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Dynamical decoupling pulses on the quantum correlations for the system of superconducting quantum circuit

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Chinese physics B 2015年第11期24卷 98-102页

作者：王冬梅钱懿许晶波俞攸红 Zhejiang institute of Modern physics and physics department Zhejiang University Applied physics department Zhejiang University of Technology

We investigate the influence of the dynamical decoupling pulses on the quantum correlations in a superconducting system consisting of two noninteracting qubits interacting with their own data buses. It is found that the geometric discord and entanglement between the two superconducting qubits can be increased by applying a train of zc-phase pulses. We then proceed to explore how the decoupling pulses affect the quantum transfer of information between the two superconducting qubits by makin~ use of the chance of trace distance.

关键词： quantum correlations superconducting qubits decoupling

Chaos and quantum Fisher information in the quantum kicked top

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Chinese physics B 2011年第5期20卷 199-203页

作者：王晓茜马健张喜和王晓光 department of physics Changchun University of Science and Technology Zhejiang institute of Modern physics Department of PhysicsZhejiang University

Quantum Fisher information is related to the problem of parameter estimation. Recently, a criterion has been proposed for entanglement in multipartite systems based on quantum Fisher information. This paper studies the behaviours of quantum Fisher information in the quantum kicked top model, whose classical correspondence can be chaotic. It finds that, first, detected by quantum Fisher information, the quantum kicked top is entangled whether the system is in chaotic or in regular case. Secondly, the quantum Fisher information is larger in chaotic case than that in regular case, which means, the system is more sensitive in the chaotic case.

关键词： quantum information quantum kicked top quantum Fisher information quantum chaos

Improvement of the axial trapping effect using azimuthally polarised trapping beam

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Chinese physics B 2010年第11期19卷 698-703页

作者：李雪璁孙秀冬 department of physics Harbin Institute of Technology

A dual optical tweezers system, which consists of a doughnut mode optical tweezer （DMOT） with the azimuthally polarised trapping beam and a solid mode optical tweezer （SMOT） with the Gauss trapping beam was constructed to compare the axial trapping effect of DMOT and SMOT. The long-distance axial trapping of ST68 microbubbles （MBs） achieved by DMOT was more stable than that of SMOT. Moreover the axial trapping force measured using the viscous drag method, was depended on the diameter of the particle, the laser power, and the numerical aperture （NA） of the objective lens. The measurement of the axial trapping force and the acquisition of CCD images of trapping effect confirmed that the DMOT showed excellent axial trapping ability than SMOT. A simple and effective method is developed to improve axial trapping effect using the azimuthally polarized beam as trapping beam. This is helpful for the long-distance manipulating of particles especially polarised biological objects in axial direction.

关键词： optical tweezers azimuthally polarised beam axial trapping force ST68 microbubbles

Photochemical kinetics for holographic grating formation in phenanthrenequinone doped poly (methyl methacrylate) photopolymer

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Chinese physics B 2009年第10期18卷 4326-4332页

作者：王健孙秀冬骆素华姜永远孟庆鑫 department of physics Harbin Institute of Technology

The photochemical kinetics of phenanthrenequinone （PQ） doped poly （methyl methacrylate） photopolymer in holographic recording was studied theoretically and experimentally. The diffusion of PQ molecules during holographic recording was negligible because of its small diffusion coefficient at room temperature. A photochemical reaction kinetics model of PQ/PMMA was established. The analytical expressions for the temporal variations of transmittance and diffraction efficiency were derived. By fitting the experimental curves, some parameters related with the polymer components were obtained by the proposed model, which can be used to analyze the photochemical process and will be helpful to the optimization of material preparation.

关键词： phenanthrenequinone doped poly(methyl methacrylate) photochemical reaction

Non-equilibrium statistical theory about microscopic fatigue cracks of metal in magnetic field

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Chinese physics B 2010年第10期19卷 597-602页

作者：刘兆龙胡海云范天佑邢修三 department of physics Beijing Institute of Technology

This paper develops the non-equilibrium statistical fatigue damage theory to study the statistical behaviour of micro-crack for metals in magnetic field. The one-dimensional homogeneous crack system is chosen for study. To investigate the effect caused by magnetic field on the statistical distribution of micro-crack in the system, the theoretical analysis on microcrack evolution equation, the average length of micro-crack, density distribution function of microcrack and fatigue fracture probability have been performed. The derived results relate the changes of some quantities, such as average length, density distribution function and fatigue fracture probability, to the applied magnetic field, the magnetic and mechanical properties of metals. It gives a theoretical explanation on the change of fatigue damage due to magnetic fields observed by experiments, and presents an analytic approach on studying the fatigue damage of metal in magnetic field.

关键词： fatigue damage micro-crack distribution non-equilibrium statistical theory magneticfield

Second-harmonic generation circular dichroism spectroscopy from tripod-like chiral molecular films

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Chinese physics B 2010年第11期19卷 427-435页

作者：王晓鸥陈立安陈历学孙秀冬李俊庆李淳飞 department of physics Harbin Institute of Technology

The second-harmonic generation （SHG） circular dichroism in the light of reflection from chiral films of tripod-like chiral molecules is investigated. The expressions of the second-harmonic generation circular dichroism are derived from our presented three-coupled-oscillator model for the tripod-like chiral molecules. Spectral dependence of the circular dichroism of SHG from film surface composed of tripod-like chiral molecules is simulated numerically and analysed. Influence of ehiral parameters on the second-harmonic generation circular dichroism spectrum in chiral films is studied. The result shows that the second-harmonic generation circular dichroism is a sensitive method of detecting chirality compared with the ordinary circular dichroism in linear optics. All of our work indicates that the classical molecular models are very effective to explain the second-harmonic generation circular dichroism of chiral molecular system. The classical molecular model theory can give us a clear physical picture and brings us very instructive information about the link between the molecular configuration and the nonlinear processes.

关键词： circular dichroism three-coupled-oscillator model tripod-like structure second- harmonic generation circular dichroism

Effect of atomic initial phase difference on spontaneous emission of an atom embedded in photonic crystal

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Chinese physics B 2010年第8期19卷 301-306页

作者：张冰孙秀冬姜向前 department of physics Harbin Institute of Technology

We investigate the effect of initial phase difference between the two excited states of a V-type three-level atom on its steady state behaviour of spontaneous emission. A modified density of modes is introduced to calculate the spontaneous emission spectra in photonic crystal. Spectra in free space are also shown to compare with that in photonic crystal with different relative positions of the excited levels from upper band-edge frequency. It is found that the initial phase difference plays an important role in the quantum interference property between the two decay channels. For a zero initial phase, destructive property is presented in the spectra. With the increase of initial phase difference, quantum interference between the two decay channels from upper levels to ground level turns to be constructive. Furthermore, we give an interpretation for the property of these spectra.

关键词： initial phase difference spontaneous emission spectrum quantum interference

A compact frequency selective stop-band splitter by using Fabry Perot nanocavity in a T-shaped waveguide

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Chinese physics B 2013年第4期22卷 513-518页

作者： M Afshari Bavil 孙秀冬 department of physics Harbin Institute of Technology

By utilizing a Fabry–Perot （FP） nanocavity adjacent to T-shaped gap waveguide ports, spectrally selective filtering is realized. When the wavelength of incident light corresponds to the resonance wavelength of the FP nanocavity, the surface plasmons are captured inside the nanocavity, and light is highly reflected from this port. The resonance wavelength is determined by using Fabry–Perot resonance condition for the nanocavity. For any desired filtering frequency the dimension of the nanocavity can be tailored. The numerical results are based on the two-dimensional finite difference time domain simulation under a perfectly matched layer absorbing boundary condition. The analytical and simulation results indicate that the proposed structure can be utilized for filtering and splitting applications.

关键词： T-shaped splitter Fabry–Perot nanocavity spectrally selective splitting finite difference time domain (FDTD) simulation

Spin-valley quantum Hall phases in graphene

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Chinese physics B 2015年第12期24卷 477-482页

作者：田宏玉 department of physics Yancheng Institute of Technology

We theoretically investigate possible quantum Hall phases and corresponding edge states in graphene by taking a strong magnetic field, Zeeman splitting M, and sublattice potential △ into account but without spin–orbit interaction. It was found that for the undoped graphene either a quantum valley Hall phase or a quantum spin Hall phase emerges in the system, depending on relative magnitudes of M and △. When the Fermi energy deviates from the Dirac point, the quantum spin-valley Hall phase appears and its characteristic edge state is contributed only by one spin and one valley species. The metallic boundary states bridging different quantum Hall phases possess a half-integer quantized conductance, like e^2/2h or3e^2/2h. The possibility of tuning different quantum Hall states with M and △ suggests possible graphene-based spintronics and valleytronics applications.

关键词： quantum Hall phases graphene magnetic field metallic boundary states