Dynamics of quantum steerability for two atoms in coupled cavities

We study the dynamics of quantum steerability between two non-interacting atoms, each of which is trapped inside one of two coupled cavities. Compared with entanglement, quantum steerability manifests sudden birth and sudden death phenomenon during the time evolution. We find that the cavity decay plays a destruction role for both steerability and entanglement. It is also shown that the survival time as well as the maximal value of steerability are sensitive to the asymmetry of the cavities. Moreover, it is found the sudden death of steerability can be controlled by the hopping rate of the coupled cavities.     

Generating squeezed states by strong laser-atom interaction

Abstract

A proof is given using, a quantized single mode field in interaction with an atom in non-relativistic approximation, that the scattered light in strong laser–atom interaction can be made coherent to squeezed by properly choosing the wavelength of the laser, the density of the sample of atoms at the laser beam and the pulse duration. In the experiments with gases for harmonic generation, at the current laser wavelengths this effect is too small to be observed and the term of the square of the field in the Hamiltonian can be safely neglected. Then, the observed light is purely coherent.     

On the principles of vortex localization and motion in superconductor thin films with artificially patterned cavities

In this paper we summarize the results of our recent studies of vortex matter in high-T_c superconductors with antidots, i.e. lithographically patterned holes in superconductor thin films. We analyze theoretically and experimentally the distribution of magnetic flux and effective pinning energy in perforated samples: the equilibrium occupation number (number of flux quanta accomodated by the hole) is evaluated numerically in a range of temperatures and fields for antidot sizes typically used in experiments; magnetic field profiles and activation energy of thermally activated flux creep is obtained from magnetic relaxation measurements by the means of Hall probes array. Possible mechanisms of vortex penetration and propulsion in such structures are discussed.     

The dynamics of entanglement and quantum discord of two atoms in coupled cavities

We investigate the dynamics of quantum correlations such as entanglement and quantum discord between two noninteracting atoms, each of which is trapped inside one of two coupled cavities. We find that the cavity decay can induce both entanglement and quantum discord between the two atoms when they are initially prepared in doubly excited state. The result shows the sudden death and sudden birth of entanglement and robustness of the quantum discord to sudden death. It is also found that the doubly excited state is responsible for the sudden death of entanglement. Moreover, the sudden death of entanglement can be controlled by the intercavity hopping rate.     

Fragmentation of protonated peptide ions via interaction with metastable atoms

Fragmentation of protonated peptide ions via interaction with low kinetic energy electronicallyexcited metastable argon atoms was studied in a linear trap-time-of-flight mass spectrometer. Metastable argon atoms were generated using a glow discharge-type source. Protonated peptide ions of substance P, bradykinin, fibrinopetide A, and insulin oxidized chain B were produced by electrospray ionization and trapped in a quadrupole ion guide for 100-400 ms. Intensive series of c- and z-ions were observed in all cases. The kinetic measurements of the fragmentation rates are consistent with calculations of the reaction cross section based on the Landau-Zener approximation.     

An investigation of the motion of homogeneous and stratified liquids in rectangular cavities by the method of photochromic visualization

A method of photochromic visualization has been developed for investigating thermogravitational flows in homogeneous and stratified fluids in a closed volume.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 58, No. 5, pp. 760–766, May, 1990.     

Electron states of europium atoms on the oxidized tungsten surface

The charge state of europium (Eu) atoms adsorbed on the oxidized tungsten surface is evaluated. An energy band diagram of the adsorption system is proposed for large and small Eu coverages. The adsorption energy of Eu atoms is estimated.     

Scattering matrix approach to the resonant states and Q values of microdisk lasing cavities

We develop a scattering matrix approach for the numerical calculation of resonant states and Q values of a nonideal optical disk cavity with an arbitrary shape and with an arbitrary varying refraction index. The developed method is applied to study the effect of surface roughness and inhomogeneity of the refraction index on Q values of microdisk cavities for lasing applications. We demonstrate that even small surface roughness (deltar < or approximately equal to lambda/50) can lead to a drastic degradation of high-Q cavity modes by many orders of magnitude. The results of the numerical simulation are analyzed and explained in terms of wave reflection at a curved dielectric interface, combined with an examination of Poincaré surfaces of section and of Husimi distributions.     

Dynamic interaction of neutral atoms with crystal surface at grazing incidence

Dynamic effects that have been recently discovered in the rainbow scattering of neutral atoms from crystal surfaces at grazing incidence are interpreted. It is shown that these features can be explained by the electron drag of scattered atomic particles near the crystal surface.     

Preparation of W,GHZ, and two-qutrit states using bimodal cavities

Abstract

We show how one can prepare three-qubit entangled states like W-states, Greenberger-Horne-Zeilinger states as well as two-qutrit entangled states using the multi-atom two-mode entanglement. We propose a technique of preparing such a multi-particle entanglement using stimulated Raman adiabatic passage. We consider a collection of three-level atoms in Λ configuration simultaneously interacting with a resonant two-mode cavity for this purpose. Our approach permits a variety of multi-particle extensions.     

Statistical properties of finite-bandwidth radiation scattered by random amplitude screens and random phase screens

We investigate the effect of finite bandwidth of the incident radiation on scattering by thin layers that introduce random phase or amplitude variations. In particular, we calculate the scintillation index of the propagating radiation for smoothly varying and fractal phase screens and for random telegraph wave and checkerboard amplitude screens. Increasing the bandwidth of the incident radiation reduces the fluctuations of the scattered intensity over the whole propagation path, except in the case of the smoothly varying phase screen, where geometrical optics features in the pattern persist in the focusing region.     

Nonlinear motion of crack tip atoms during cleavage processes

Nonlinear features of cleavage processes under mode I loading are explored from an atomic scale. Crack tip atom string models coupling with the continuum mechanics analysis are devised. As the stress intensity factor increases, dynamic analysis shows that the atom motion at a crack tip changes from quasi-periodic to chaotic and back to quasi-periodic. The chaotic atom motion characterizes a cleavage precursor in which the inter-atomic bond disintegrates under certain adhesion.     

Nanostructured lanthanum cobaltate: oxidation and coordination states of Co atoms

Lanthanum cobaltate (LaCoO _x ) nanostructured inside the MCM-41 mesoporous molecular sieve as well as in the bulk LaCoO₃ perovskite were characterised by SAXS, ESR, UV–vis DRS, EXAFS and XPS techniques. The nanosized LaCoO _x particles stabilised within the mesopores of MCM-41 matrix containing Co atoms in rather low average oxidation state, which is not characteristic of bulk LaCoO₃ perovskites. Meanwhile, the coordination states of Co in both cases are quite similar. Also, the concentration of Co(II) cations in cobaltate nanoparticles was found to be twice as in bulk LaCoO₃ material. The supported cobaltate does not form short-range ordered species of LaCoO₃ in the MCM-41 matrix but presents as the highly disordered, oxygen-deficient Co oxide nanophase which is probably to be stabilised by La ions present.     

Thermodynamics of the interaction between impurity atoms and a system of quantum dots

Thermodynamics of the process of dissolution of impurity atoms in a system of quantum dots is analyzed based on minimization of the Gibbs free energy. Criteria for the effective introduction of single impurity atoms into quantum dots are formulated.

     

Instrumentation for multistep excitation of lithium atoms to Rydberg states

We have developed a diode laser apparatus to excite Li from its ground 2S state, through 2P and 3S, to its Rydberg states with three cw diode lasers operating at λ = 671 nm, 813 nm, and 630-635 nm. A He-Ne laser at λ = 633 is sometimes used in place of the 635-nm diode laser for the last step. The output power of each of these lasers was ~1 mW. We describe our technique of locking the first two lasers on Li resonance lines by obtaining a fluorescent signal from the second decay (3S ? 2P) that is normally overpowered by a strong background of fluorescent light from the first decay (2P ? 2S). We used two balanced photodiodes to reject the strong fluorescent light without loss of collection efficiency. A rejection ratio as high as 100 has been obtained.     

Dichroism and birefringence in aperiodic coupled cavities and their influence on the polarization states of quasi-isotropic lasers

We show that aperiodic coupled cavities may be designed to have a frequency-dependent complex reflectance that is anisotropic in phase (birefringent) and in amplitude (dichroic). The complex mean or average reflectivity may also be frequency dependent. As an illustration we show how such multicavity effects influence the stability of the polarization of light in quasi-isotropic lasers. Possible applications of the properties of aperiodic coupled cavities are suggested.     

First-principles molecular dynamics simulation on interatomic interaction of Fe crystal with Pb and Bi atoms

The interaction mechanism between Fe crystals and Pb and Bi atoms was investigated using the first-principles molecular dynamics theory based on the density functional theory, which was the first step of an analytical approach to the simulation of steel corrosion in high temperature lead–bismuth (Pb–Bi) cooled fast breeder reactors and accelerator driven systems. The Vanderbilt ultrasoft pseudopotentials for Fe, Pb and Bi elements were calculated with the exchange and correlation corrections by the local density approximation. Crystal lattice constants calculated using the potentials agreed well with experimental ones. Using the calculated pseudopotentials, the first-principles molecular dynamics simulations were performed to investigate the interatomic interaction between Fe crystal and Pb, Bi atoms. The result shows the reasonable motions of Pb and Bi atoms near the surface of the Fe crystal and those of Fe atoms in the crystal.