11,394 research outputs found
Dynamical Realization of Macroscopic Superposition States of Cold Bosons in a Tilted Double Well
We present exact expressions for the quantum sloshing of Bose-Einstein
condensates in a tilted two-well potential. Tunneling is suppressed by a small
potential difference between wells, or tilt. However, tunneling resonances
occur for critical values of the tilt when the barrier is high. At resonance,
tunneling times on the order of 10-100 ms are possible. Furthermore, such
tilted resonances lead to a dynamical scheme for creating few-body NOON-like
macroscopic superposition states which are protected by the many body
wavefunction against potential fluctuations.Comment: 6 pages, 5 figures, final version, only minor changes from previous
arXiv versio
Statistical correlations of an anyon liquid at low temperatures
Using a proposed generalization of the pair distribution function for a gas
of non-interacting particles obeying fractional exclusion statistics in
arbitrary dimensionality, we derive the statistical correlations in the
asymptotic limit of vanishing or low temperature. While Friedel-like
oscillations are present in nearly all non-bosonic cases at T=0, they are
characterized by exponential damping at low temperature. We discuss the
dependence of these features on dimensionality and on the value of the
statistical parameter alpha.Comment: to appear in Phys. Chem. Liquid
Spatial fluctuations in an optical parametric oscillator below threshold with an intracavity photonic crystal
We show how to control spatial quantum correlations in a multimode degenerate
optical parametric oscillator type I below threshold by introducing a spatially
inhomogeneous medium, such as a photonic crystal, in the plane perpendicular to
light propagation. We obtain the analytical expressions for all the
correlations in terms of the relevant parameters of the problem and study the
number of photons, entanglement, squeezing, and twin beams. Considering
different regimes and configurations we show the possibility to tune the
instability thresholds as well as the quantumness of correlations by breaking
the translational invariance of the system through a photonic crystal
modulation.Comment: 12 pages, 7 figure
Cryogenic Ion Trapping Systems with Surface-Electrode Traps
We present two simple cryogenic RF ion trap systems in which cryogenic
temperatures and ultra high vacuum pressures can be reached in as little as 12
hours. The ion traps are operated either in a liquid helium bath cryostat or in
a low vibration closed cycle cryostat. The fast turn around time and
availability of buffer gas cooling made the systems ideal for testing
surface-electrode ion traps. The vibration amplitude of the closed cycled
cryostat was found to be below 106 nm. We evaluated the systems by loading
surface-electrode ion traps with Sr ions using laser ablation, which
is compatible with the cryogenic environment. Using Doppler cooling we observed
small ion crystals in which optically resolved ions have a trapped lifetime
over 2500 minutes.Comment: 10 pages, 13 EPS figure
Phase transitions near black hole horizons
The Reissner-Nordstrom black hole in four dimensions can be made unstable
without violating the dominant energy condition by introducing a real massive
scalar with non-renormalizable interactions with the gauge field. New stable
black hole solutions then exist with greater entropy for fixed mass and charge
than the Reissner-Nordstrom solution. In these new solutions, the scalar
condenses to a non-zero value near the horizon. Various generalizations of
these hairy black holes are discussed, and an attempt is made to characterize
when black hole hair can occur.Comment: 30 pages, 6 figures. v2: minor corrections, references adde
A Three Dimensional Lattice of Ion Traps
We propose an ion trap configuration such that individual traps can be
stacked together in a three dimensional simple cubic arrangement. The isolated
trap as well as the extended array of ion traps are characterized for different
locations in the lattice, illustrating the robustness of the lattice of traps
concept. Ease in the addressing of ions at each lattice site, individually or
simultaneously, makes this system naturally suitable for a number of
experiments. Application of this trap to precision spectroscopy, quantum
information processing and the study of few particle interacting system are
discussed.Comment: 4 pages, 4 Figures. Fig 1 appears as a composite of 1a, 1b, 1c and
1d. Fig 2 appears as a composite of 2a, 2b and 2
Kinetic Energy Density Study of Some Representative Semilocal Kinetic Energy Functionals
There is a number of explicit kinetic energy density functionals for
non-interacting electron systems that are obtained in terms of the electron
density and its derivatives. These semilocal functionals have been widely used
in the literature. In this work we present a comparative study of the kinetic
energy density of these semilocal functionals, stressing the importance of the
local behavior to assess the quality of the functionals. We propose a quality
factor that measures the local differences between the usual orbital-based
kinetic energy density distributions and the approximated ones, allowing to
ensure if the good results obtained for the total kinetic energies with these
semilocal functionals are due to their correct local performance or to error
cancellations. We have also included contributions coming from the laplacian of
the electron density to work with an infinite set of kinetic energy densities.
For all the functionals but one we have found that their success in the
evaluation of the total kinetic energy are due to global error cancellations,
whereas the local behavior of their kinetic energy density becomes worse than
that corresponding to the Thomas-Fermi functional.Comment: 12 pages, 3 figure
Magnetic order in GdBiPt studied by x-ray resonant magnetic scattering
Rare earth (R) half-Heusler compounds, RBiPt, exhibit a wide spectrum of
novel ground states. Recently, GdBiPt has been proposed as a potential
antiferromagnetic topological insulator (AFTI). We have employed x-ray resonant
magnetic scattering to elucidate the microscopic details of the magnetic
structure in GdBiPt below T_N = 8.5 K. Experiments at the Gd L_2 absorption
edge show that the Gd moments order in an antiferromagnetic stacking along the
cubic diagonal [1 1 1] direction satisfying the requirement for an AFTI, where
both time-reversal symmetry and lattice translational symmetry are broken, but
their product is conserved.Comment: 4 pages, 4 figure
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