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Control of Fractal Erosion of Safe Basins in a Holmes-Duffing System via Delayed Position Feedback

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Chinese physics Letters 2011年第1期28卷 36-38页

作者： SHANG Hui-Lin School of Mechanical and Automation Engineering Shanghai Institute of Technology Shanghai 200235

A linear delayed position feedback control is applied to control the erosion of safe basins in a Holmes-Duffing system. The conditions of fractal erosion of the safe basin of the controlled system on the basis that the range of time delay leading to good control is obtained by the Melnikov method. It is found that the increasing time delay can reduce the basin erosion under a weak and positive feedback g^in. Then the evolutions of safe basins with time delay are presented in detail by the fourth Runge-Kutta and Monte-Carlo methods, which shows that the safe basin of the controlled Holmes Dulling system can be expanded, and its fractal can be reduced by the increasing time delay. These results suggest that delayed position feedbacks can be used as a good approach to control the erosion of safe basins.

关键词： computational physics Statistical physics and nonlinear systems

Quantum Phase Transition of the Bosonic Atoms near the Feshbach Resonance in an Optical Lattice

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Chinese physics Letters 2010年第12期27卷 65-68页

作者：李犇陈景标 Institute of Quantum Electronics and State Key Laboratory of Advanced Optical Communication System ~z Network School of Electronics Engineering & Computer Science Peking University Beijing 100871

The quantum phase transition from the Mott insulator to the superfluid phases of the bosonic atoms trapped in an optical lattice, in which the on-site interaction carl be tuned by a Feshbach resonance, is investigated by a variational approach within mean-field theory. We derive an extended Bos^Hubbard model to describe this ultracold atomic system. By theoretical calculation and analysis, the phase diagram is shown clearly, and we find an exciting and novel phenomenon that is the appearance of the Mort insulator-sea （MI-sea）. Meanwhile, the experimental feasibility of observing the MI-sea is discussed by analyzing the published data related to the Fashbaeh resonance at present. Finally, the potential application of the MI-sea for quantum information processing and quantum computation is also discussed in detail

关键词： Atomic and molecular physics Quantum gases, liquids and solids computational physics Statistical physics and nonlinear systems

Bidirectional Mapping between a Biphoton Polarization State and a Single-Photon Two-Qubit State

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Chinese physics Letters 2010年第12期27卷 11-14页

作者：林青 College of Information Science and Engineering Huaqiao University Xiamen 361021

How to manipulate （operate or measure） single photons efficiently and simply is the basic problem in optical quantum information processing. We first present an efficient scheme to transform a biphoton polarization state to a corresponding single-photon state encoded by its polarization and spatial modes. This single-photon state carries both the information of the controlled and target photons. It will make the realization of bipartite positive- operator-valued measurements efficiently and simply. Moreover, the inverse transformation from the single-photon state back to the corresponding biphoton polarization state is also proposed. Using both the transformations, the realization of the arbitrary two-qubit unitary operation is simple with an M-Z interferometer. All the schemes are feasible with the current experimental technology.

关键词： computational physics Optics, quantum optics and lasers Quantum information and quantum mechanics

The Time Division Multi-Channel Communication Model and the Correlative Protocol Based on Quantum Time Division Multi-Channel Communication

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Chinese physics Letters 2010年第12期27卷 15-18页

作者：刘晓慧裴昌幸聂敏 State Key Lab of Integrated Service Networks Xidian University Xi'an 710071 School of Communication and Information Engineering Xi'an Institute of Post and Telecommunication Xi'an 710061

Based on the classical time division multi-channel communication theory, we present a scheme of quantum time- division multi-channel communication （QTDMC）. Moreover, the model of quantum time division switch （QTDS） and correlative protocol of QTDMC are proposed. The quantum bit error rate （QBER） is analyzed and the QBER simulation test is performed. The scheme shows that the QTDS can carry out multi-user communication through quantum channel, the QBER can also reach the reliability requirement of communication, and the protocol of QTDMC has high practicability and transplantable. The scheme of QTDS may play an important role in the establishment of quantum communication in a large scale in the future.

关键词： computational physics Electronics and devices Quantum information and quantum mechanics

A Simple Birefringent Terahertz Waveguide Based on Polymer Elliptical Tube

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Chinese physics Letters 2011年第1期28卷 112-114页

作者： WANG Jing-Li YAO Jian-Quan CHEN He-Ming LI Zhong-Yang Institute of Laser and Optoelectronics Key Laboratory of Optoelectronic Information Science and Technology (Ministry of Education) College of Precision Instrument and Optoelectronic Engineering Tianjin University Tianjin 300072 College of Optoelectronic Engineering Institute of Optical Communications Nanjing University of Posts and Telecommunications Nanjing 210003

We propose a simple birefringent terahertz （THz） waveguide which is a polymer elliptical tube with a cross section of elliptical ring structure. It can be achieved by stretching a normal circular-tube in one direction. Simulations based on the full-vector finite element method （FEM） show that this kind of waveguides exhibits high birefringenee on a level of 10- 2 over a wide THz frequency range. Moreover, as a majority of modal power is trapped in the air core inside the polymer elliptical tube, the THz waveguide guiding loss caused by material absorption can be reduced effectively.

关键词： computational physics Electronics and devices

Efficient and Robust Design for Absorbing Boundary Conditions in Atomistic Computations

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Chinese physics Letters 2009年第11期26卷 148-151页

作者：方明唐少强 Center for Applied physics and Technology and LTCS Department of Mechanics and Aerospace Engineering College of Engineering Peking University Beijing 100871

We propose an efficient and robust way to design absorbing boundary conditions in atomistic computations. An optimal discrete boundary condition is obtained by minimizing a functional of a reflection coefficient integral over a range of wave numbers. The minimization is performed with respect to a set of wave numbers, at which transparent absorption is reached. Compared with the optimization with respect to the boundary condition coefficients suggested by E and Huang [Phys. Rev. Lett. 87 （2001） 133501], we reduce considerably the number of independent variables and the computing cost. We further demonstrate with numerical examples that both the optimization and the wave absorption are more robust in the proposed design.

关键词： computational physics

Maximal Violation of Bell Inequality for Any Given Two-Qubit Pure State

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Chinese physics Letters 2010年第12期27卷 8-10页

作者：向阳 School of physics and Electronics Henan University Kaifeng 475004

In the case of bipartite two-qubit systems, we derive an analytical expression of bound Bell operator for any given pure state. Our result not only manifests some properties of Bell inequality, for example, which may be violated by any pure entangled state and only be maximally violated for a maximally entangled state, but also gives the explicit values of maximal violation for any pure state. Finally we point out that any mixed states which can produce maximal violation of Bell inequality must have a maximal concurrence value.

关键词： Mathematical physics computational physics Quantum information and quantum mechanics

Homotopy Analysis Approach to Periodic Solutions of a Nonlinear Jerk Equation

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Chinese physics Letters 2009年第12期26卷 160-163页

作者：冯少东陈立群 Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 Department of Mechanics Shanghai University Shanghai 200444

The homotopy analysis method is applied to seek periodic solutions of a nonlinear jerk equation involving the third-order time-derivative. The periodic solutions can be approximated via an analytical series. An auxiliary parameter is introduced to control the convergence region of the solution series. Two numerical examples are presented to demonstrate the effectiveness of the homotopy analysis approach. The examples indicate that, by choosing a proper value of the auxiliary parameter, the first few terms in the solution series yield excellent results.

关键词： computational physics

Monte Carlo Hamiltonian： Inverse Potential

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Communications in Theoretical physics 2004年第4期41卷 509-512页

作者： LUOXiang-Qian CHENGXiao-Ni HelmutKROeGER Departmentofphysics ZhongshanUniversityGuangzhou510275China DépartementdePhysique UniversitéLavalQuébecQuébecG1K7P4Canada

The Monte Carlo Hamiltonian method developed recently allows to investigate the ground state and low-lying excited states of a quantum system,using Monte Carlo(MC)algorithm with importance ***,conventional MC algorithm has some difficulties when applied to inverse *** propose to use effective potential and extrapolation method to solve the *** present examples from the hydrogen system.

关键词： Monte Carlo method quantum mechanics computational physics