2014年, 第62卷, 第02期　
刊出日期：2014-08-01

  

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  A New Fractional Projective Riccati Equation Method for Solving Fractional Partial Differential Equations

  冯青华

  理论物理通讯. 2014, 62(02): 167-172.

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  In this paper, a new fractional projective Riccati equation method is proposed to establish exact solutions for fractional partial differential equations in the sense of modified Riemann—Liouville derivative. This method can be seen as the fractional version of the known projective Riccati equation method. For illustrating the validity of this method, we apply this method to solve the space—time fractional Whitham—Broer—Kaup (WBK) equations and the nonlinear fractional Sharma—Tasso—Olever (STO) equation, and as a result, some new exact solutions for them are obtained.
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  Symmetry Analysis and Conservation Laws to the (2+1)-Dimensional Coupled Nonlinear Extension of the Reaction-Diffusion Equation

  陈俊超, 辛祥鹏, 陈勇

  理论物理通讯. 2014, 62(02): 173-182.

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  In this paper, a detailed Lie symmetry analysis of the (2+1)-dimensional coupled nonlinear extension of the reaction-diffusion equation is presented. The general finite transformation group is derived via a simple direct method, which is equivalent to Lie point symmetry group actually. Similarity reduction and some exact solutions of the original equation are obtained based on the optimal system of one-dimensional subalgebras. In addition, conservation laws are constructed by employing the new conservation theorem.
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  Influence of Composite Effect from Quantum Channels on Entanglement

  胡菊菊, 李帅

  理论物理通讯. 2014, 62(02): 183-188.

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  The dynamics of entanglement between two qubits in the local damping two-sided channel and single-sided channel are compared through non-Markovian process and Markovian process. The entanglement between two qubits is found to be longer in the single-sided channel case due to the weakening of the dissipative effects. In the two-sided channel, influenced by the entanglement between qubits, the previous independent dissipative channels incline to the composite effect of the Markovian process. This composite effect results in the dissipative effect of one channel affecting the qubits in the other channel, especially inhibiting the backflow effect in the non-Markovian channel, which is disadvantageous to the entanglement maintenance between qubits. In the Markovian channel, the composite effect of the damping two-sided channels is more obvious since there is no backflow effect, thus more disadvantageous to the entanglement maintenance.
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  One Electron Atom in Special Relativity with de Sitter Space-Time Symmetry (II)：—Higher Order Contributions

  闫沐霖

  理论物理通讯. 2014, 62(02): 189-195.

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  This is a follow of previous work entitled "One Electron Atom in Special Relativity with de Sitter Space-Time Symmetry" [Commun. Theor. Phys. 57 (2012) 930]. In this paper, we consider the higher order calculations and contributions in the previous framework to solve one electron atoms in de Sitter invariant relativistic quantum mechanics. The next-to-leading-order calculations in 1/R²-expansions show that the fine-structure constant α is variant with cosmologic time going by in the de Sitter invariant special relativistic quantum mechanics with standard FRW cosmologic model.
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  Spin Ensembles Coupled to Superconducting Resonators：A Scalable Architecture for Solid-State Quantum Computing

  陈昌永, 侯其哲, 李韶华

  理论物理通讯. 2014, 62(02): 196-204.

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  A design is proposed for scalable solid-state quantum computing, which is based on collectively enhanced magnetic coupling between nitrogen-vacancy center ensembles and superconducting transmission line resonators interconnected by current-biased Josephson junction superconducting phase qubit. In this hybrid system, we realize distant multi-qubit controlled phase gate operations and generate distant multi-qubit entangled W-like states, being indispensable resource to quantum computation. Our proposed architecture consists of solid-state spin ensembles and circuit QED, and could achieve quantum computing in a solid-state environment with high-fidelity and scalable way. The experimental feasibility is discussed, and the implementation efficiency is demonstrated numerically.
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  Separability of Solutions to a Schrödinger Equation

  王文华, 曹怀信, 郭志华, 余保民

  理论物理通讯. 2014, 62(02): 205-209.

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  We discuss separability of solutions to a Schrödinger equation that describes a composite quantum system and give some kinds of Hamiltonians H(t) such that the solution to Schrödinger equation induced by H(t) is separable at any time provided that it is separable at t=0. For example, we prove that if the Hamiltonian H is time-independent and equals to the product P_A  P_B of two projections on the subsystems K_A and K_B , respectively, then the state |ψ(t)> of the composite system starting from a separable initial |ψ(0)>=|ψA>|ψB> is separable for all t∈ [0,T] if and only if either |ψA> is an eigenstate of P_A, or |ψB> is an eigenstate of P_B.
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  Cryptanalysis and Improvement of Quantum Private Comparison Protocol Based on Bell Entangled States

  刘文杰, 刘超, 陈汉武, 李志强, 刘志昊

  理论物理通讯. 2014, 62(02): 210-214.

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  Recently, Liu et al. [Commun. Theor. Phys. 57 (2012) 583] proposed a quantum private comparison protocol based on entanglement swapping of Bell states, which aims to securely compare the equality of two participants' information with the help of a semi-honest third party (TP). However, the present study points out there is a fatal loophole in Liu et al.'s protocol, and TP can make Bell-basis measurement to know all the participants' secret inputs without being detected. To fix the problem, a simple solution, which uses one-time eavesdropper checking with decoy photons instead of twice eavesdropper checking with Bell states, is demonstrated. Compared with the original protocol, it not only reduces the Bell states consumption but also simplifies the protocol steps.
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  Splitting Single-Photon Polarization State with Weak Cross—Kerr Nonlinearity

  芮品淑, 熊狂炜, 章文, 张子云

  理论物理通讯. 2014, 62(02): 215-220.

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  We propose a three-party scheme for quantum information splitting (QIS) of an arbitrary single-photon polarization state based on weak cross-Kerr nonlinearity combined with linear optics elements such as polarization beam splitters (PBSs) and half wave plates (HWPs). The scheme is generalized to the arbitrary-party case. With the help of quantum nondemolition (QND) measurements, our schemes can be accomplished in an almost deterministic way. The two schemes are feasible with the current technology.
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  Exact Solution of a (2+1)-Dimensional Anisotropic Star in Finch and Skea Spacetime

  Piyali Bhar, Farook Rahaman, Ritabrata Biswas, Hafiza Ismat Fatima

  理论物理通讯. 2014, 62(02): 221-226.

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  We provide a new class of interior solution of a (2+1)-dimensional anisotropic star in Finch and Skea spacetime corresponding to the BTZ black hole. We develop the model by considering the MIT bag model EOS and a particular ansatz for the metric function g_rr proposed by Finch and Skea [M.R. Finch and J.E.F. Skea, Class. Quantum. Grav. 6 (1989) 467]. Our model is free from central singularity and satisfies all the physical requirements for the acceptability of the model.
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  Absorption/Scattering of Massless Dirac Wave from Black Hole Spacetimes with Cosmic String

  廖浩, 陈菊华, 廖平, 王永久

  理论物理通讯. 2014, 62(02): 227-234.

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  In this paper we investigate the scattering of massless Dirac wave from several different black hole spacetimes (i.e. the Schwarzschild black hole, the RN extremal black hole, the Schwarzschild de Sitter black hole, and the extremal Schwarzschild de Sitter black hole) which are influenced by the cosmic string, respectively. All these cases show us that the total absorption cross sections oscillate around the geometric-optical limit and decrease with linear mass density μ of the cosmic string. All of the total scattering cross sections exhibit that the main scattering angle becomes narrower for the high partial frequency wave. Due to the influence of cosmic string, the glory peak becomes wider for larger values of linear mass density μ of the cosmic string.
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  Pfaffian Solutions and Resonant Interaction Properties of a Coupled BKP Lattice

  赵海琼, 虞国富

  理论物理通讯. 2014, 62(02): 235-244.

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  In this paper, we give a coupled lattice equation with the help of Hirota operators, which comes from a special BKP lattice. Two-soliton and three-soliton solutions to the coupled system are constructed. Furthermore, resonant interaction of the two-soliton solution is analyzed in detail. Under some special resonant condition, it is shown that low soliton can propagate faster than high one. Finally, the N-soliton solution is presented in the Pfaffian form.
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  On the Quasi-Periodic Wave Solutions and Asymptotic Analysis to a (3+1)-Dimensional Generalized Kadomtsev—Petviashvili Equation

  田守富, 马潘丽

  理论物理通讯. 2014, 62(02): 245-258.

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  In this paper, a (3+1)-dimensional generalized Kadomtsev—Petviashvili (GKP) equation is investigated, which can be used to describe many nonlinear phenomena in fluid dynamics and plasma physics. Based on the generalized Bell's polynomials, we succinctly construct the Hirota's bilinear equation to the GKP equation. By virtue of multidimensional Riemann theta functions, a lucid and straightforward way is presented to explicitly construct multiperiodic Riemann theta function periodic waves (quasi-periodic waves) for the (3+1)-dimensional GKP equation. Interestingly, the one-periodic waves are well-known cnoidal waves, which are considered as one-dimensional models of periodic waves. The two-periodic waves are a direct generalization of one-periodic waves, their surface pattern is two-dimensional that they have two independent spatial periods in two independent horizontal directions. Finally, we analyze asymptotic behavior of the multiperiodic periodic waves, and rigorously present the relationships between the periodic waves and soliton solutions by a limiting procedure.
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  A Lattice Model for Bidirectional Pedestrian Flow on Gradient Road

  葛洪霞, 程荣军, 卢兆明

  理论物理通讯. 2014, 62(02): 259-264.

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  Ramps and sloping roads appear everywhere in the built environment. It is obvious that the movement pattern of people in the sloping path may be different as compared with the pattern on level roads. Previously, most of the studies, especially the mathematical and simulation models, on pedestrian movement consider the flow at level routes. This study proposes a new lattice model for bidirectional pedestrian flow on gradient road. The stability condition is obtained by using linear stability theory. The nonlinear analysis method is employed to derive the modified Korteweg-de Vries (mKdV) equation, and the space of pedestrian flow is divided into three regions: the stable region, the metastable region, and the unstable region respectively. Furthermore, the time-dependent Ginzburg—Landan (TDGL) equation is deduced and solved through the reductive perturbation method. Finally, we present detailed results obtained from the model, and it is found that the stability of the model is enhanced in uphill situation while reduced in downhill situation with increasing slope.
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  A Note on Black Holes in Asymptotically Lifshitz Spacetime

  庞大伟

  理论物理通讯. 2014, 62(02): 265-271.

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  We investigate several aspects of exact black hole solutions in asymptotically Lifshitz spacetime. Firstly, we calculate the tidal forces and find that in the near horizon region of such black hole backgrounds, the tidal forces diverge in the near extremal limit. Secondly, we evaluate the Wilson loops in both extremal and finite temperature cases. Finally, we obtain the corresponding shear viscosity and square of the sound speed and find that the ratio of shear viscosity to entropy density takes the universal value 1/4π in arbitrary dimensions while the square of the speed of sound saturates the conjectured bound 1/3 in five dimensions.
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  Effects of Parametrization of A Woods—Saxon Potential on Single Particle Orbits in ⁶⁶Ca

  吕洪凤, 王小素, 刘玉颖

  理论物理通讯. 2014, 62(02): 272-276.

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  A Woods—Saxon potential is introduced to serve as initial conditions for an iterative solution of the exotic nuclei in relativistic mean field approach. Effects of parametrization of the Woods—Saxon potential on single particle orbits around the Fermi surface are investigated in ⁶⁶Ca. A semi-parabolic curve of orbital radius appears when the width of the central potential changes. The pseduospin splitting is more sensitive to the potential width than to the depth and the diffuseness. The spin-orbit splitting is more sensitive to the potential depth than to the width and the diffuseness.
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  Coherent Single-Electron Transfer in Coupled Semiconductor Quantum Dots Driven by a Few-Cycle Pulse

  杨文星, 陈爱喜, 白艳锋, 陆加伟

  理论物理通讯. 2014, 62(02): 277-282.

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  We theoretically study the coherent transport of a single electron between the ground states of a double coupled quantum dot structure. The coherent transport is externally controlled by applying a few-cycle pulse with an adjustable carrier-envelope phase (CEP). By simulating numerically, it is shown that there exhibits a strong dependence of electron transport on the CEP and on the arrival time of few-cycle pulse. We provide a simple analytical description for this phenomenon by approximating the quantum dot structure as a three-level Λ-type system. These results also illustrate the potential of utilizing excitation in coupled quantum dots as a means of measuring the CEP of few-cycle pulses.
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  Electronic and Optical Properties of a Lens Shaped Quantum Dot under Magnetic Field：Second and Third-Harmonic Generation

  R. Khordad, H. Bahramiyan

  理论物理通讯. 2014, 62(02): 283-289.

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  In the present work, we have studied electronic and optical properties of a lens-shaped quantum dot under an external magnetic field. For this goal, we have calculated the energy levels and wave functions using the finite element method (FEM) for different values of magnetic field. We have also studied effect of magnetic field on second harmonic generation (SHG) and third-harmonic generation (THG) in the lens-shaped quantum dot. In this regard, we have obtained an analytic expression for the SHG and THG by a compact density matrix approach and an iterative procedure. According to the obtained results, it is found that the presence of the magnetic field affects the symmetry of the system. The SHG and THG are decreased with increasing the magnetic field. The magnetic field has a great influence on the energy levels, wave functions, the SHG and THG in a lens shaped quantum dot.
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  Extension of Compressibility-Route Cubic Equations of State and the Radial Distribution Functions at Contact to Multi-Component Hard-Sphere Mixtures

  孙久勋, 金柯, 蔡灵仓, 吴强

  理论物理通讯. 2014, 62(02): 290-296.

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  The equation of state (EOS) for hard-sphere fluid derived from compressibility routes of Percus-Yevick theory (PYC) is extended. The two parameters are determined by fitting well-known virial coefficients of pure fluid. The extended cubic EOS can be directly extended to multi-component mixtures, merely demanding the EOS of mixtures also is cubic and combining two physical conditions for the radial distribution functions at contact (RDFC) of mixtures. The calculated virial coefficients of pure fluid and predicted compressibility factors and RDFC for both pure fluid and mixtures are excellent as compared with the simulation data. The values of RDFC for mixtures with extremely large size ratio 10 are far better than the BGHLL expressions in literature.