Generation of Entangled Multi-atom Dicke States in Cavity Quantum Electrodynamics

We propose a scheme to generate two-atom maximally entangled state in cavity quantum electrodynamies （QED）. The scheme can 5e extended to generation of entangled multi-atom Dicke states if we control the interaction time of atoms with cavity modes. We use adiabatically state evolution under large atom-cavity detuning, so the scheme is insensitive to atomic spontaneous decay. The influence of cavity decay on fidelity and success probability is discussed.     

The equilibrium thermodynamics of a spin-boson model

We consider the equilibrium thermodynamics of a Dicke-type model forN identical spins of arbitrary magnitude interacting linearly and homogeneously with a boson field in a volumeV _N, in the limitN,V _N, withN/V _N=const. The system exhibits a second-order phase transition; complete information on the spin polarizations and their correlations is obtained. The proofs use a general result on the free energy of quantum spin systems based on the large deviation principle and the Berezin-Lieb inequalities.     

Holographic dark energy in Brans–Dicke cosmology with chameleon scalar field

We study a cosmological implication of holographic dark energy in the Brans–Dicke gravity. We employ the holographic model of dark energy to obtain the equation of state for the holographic energy density in non-flat (closed) universe enclosed by the event horizon measured from the sphere of horizon named L. Our analysis shows that one can obtain the phantom crossing scenario if the model parameter α (of order unity) is tuned accordingly. Moreover, this behavior is achieved by treating the Brans–Dicke scalar field as a Chameleon scalar field and taking a non-minimal coupling of the scalar field with matter. Hence one can generate phantom-like equation of state from a holographic dark energy model in non-flat universe in the Brans–Dicke cosmology framework.     

Holographic Principle of Black Holes in Brans–Dicke Theory

Brans type-I black holes is a peculiar spherically symmetric solution found in geometrized gravity theories, since the azimuthal factor of its horizon is divergent or vanishing under the classical approach of r = 2M. However, if we regard that the spherically symmetric solution is available only when all physical quantities of black holes are meaningful, then our investigation would be restricted to a special range of parameters and hence indicate a definite holographic relation to type-I black holes in Brans–Dicke theory. After that, we are able to investigate this holographic relation by making use of the brick-wall method. Drawn a comparison between the arising result and a simulated entropy formula derived from the thermodynamical evolution, a variable cut-off factor α of Brans type-I black holes is ultimately carried out.     

String Cosmology in Brans–Dicke Theory for Kasner Type Metric

For a string Bianchi type-I metric of Kasner form in Brans–Dicke theory of gravity, it is not possible to describe an anisotropic physical model of the universe.     

Phase dependence of collective fluorescence via interferences from incoherent pumping

We investigate the resonance fluorescence from a collection of three-level V- or Λ-type atoms which are driven simultaneously by coherent and incoherent sources of light. In particular, we focus on interference effects arising from broadband incoherent pump fields. This interference, which does not require non-orthogonal transition dipole moments, induces a sensitivity to the relative phase of the coherent driving fields. It is shown that the variation of the relative phase leads to interesting modifications of the collective steady-state behaviors of the two systems.     

Dressing method in matter+radiation quantum models

We consider spectral problems related to Dicke and Jaynes-Cummings matter-radiation Hamiltonians and write the spectrum of a perturbed Dicke model (of a trapped ion interacting with the center-of-mass motion) in explicit form. We derive the dressing chain equations for non-Abelian elements and investigate them for two-state matter models. We discuss embedding of Jaynes-Tavis-Cummings models and nonrotating wave terms. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 152, No. 1, pp. 118–132, July, 2007.     

Lineshapes of the 172 and 602 GHz rotational transitions of HCN

Experimental lineshapes of the 172 and 602 GHz millimeter lines of HC¹⁵N in collision with H₂, N₂, O₂, CH₃CN and some rare gases are studied for the purpose of atmospheric applications and detailed collision analysis. Using of a sensitive frequency modulation technique allows highlighting clear deviations from the usual Voigt profile, these departures being generally considered as related to molecular diffusion effects or to the dependence of collisional relaxation rates on molecular speeds. Except the light buffer gases H₂ and He, the linefits using the Galatry profile lead to nonlinear pressure dependencies of relaxation rates, that rules out the frequent hypothesis of an exclusive role of molecular diffusion (Dicke effect). This observation is shown to be in accordance with the fact that optical radii related to relaxation are usually greater than kinetic Lennard-Jones radii tied to diffusion. In contrast, the actual lineshapes are well reproduced by the Speed-Dependent Voigt profile taking into account the speed dependence of relaxation rates which display linear pressure dependencies. For the particular cases of the N₂- and Ar-HCN pairs, the experimental results are rather well explained by semi-classical computations based on the Robert–Bonamy formalism improved by the model of exact trajectories. These computations show that relaxation rates are proportional to some power of the colliders’ relative speed. A detailed comparison of relaxation parameters deduced from low-pressure experiments with Galatry and Speed-Dependent Voigt profiles allows to infer that the optical diffusion rates are much smaller that kinetic ones, so that the experimental lineshapes depend nearly exclusively on the speed dependence of relaxation rates and are weakly affected by molecular diffusion effects. Extension of these conclusions to other molecules of atmospheric interest is discussed. Finally, an appendix presents unpublished results dealing with the collisional relaxation of some rotational lines of HC¹⁵N (at 258 GHz for different temperatures and at 344 GHz) and HC¹⁴N (at 355 GHz).     

A Geometrical Interpretation of Grassmannian Coordinates

A geometrical interpretation of Grassmannian anticommuting coordinates is given. They are taken to represent an indefiniteness inherent in every spacetime point on the level of the spacetime foam. This indeterminacy is connected with the fact that in quantum gravity in some approximation we do not know the following information: are two points connected by a quantum wormhole or not? It is shown that: (a) such indefiniteness can be represented by Grassmannian numbers, (b) a displacement of the wormhole mouth is connected with a change of the Grassmannian numbers (coordinates). In such an interpretation of supersymmetry the corresponding supersymmetrical fields must be described in an invariant manner on the background of the spacetimefoam.