Tunable Nongeometric Phase Gates for Two Hot Ions via Adiabatic Evolution of Dark States

We propose a scheme for implementing nongeometric phase gates fbr two trapped ions via adiabatic passage of dark states. During the operation, the vibrational mode is only virtually excited, thus the scheme is insensitive to heating. Furthermore, the spontaneous emission is suppressed since the ions are always in the electronic ground states. The scheme is robust against small fluctuations of parameters, and the conditional phase is tunable.     

Modelling the sensitivity of infrared emissivity of magnetic thin films to giant magnetoresistance

The correlation between emissivity and giant magnetoresistance (GMR) in magnetic thin films is investigated at infrared (IR) wavelengths using a thin-film model of emissivity. The sensitivity of emissivity to GMR is shown to depend upon film thickness, and agrees excellently with bulk-material results for films thicker than the material skin depth. However, for films thinner than the skin depth the sensitivity to GMR is shown to weaken. In addition, at mid-to-far IR wavelengths the spectral dependence of the correlation is investigated using a modified Drude-type expression for the refractive index combined with the thin-film model. This is applied to a multilayered GMR material, and the sensitivity of emissivity to GMR is shown to have a similar spectral dependence to that of the magnetorefractive effect. An analytical interpretation in terms of skin depth is also developed at long wavelengths, and shown to agree excellently with thin-film simulations.     

Quantum Thermal Transport through Extremely Cold Dielectric Chains

In the framework of Green＇s function theory out of equilibrium, a Landauer-Buttiker （LB） formula for thermal conductance is derived. A simplified model for describing extremely cold dielectric chains is proposed for the first time. Further we apply the present LB formula for studying thermal conductance at low-lying modes, emerging in dielectric atom chains. We find that quantum thermal conductance undergoes an anomalous transition due to new quasiparticle excitations, resulting from nonlinear atom-atom interactions. This theoretical prediction is in excellent agreement with a high-accuracy measurement to thermal conductance quantum.     

Suppression of Chaos and Phase Locking in Two Coupled Nonidentical Neurons under Periodic Input

Dynamical behaviour of two coupled neurons with at least one of them being chaotic is presented. Bifurcation diagrams and Lyapunov exponents are calculated to diagnose the dynamical behaviour of the coupled neurons with the increasing coupling strength. It is found that when the coupling strength increases, a chaotic neuron can be controlled by the coupling between neurons. At the same time, phase locking is studied by the maxima of the differences of instantaneous phases and average frequencies between two coupled neurons, and the inherent connection of phase locking and the suppression of chaos is formulated. It is observed that the onset of phase locking is closely related to the suppression of chaos. Finally, a way for suppression of chaos in two coupled nonidentical neurons under periodic input is suggested.     

Nuclear Effects in Structure Functions xFa（x, Q^2） from Charge Current Neutrino Deep Inelastic Scattering

By taking advantage of the model-independent nuclear parton distributions, the structure functions xF3（x, Q^2） are calculated, in comparison with the experimental data from CCFR neutrino-nuclei charge current deep inelastic scattering. It is shown that shadowing and anti-shadowing effects occur in valence quark distributions for small and medium x regions, respectively. It is suggested that the neutrino experimental data should be employed in the future for pinning down the nuclear patton distributions.     

A semi-analytical model for predicting multiple propagating axially symmetric modes in cylindrical waveguides

A semi-analytical model for multiple mode axially symmetric wave propagation in finite solid cylindrical waveguides is presented. The model is designed as a tool for predicting and interpreting experimental signals. The model is based on a common experimental configuration and considers the excitation, propagation and reception of the ultrasonic signal in the waveguide. The Pochhammer-Chree solution for an infinite cylinder is the basis for the model. Extensions are made to enable comparison to experimental results. Comparisons with experiment are performed in the time, frequency and joint-time frequency domain for both narrow band and broad band excitation of the piezo-electric transducer.     

Resonant ultrasound spectroscopy and homogeneity in polycrystals

Resonant ultrasound spectroscopy (RUS) is capable of determining the bulk elastic properties of a solid from its characteristic vibration frequencies, given the dimensions, density and shape of the sample. The model used for extracting values of the elastic constants assumes perfect homogeneity, which can be approximated by average-isotropic polycrystals. This approximation is excellent in the small grain regime assumed for most averaging procedures, but for real samples with indeterminate grain size distributions, it is not clear where the approximation breaks down. RUS measurements were made on pure copper samples where the grain size distribution was changed by progressive heat treatments in order to find a quantitative limit for the loss of homogeneity. It is found that when a measure of the largest grains is 15% of the sample’s smallest dimension, the deviation in RUS fits indicates elastic inhomogeneity.     

Locality Violation with Spin-Type W States without Using Inequalities

Using even and odd coherent states, we define a new state, which is called the spin-type W state. With the spin-type W states, we provide a new scheme for testing fundamental aspects of quantum mechanics and refuting local hidden variable theory without using inequalities. Finally, a scheme for preparing the spin-type W states, and discussion of experimental possibility and the effect of the measurement on physical observables due to a close orthogonality of the two coherent states are given.     

Note on wavefront dislocation in surface water waves

At singular points of a wave field, where the amplitude vanishes, the phase may become singular and wavefront dislocation may occur. In this Letter we investigate for wave fields in one spatial dimension the appearance of these essentially linear phenomena. We introduce the Chu-Mei quotient as it is known to appear in the ‘nonlinear dispersion relation’ for wave groups as a consequence of the nonlinear transformation of the complex amplitude to real phase-amplitude variables. We show that unboundedness of this quotient at a singular point, related to unboundedness of the local wavenumber and frequency, is a generic property and that it is necessary for the occurrence of phase singularity and wavefront dislocation, while these phenomena are generic too. We also show that the ‘soliton on finite background’, an explicit solution of the NLS equation and a model for modulational instability leading to extreme waves, possesses wavefront dislocations and unboundedness of the Chu-Mei quotient.     

Electron self-trapping at quantum and classical critical points

Using Feynman path integral technique estimations of the ground state energy have been found for a conduction electron interacting with order parameter fluctuations near quantum critical points. In some cases only singular perturbation theory in the coupling constant emerges for the electron ground state energy. It is shown that an autolocalized state (quantum fluctuon) can be formed and its characteristics have been calculated depending on critical exponents for both weak and strong coupling regimes. The concept of fluctuon is considered also for the classical critical point (at finite temperatures) and the difference between quantum and classical cases has been investigated. It is shown that, whereas the quantum fluctuon energy is connected with a true boundary of the energy spectrum, for classical fluctuon it is just a saddle-point solution for the chemical potential in the exponential density of states fluctuation tail.     

Spin squeezing in the presence of dissipation

The transfer of spin between photons and localized atomic levels, for a chain of two-level atoms, is studied. The Hamiltonian of the system is modelled by a radiation term and by atom-atom and radiation-atom interactions. Effects due to dissipation are accounted for by atom-photon exchange-interactions of complex strength. It is found that the spin-squeezing is suppressed by dissipation. Calculations are performed for arrays of Rb atoms excited by a GaAlAs laser.     

High-Power Extracavity Pulse Compression in Solid Materials

A novel technique for high-power extracavity pulse compression with a nonlinear solid material is demonstrated. Before spectral broadening by self-phase modulation in the solid material, a short filament generated in argon is used as a spatial filter, which works for a uniform spectrum broadening over the spatial profile. Compensated by chirped mirrors, a 15-fs pulse is generated from a 32-fs input laser pulse. A total transmission larger than 80% after the solid material is achieved.     

The role of atomic hydrogen in pre-epitaxial silicon substrate cleaning

The cleaning of silicon (Si) surfaces is a very important issue for the fabrication of novel semiconductor devices on the nanoscale. Established methods for the removal of organic impurities and the native or chemical oxide are often combined with high temperature desorption steps. However, devices with small feature sizes will be unfunctional if, for example, out-diffusion of dopants is not prevented. In this paper we present two possible processes for low-temperature cleaning: an atomic hydrogen source, based on dissociative adsorption of hydrogen at a heated tantalum (Ta) surface and a hydrogen DC plasma source as a part of an UHV cluster tool. The influence of atomic hydrogen on carbon and oxide removal is surveyed and the existing model for native oxide etching with an argon/hydrogen DC plasma is adapted.     

Spin-charge Separation of the Luttinger Model after an Interaction Quench

A Luttinger model of spin-1/2 fermions is considered after the interaction is suddenly switched on at time t = 0. By means of the bosonization technique, we evaluate analytically the one-particle correlation functions in detail, mainly involving equal-time correlations and propagators. The critical exponent which governs the power-law behavior of equal-time correlations for this spinful non-equilibrium system is obtained. In comparison with the published results, the difference between critical exponents of correlations in spinful and spinless non-equilibrium systems is found and explained. Furthermore, it is found that the propagator exhibits different power-law behavior from other equal-time correlations in this non-equilibrium system.     

Self-similar factor approximants for evolution equations and boundary-value problems

The method of self-similar factor approximants is shown to be very convenient for solving different evolution equations and boundary-value problems typical of physical applications. The method is general and simple, being a straightforward two-step procedure. First, the solution to an equation is represented as an asymptotic series in powers of a variable. Second, the series are summed by means of the self-similar factor approximants. The obtained expressions provide highly accurate approximate solutions to the considered equations. In some cases, it is even possible to reconstruct exact solutions for the whole region of variables, starting from asymptotic series for small variables. This can become possible even when the solution is a transcendental function. The method is shown to be more simple and accurate than different variants of perturbation theory with respect to small parameters, being applicable even when these parameters are large. The generality and accuracy of the method are illustrated by a number of evolution equations as well as boundary value problems.     

Ionization Energies of Ions in Hot and Dense Plasma: Beryllium-Like Ions for Z=26-36

Ionization energies of beryllium-like ions for Z = 26 - 36 in hot ana aense plasmas （ne=10^22 -10^24 cm^-3,kT= 500 - 2000 eV） are obtained by using an approach developed for electronic structure and transition property of ions in hot and dense plasmas based on the multi-configuration Dirac-Fock model. Influence of the plasma environment is considered by introducing a correction to the one-electron potential to account for the screening of the ionized electrons. This correction is calculated from the ionized electron micro-space distribution, which is obtained based on an ＂average atom model for the temperature and density-dependent average ionization of atoms in plasmas. Comparison between the present and the ion sphere models is made to display the significance of the ionized electron micro-space distribution.     

A method to simulate linear stability of impulsively accelerated density interfaces in ideal-MHD and gas dynamics

We present a numerical method to solve the linear stability of impulsively accelerated density interfaces in two dimensions such as those arising in the Richtmyer–Meshkov instability. The method uses an Eulerian approach, and is based on an upwind method to compute the temporally evolving base state and a flux vector splitting method for the perturbations. The method is applicable to either gas dynamics or magnetohydrodynamics. Numerical examples are presented for cases in which a hydrodynamic shock interacts with a single or double density interface, and a doubly shocked single density interface. Convergence tests show that the method is spatially second-order accurate for smooth flows, and between first and second-order accurate for flows with shocks.     

On dynamics of velocity vector potential in incompressible fluids

An elegant quaternionic formulation is given for the Lagrangian advection equation for velocity vector potential in fluid dynamics. At first we study the topological significance of a restricted conserved quantity viz., stream-helicity and later more realistic configuration of open streamlines is figured out. Also, using Clebsch parameterisation of the velocity vector potential yet another physical significance for the stream-helicity is provided. Finally we give a Nambu-Poisson formalism of the Lagrangian advection equation for velocity vector potential.     

Zero frequency shift of an oscillating-rotating liquid droplet

Free-decay oscillations and rotations of a levitated liquid droplet are simulated numerically, and the frequency shift of drop-shape oscillations is studied. It is shown for an oscillating-rotating liquid droplet that the oscillation frequency decreases as the amplitude of drop-shape oscillations increases, while it increases as the rotation rate increases. The pressure difference between the equator and the pole of the droplet is found to correspond to the frequency shift. It is also found that the relation between the amplitude and the rotation rate is linear both for zero frequency shift and for zero pressure difference.