2017年, 第67卷, 第04期　
刊出日期：2017-04-01

  

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  Equal-Time and Equal-Space Poisson Brackets of the N-Component Coupled NLS Equation

  周汝光, 李佩瑶, 高媛

  理论物理通讯. 2017, 67(04): 347-349.

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  Two Poisson brackets for the N-component coupled nonlinear Schrödinger (NLS) equation are derived by using the variantional principle. The first one is called the equal-time Poisson bracket which does not depend on time but only on the space variable. Actually it is just the usual one describing the time evolution of system in the traditional theory of integrable Hamiltonian systems. The second one is equal-space and new. It is shown that the spatial part of Lax pair with respect to the equal-time Poisson bracket and temporal part of Lax pair with respect to the equal-space Poisson bracket share the same r-matrix formulation. These properties are similar to that of the NLS equation.
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  Accidental Degeneracies in N dimensions for Potential Class αr^2d-2-βr^d-2 via Asymptotic Iteration Method (AIM)

  H. F. Kisoglu, Hakan Ciftci

  理论物理通讯. 2017, 67(04): 350-354.

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  In mathematical physics the main goal of quantum mechanics is to obtain the energy spectrum of an atomic system. In many practices, Schrödinger equation which is a second order and linear differential equation is solved to do this analysis. There are many theoretic mathematical methods serving this purpose. We use Asymptotic Iteration Method (AIM) to obtain the energy eigenvalues of Schrödinger equation in N-dimensional euclidean space for a potential class given as αr^2d-2-βr^d-2. We also obtain a restriction on the eigenvalues that gives degeneracies. Besides, we crosscheck the eigenvalues and degeneracies using the perturbation theory in the view of the AIM.
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  Success Rate Versus Finite Run Time in Local Adiabatic Quantum Search Algorithm

  李风光, 鲍皖苏, 汪翔, 付向群, 张硕, 杜宇韬, 李坦, 马博文

  理论物理通讯. 2017, 67(04): 355-359.

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  In adiabatic quantum algorithm, the success rate is approximately equal to 1 while the run time satisfies the adiabatic condition. But the relation between the short run time and success rate for adiabatic quantum algorithm is poorly understood. In this paper, we study the success rate of local adiabatic quantum search algorithm with an arbitrary finite run time (non-adiabatic evolution). By solving the time-independent Schrödinger equation, we obtain differential equations to calculate the success rate. The differential equations show that the success rate is closely related to the adiabatic parameter s(t). Utilize the differential equations, we give the function of success rate versus run time in local adiabatic search numerically. The result indirectly verifies that T~O(√N) is optimal in local adiabatic search.
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  Error Rate Estimation in Quantum Key Distribution with Finite Resources

  卢钊, 史建红, 李风光

  理论物理通讯. 2017, 67(04): 360-364.

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  The goal of quantum key distribution (QKD) is to generate secret key shared between two distant players, Alice and Bob. We present the connection between sampling rate and erroneous judgment probability when estimating error rate with random sampling method, and propose a method to compute optimal sampling rate, which can maximize final secure key generation rate. These results can be applied to choose the optimal sampling rate and improve the performance of QKD system with finite resources.
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  Dynamics of Nonclassicality of Time- and Conductivity-Dependent Squeezed States and Excited Even/Odd Coherent States

  R. Daneshmand, M. K. Tavassoly

  理论物理通讯. 2017, 67(04): 365-376.

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  Recently, the quantum description of electromagnetic waves in conducting media has been performed. It has been demonstrated that in particular case, the Hamiltonian of the corresponding field can be expressed by Caldirola-Kanai Hamiltonian. In this paper, using the associated annihilation and creation operators of the above-mentioned quantized field, the time- and conductivity-dependent squeezed vacuum and one-photon squeezed states as well as their superpositions, and also the time- and conductivity-dependent excited even and odd coherent states are produced. Also, using a few well-known nonclassicality criteria, the time evolution of nonclassicality features of the above classes of obtained states, in addition to the influence of medium conductivity on them are demonstrated, numerically. It has been shown that the nonclassicality indicators may be adjusted by tuning the conductivity of media.
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  Probabilistic Teleportation of an Arbitrary Two-Qubit State via Positive Operator-Valued Measurement with Multi Parties

  石磊, 魏家华, 李云霞, 马丽华, 薛阳, 罗均文

  理论物理通讯. 2017, 67(04): 377-382.

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  We propose a novel scheme to probabilistically transmit an arbitrary unknown two-qubit quantum state via Positive Operator-Valued Measurement with the help of two partially entangled states. In this scheme, the teleportation with two senders and two receives can be realized when the information of non-maximally entangled states is only available for the senders. Furthermore, the concrete implementation processes of this proposal are presented, meanwhile the classical communication cost and the successful probability of our scheme are calculated.
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  Prefect Protection of Quantum-Enhanced Metrology from Dephasing Noise

  钟伟, 黄奕筱, 王晓光

  理论物理通讯. 2017, 67(04): 383-390.

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  One of the main obstacles for quantum-enhanced metrology is that the estimation accuracy enhanced by non-classical states is likely to be obliterated by noises. Here, we consider a scenario of phase estimation suffering from pure dephasing noise which is taken into account after the phase parameter being imprinted, and propose a scheme to effectively protect the quantum enhancement from both correlated and uncorrelated dephasing sources by performing a rotation operation prior to the noise. By invoking the Fisher information approach, we strictly prove that a π/2 rotation is the ideal one which can completely resist the influence of the phase noise for all real symmetric pure states and the optimal measurement approaching the ultimate sensitivity set by quantum Cramér-Rao bound is presented. Additionally, we numerically study the availability of the scheme with arbitrary angle rotation for different probe states and show that our scheme will still robust for general symmetric pure states even with non-ideal rotation operation.
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  A Simple Method on Generating any Bi-Photon Superposition State with Linear Optics

  张婷婷, 魏杰, 王琴

  理论物理通讯. 2017, 67(04): 391-395.

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  We present a simple method on the generation of any bi-photon superposition state using only linear optics. In this scheme, the input states, a two-mode squeezed state and a bi-photon state, meet on a beam-splitter and the output states are post-selected with two threshold single-photon detectors. We carry out corresponding numerical simulations by accounting for practical experimental conditions, calculating both the Wigner function and the state fidelity of those generated bi-photon superposition states. Our simulation results demonstrate that not only distinct nonclassical characteristics but also very high state fidelities can be achieved even under imperfect experimental conditions.
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  A Few Discrete Lattice Systems and Their Hamiltonian Structures, Conservation Laws

  郭秀荣, 张玉峰, 张祥芝, 岳嵘

  理论物理通讯. 2017, 67(04): 396-406.

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  With the help of three shift operators and r-matrix theory, a few discrete lattice systems are obtained which can be reduced to the well-known Toda lattice equation with a constraint whose Hamiltonian structures are generated by Poisson tensors of some induced Lie-Poisson bracket. The recursion operators of these lattice systems are constructed starting from Lax representations. Finally, reducing the given shift operators to get a simpler one and its expanding shift operators, we produce a lattice system with three vector fields whose recursion operator is given. Furthermore, we reduce the lattice system with three vector fields to get a lattice system whose Lax pair and conservation laws are obtained, respectively.
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  Braneworld Black Hole Gravitational Lensing

  梁钧

  理论物理通讯. 2017, 67(04): 407-414.

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  A class of braneworld black holes, which I called as Bronnikov-Melnikov-Dehen (BMD) black holes, are studied as gravitational lenses. I obtain the deflection angle in the strong deflection limit, and further calculate the angular positions and magnifications of relativistic images as well as the time delay between different relativistic images. I also compare the results with those obtained for Schwarzschild and two braneworld black holes, i.e., the tidal Reissner-Nordström (R-N) and the Casadio-Fabbri-Mazzacurati (CFM) black holes.
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  Higgs and Single Top Associated Production at the LHC in the Left-Right Twin Higgs Model

  蒋兴雨, 韩金钟, 杨光, 喻纯旭

  理论物理通讯. 2017, 67(04): 415-420.

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  In the framework of the left-right twin Higgs (LRTH) model, we study the Higgs boson and single top quark associated production at the LHC. We investigate the processes pp→thj, pp→thb and pp→thW at the 8(14) TeV LHC and find that the production cross sections of the three processes can be enhanced at different levels. Among them, the production cross section of the process pp→thb is enhanced significantly due to the contribution of the new particles predicted by the LRTH model.
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  Quantum Phases of Cold Bosonic Atoms in an Optical Lattice with Inhomogeneous Atomic Interactions and Coexistence of Multi Phases

  李艳英, 侯净敏

  理论物理通讯. 2017, 67(04): 421-424.

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  We study cold bosonic atoms on a two-dimensional inhomogeneous optical lattice with site-dependent atomic interactions. With the tight-binding approximation, we derive the extended Bose-Hubbard model. Base on the mean-field approximation, the ground states are solved by the exact diagonalization method. We calculate the mean-field order parameter and particle number density for the ground states. We find the coexistence of superfluid phase and Mott-insulator phase on the two-dimensional inhomogeneous optical lattice in appropriate parameter ranges.
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  Special Property of Group Velocity for Temporal Dark Soliton

  杜英杰, 于金影, 白晋涛

  理论物理通讯. 2017, 67(04): 425-429.

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  We investigate the speed of temporal dark soliton based on an optical coherent medium. It is demonstrated that the temporal dark soliton is described by a nonlinear Schrodinger equation whose coefficients are decided by the coherent medium. It is found that the speed of temporal dark soliton not only relies on the linear responses including GV parameter, group velocity dispersion parameter as well as the amplitude of dark soliton, but also relies on the nonlinear response like self-phase modulation parameter. Additionally, the dark soliton in anomalous-dispersion regime propagates slower than bright soliton, while in normal-dispersion regime it inversely propagates faster than bright soliton. The complicated property of the speed for dark soliton is quite different from the bright soliton whose speed is commonly only related to the group velocity parameter. We attribute this feature to the modulation instability of the nonlinear system.
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  Collisions and Trapping of Time Delayed Solitons in Optical Waveguides with Orthogonally Polarized Modes

  周欢, 李金花, 周国荣, 肖韶荣, 孙婷婷

  理论物理通讯. 2017, 67(04): 430-434.

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  The interactions and collisions of time delayed solitons in optical waveguides with orthogonally polarized modes are studied. Direct numerical simulations of the coherently coupled nonlinear Schrödinger equations are performed, and neither the high birefringence nor the low birefringence approximations are invoked. Trapping of solitary pulses occurs when the birefringence parameter is small or the four-wave mixing parameter is large. The distance before the first collision depends strongly on the initial separation of the two solitary pulses. Variational techniques are employed to calculate this distance, and results agree with those from the full simulations very well.
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  Dynamics of Optical Bistability with Kerr-nonlinear Blackbody Radiation Reservoir

  Yasser A. Sharaby

  理论物理通讯. 2017, 67(04): 435-442.

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  In this paper we investigate the nonlinear dynamics for optical bistabile (OB) model of homogeneously broadened two-level atomic medium interacting with a single mode of the ring cavity in the presence of a Kerr-nonlinear blackbody (KNB) radiation reservoir. We show the impact of the relative temperature of the reservoir on the transition between the dynamical states via bifurcation diagrams that represents the relation between maximum values of the output field and the relative temperature for fixed input field. Specifically, decreasing the relative temperature (T_b) causes the system to bifurcate from periodic to chaotic behavior and in turn reverts back to periodic behavior with further decrease of T_b. Varying atomic detuning leads to a change in the nature of the dynamic transition between the system's states from self pulsing to chaotic behavior.
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  Numerical Investigation of Micropolar Casson Fluid over a Stretching Sheet with Internal Heating

  Zaffar Mehmood, R. Mehmood, Z. Iqbal

  理论物理通讯. 2017, 67(04): 443-448.

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  This theoretical study investigates the microrotation effects on mixed convection flow induced by a stretching sheet. Casson fluid model along with microrotation is considered to model the governing flow problem. The system is assumed to undergo internal heating phenomenon. The governing physical problem is transformed into system of nonlinear ordinary differential equations using scaling group of transformations. These equations are solved numerically using Runge Kutta Fehlberg scheme coupled with shooting technique. Influence of sundry parameters for the case of strong and weak concentration of microelements on velocity, temperature, skin friction and local heat flux at the surface are computed and discussed. Lower skin friction and heat flux is observed for the case of weak concentration (n=0.5) compared to strong concentration of microelements (n=0.0) near the wall.
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  Dual Solutions of MHD Boundary Layer Flow of a Micropolar Fluid with Weak Concentration over a Stretching/Shrinking Sheet

  Z. H. Khan, M. Qasim, Naeema Ishfaq, W. A. Khan

  理论物理通讯. 2017, 67(04): 449-457.

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  We investigate the dual solutions for the MHD flow of micropolar fluid over a stretching/shrinking sheet with heat transfer. Suitable relations transform the partial differential equations into the ordinary differential equations. Closed forms solutions are also obtained in terms of confluent hypergeometric function. This is the first attempt to determine the exact solutions for the non-linear equations of MHD micropolar fluid model. It is demonstrated that the microrotation parameter helps in increasing Nusselt number and the dual solutions exist for all fluid flow parameters under consideration. The dual behavior of dimensionless velocity, temperature, microrotation, skin-friction coefficient, local Nusselt number is displayed on graphs and examined.
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  Instability Analysis of Positron-Acoustic Waves in a Magnetized Multi-Species Plasma

  M. A. Hossen, M. G. Shah, M. R. Hossen, A. A. Mamun

  理论物理通讯. 2017, 67(04): 458-466.

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  The nonlinear propagation of electrostatic excitations and their multi-dimensional instability in a magnetized, degenerate electron-positron-ion (EPI) plasma system (containing inertial cold positrons, relativistic degenerate electrons and hot positrons, and negatively charged immobile heavy ions) are theoretically investigated. The reductive perturbation method is employed to derive the Zakharov-Kuznetsov equation which admits a localized solitary wave solution for small but finite amplitude limit, and the multi-dimensional instability of the positron acoustic solitary waves (PASWs) is studied by the small-k perturbation expansion method. It is found that the basic characteristics (viz. phase speed, amplitude, width) of the PASWs are significantly affected by the degree of obliqueness, relativistic degeneracy, and plasma particle number densities. The instability criterion and its growth rate, which are depending on the magnetic field and the propagation directions of both the PASWs, and their perturbation modes are discussed. The present analysis can be helpful in understanding the nonlinear phenomenon in dense astrophysical as well as space plasma systems, especially in pulsar environments.