantum Deterministic Key Distribution

  张盛, 王剑, 唐朝京

  理论物理通讯. 2013, 59(01): 27-31.

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  We propose a new counterfactual quantum cryptography protocol concerning about distributing a deterministic key. By adding a controlled blocking operation module to the original protocol [T.G. Noh, Phys. Rev. Lett. 103 (2009) 230501], the correlation between the polarizations of the two parties, Alice and Bob, is extended, therefore, one can distribute both deterministic keys and random ones using our protocol. We have also given a simple proof of the security of our protocol using the technique we ever applied to the original protocol. Most importantly, our analysis produces a bound tighter than the existing ones.
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  Efficient Polarization Entanglement Distribution for W State Assisted by Frequency Degree of Freedom

  李艳, 陈晓, 曾志, 李熙涵

  理论物理通讯. 2013, 59(01): 32-36.

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  We present an efficient faithful polarization entanglement distribution protocol for W state over an arbitrary noise channel, which use the frequency degree of freedom to carry the entanglement during the transmission. We describe the transmission of three-photon W state as an example, and then generalize this scheme to n-qubit W state situation. The remote parties can obtain maximally entangled W states on the polarization of photons, and the success probability is 100% in principle. As there was few entanglement purification for W state, our scheme is an efficient and practical method to share W state entanglement between distant parties, which will be useful in quantum communication. We also show that our scheme can be used to distribute arbitrary multi-particle entangled state.
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  Quantum Message Distribution

  罗明星, 陈秀波, 邓云, 杨义先

  理论物理通讯. 2013, 59(01): 37-42.

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  The semiquantum techniques have been explored recently to bridge the classical communications and the quantum communications. In this paper, we present one scheme to distribute the messages from one quantum participate to one weak quantum participate who can only measure the quantum states. It is proved to be robust by combining the classical coding encryption, quantum coding and other quantum techniques.
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  String Cosmological Solutions with O(d,d) Duality Symmetry and Matter Coupling

  李宝霖, 颜骏

  理论物理通讯. 2013, 59(01): 43-46.

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  The duality properties of string cosmology model with negative energy matter are investigated by means of renormalization group equation, the cosmological solutions with exotic matter coupling are obtained in D=d+1 dimensional space-time. These inflation-power solutions can describe accelerated and decelerated process in the early universe, and the duality solutions can be generated through O(d,d) transformations.
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  R-mode Instability of Neutron Star with Non-Newtonian Gravity

  燕晶, 文德华

  理论物理通讯. 2013, 59(01): 47-52.

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  The Chandrasekhar-Friedmann-Schutz (CFS) instabilities of r-modes for canonical neutron stars (1.4 M_Θ) with rigid crusts are investigated by using an equation of state of asymmetric nuclear matter with super-soft symmetry energy, where the non-Newtonian gravity proposed in the grand unification theories is also considered. Constrained by the observations of the masses and the spin frequencies for neutron stars, the boundary of the r-mode instability window for a canonical neutron star is obtained, and the results show that the observed neutron stars are all outside the instability window, which is consistent with the theoretical expectation. In addition, an upper limit of the non-Newtonian gravity parameters is also given.
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  Discrete Opinion Dynamics on Online Social Networks

  胡艳丽, 白亮, 张维明

  理论物理通讯. 2013, 59(01): 53-58.

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  This paper focuses on the dynamics of binary opinions {+1,-1} on online social networks consisting of heterogeneous actors. In our model, actors update their opinions under the interplay of social influence and self-affirmation, which leads to rich dynamical behaviors on online social networks. We find that the opinion leading to the consensus features an advantage of the initially weighted fraction based on actors' strength over the other, instead of the population. For the role of specific actors, the consensus converges towards the opinion that a small fraction of high-strength actors hold, and individual diversity of self-affirmation slows down the ordering process of consensus. These indicate that high-strength actors play an essential role in opinion formation with strong social influence as well as high persistence. Further investigations show that the initial fraction of high-strength actors to dominate the evolution depends on the heterogeneity of the strength distribution, and less high-strength actors are needed in the case of a smaller exponent of power-law distribution of actors' strength. Our study provides deep insights into the role of social influence and self-affirmation on opinion formation on online social networks.
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  Cellular Automata Model for Elastic Solid Material

  董银峰, 张广财, 许爱国, 甘延标

  理论物理通讯. 2013, 59(01): 59-67.

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  The Cellular Automaton (CA) modeling and simulation of solid dynamics is a long-standing difficult problem. In this paper we present a new two-dimensional CA model for solid dynamics. In this model the solid body is represented by a set of white and black particles alternatively positioned in the x- and y-directions. The force acting on each particle is represented by the linear summation of relative displacements of the nearest-neighboring particles. The key technique in this new model is the construction of eight coefficient matrices. Theoretical and numerical analyses show that the present model can be mathematically described by a conservative system. So, it works for elastic material. In the continuum limit the CA model recovers the well-known Navier equation. The coefficient matrices are related to the shear module and Poisson ratio of the material body. Compared with previous CA model for solid body, this model realizes the natural coupling of deformations in the x- and y-directions. Consequently, the wave phenomena related to the Poisson ratio effects are successfully recovered. This work advances significantly the CA modeling and simulation in the field of computational solid dynamics.
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  Interaction Behaviors Between Special Dromions in the (2+1)-Dimensional Broer-Kaup-Kupershmidt Equation

  陈未路, 张雯婷, 张立溥, 戴朝卿

  理论物理通讯. 2013, 59(01): 68-72.

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  A modified mapping method is used to obtain variable separation solution with two arbitrary functions of the (2+1)-dimensional Broer-Kaup-Kupershmidt equation. Based on the variable separation solution and by selecting appropriate functions, we discuss the completely elastic head-on collision between two dromion-lattices, non-completely elastic "chase and collision" between two multi-dromion-pairs and completely non-elastic interaction phenomenon between anti-dromion and dromion-pair.
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  Peakon Solutions to Supersymmetric Camassa-Holm Equation and Degasperis-Procesi Equation

  罗琳, 夏宝强, 曹玉峰

  理论物理通讯. 2013, 59(01): 73-79.

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  In this paper, the supersymmetric Camassa-Holm equation and Degasperis-Procesi equation are derived from a general superfield equations by choosing different parameters. Their peakon-type solutions are shown in weak sense. At the same time, the dynamic behaviors are analyzed particularly when the two peakons collide elastically, and some results are compared with each other between the two equations.
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  Motion of Relativistic Strings on the Equatorial Plane in the Schwarzschild Space-Time

  孔德兴, 李晓燕

  理论物理通讯. 2013, 59(01): 80-86.

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  In this paper, we investigate the basic equations of the motion for relativistic strings on the equatorial plane in the Schwarzschild space-time, discuss smooth solutions of the motion equations for closed strings, and obtain some interesting physical results.
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  Top Quark Polarization and Spin Correlation in the Littlest Higgs Model with T-Parity at the ILC

  杨炳方, 李向东

  理论物理通讯. 2013, 59(01): 87-94.

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  In the framework of the littlest Higgs model with T-parity (LHT), we study the top quark spin correlation and polarization at the International Linear Collider (ILC). We find that the top quark polarization asymmetry δ P_t and the left-right asymmetry δ A_LR can respectively reach -35% and -37.5% for √s=500 GeV and √s=1000 GeV via e⁺e^- collision, which can reach the observable level at the ILC. By contrast, the spin correlation δC is smaller. The correlation behaviors of these observables at the e⁺e^- collision and the γγ collision will be helpful to distinguish different models and test the LHT model at the ILC.
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  Temperature of Heavy Fragments in Heavy-Ion Collisions

  马春旺, 王闪闪, 普洁, 陈丽, 杨杰, 杨佳斌, 郭美婷

  理论物理通讯. 2013, 59(01): 95-98.

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  The heavy fragments in heavy-ion collisions are finally formed after the hot prefragments undergo sequential decay, of whom the temperature should be much lower than that of prefragments. Using the double ratio (DR) method, the isotopic thermometer (T_iso) for heavy fragment is constructed using the yield of heavy isotopes. T_iso of heavy fragment is obtained by analyzing the measured data in the 1A GeV^124,136Xe and 140A MeV⁴⁸Ca/⁶⁴Ni reactions. Result shows that T_iso varies from 0.5 MeV to 10 MeV. But most T_iso is around 1?0.5 MeV, which is much lower than temperature of light particles. Result also indicates that the difference between T_iso of heavy fragments in different reactions is very small, and T_iso is independent on the size of the reaction system, the incident energy and the neutron-richness of the projectile.
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  Stokes' First Problem for an MHD Burgers Fluid

  Masood Khan

  理论物理通讯. 2013, 59(01): 99-104.

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  This work is related to the flow of a magnetohydrodynamic Burgers fluid. The flow of an incompressible conducting Burgers fluid in the presence of a uniform transverse magnetic field over a plate that is moved suddenly is considered. By the application of the Laplace and Fourier sine transforms techniques, the exact analytical expressions for the velocity field and associated shear stress are determined in simple forms. They are written as a sum of steady-state and transient solutions. The graphical results are plotted for different values of indispensable parameters and some interesting results are concluded. The corresponding solutions for the hydrodynamic Burgers fluid appear as the limiting cases of the obtained solutions.
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  First-Principles Calculations on Electronic, Chemical Bonding and Optical Properties of Cubic Hf₃N₄

  冯丽萍, 汪志强, 刘正堂

  理论物理通讯. 2013, 59(01): 105-109.

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  Electronic, chemical bonding and optical properties of cubic Hf₃N₄(c-Hf₃N₄) are calculated using the first-principles based on the density functional theory (DFT). The optimized lattice parameter is in good agreement with the available experimental and calculational values. Band structure shows that c-Hf₃N₄ has direct band gap. Densities of states (DOS) and charge densities indicate that the bonding between Hf and N is ionic. The optical properties including complex dielectric function, refractive index, extinction coefficient, absorption coefficient, and reflectivity are predicted. From the theory of crystal-field and molecular-orbital bonding, the optical transitions of c-Hf₃N₄ affected by the electronic structure and molecular orbital are studied. It is found that the absorptive transitions of c-Hf₃N₄ compound are predominantly composed of the transitions from N T₂2p valence bands to Hf T₂ (d_xy, d_xz, d_yz) conduction bands.
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  Stückelberg Holographic Superconductor Models with Backreactions

  彭严, 潘启沅

  理论物理通讯. 2013, 59(01): 110-116.

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  We study the Stückelberg holographic superconductors away from the probe limit. We find that the backreaction of the spacetime can bring richer physics in the phase transition. Moreover we observe that the ratio ω_g/T_c changes with the strength of the backreaction and is not a universal constant.
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  Electrocaloric Effect of P(VDF-TrFE)/SrTiO₃ Bilayer Thin Films

  邱建华, 丁建宁, 袁宁一, 王秀琴

  理论物理通讯. 2013, 59(01): 117-120.

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  A phenomenological thermodynamic theory is applied to investigate the effect of misfit strain and electric field on the electrocaloric effect of P(VDF-TrFE)/SrTiO₃ bilayer thin films. Theoretical results indicate that the low electric field results in the decrease of the average polarization with the increase of the relative thickness of SrTiO₃ layer, and the high electric field has an opposite effect on it. Moreover, the electrocaloric effect strongly depends on the electric field. The low electric field and the small field change can lead to a maximum of the electrocaloric effect, meanwhile the high electric field or the large field change results in the opposite trend.
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  Simulation Study of the Electron and Hole Transport in a CNTFET

  A. Bahari, M. Amiri

  理论物理通讯. 2013, 59(01): 121-124.

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  In this work we have investigated electron and hole transport through zig zag carbon nanotubes by solving Boltzmann Transport Equation (BTE). We find that the mobility of electrons is rather greater than holes. Carbo nanotubes with longer diameter can carry higher current. Normally, transport of electrons (or holes) is dominated by scattering events, which relax the carrier momentum in an effort to bring the conducting material to equilibrium.
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  Exact Solutions of the Equilibrium Shape Equations in a General WLC Model for DNA Forms

  Morteza Yavari

  理论物理通讯. 2013, 59(01): 125-130.

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  In this letter, we are going to use a geometrical approach to describe the free energy of DNA structures. The exact solutions of the equilibrium shape equations in a general WLC model for DNA forms by using the Feoli's formalism [A. Feoli, et al., Nucl. Phys. B 705 (2005) 577] are studied. Then, the free energy of transition between B- and Z-DNA is calculated in this formalism.