Matt's arXiv selection: week ending 1 August 2008

From: Matthew Davis <>
Date: Tue, 26 Aug 2008 08:26:20 +1000

The following message was sent to the matts_arxiv list by Matthew Davis <>

Hi everyone,

A combination of illness and lectures have meant that I've fallen well behind.
In the last week of July there were 28 new preprints and 6 replacements.

Date: Fri, 25 Jul 2008 02:40:20 GMT (97kb)

Title: Localized gap soliton trains of Bose-Einstein condensates in an optical
Authors: D. L. Wang, X. H. Yan, W. M. Liu
Categories: cond-mat.other
Comments: 9 pages, 6 figures, accepted for publicaiton in PRE
   We develop a systematic analytical approach to study the linear and nonlinear
solitary excitations of quasi-one-dimensional Bose-Einstein condensates trapped
in an optical lattice. For the linear case, the Bloch wave in the $nth$ energy
band is a linear superposition of Mathieu's functions $ce_{n-1}$ and $se_n$;
and the Bloch wave in the $nth$ band gap is a linear superposition of $ce_n$
and $se_n$. For the nonlinear case, only solitons inside the band gaps are
likely to be generated and there are two types of solitons -- fundamental
solitons (which is a localized and stable state) and sub-fundamental solitons
(which is a lacalized but unstable state). In addition, we find that the
pinning position and the amplitude of the fundamental soliton in the lattice
can be controlled by adjusting both the lattice depth and spacing. Our
numerical results on fundamental solitons are in quantitative agreement with
those of the experimental observation [Phys. Rev. Lett. {\bf92}, 230401
(2004)]. Furthermore, we predict that a localized gap soliton train consisting
of several fundamental solitons can be realized by increasing the length of the
condensate in currently experimental conditions.
\\ ( , 97kb)
Date: Fri, 25 Jul 2008 11:29:14 GMT (26kb)

Title: Geometric potentials in quantum optics: A semi-classical interpretation
Authors: Marc Cheneau (LKB - Lhomond), Steffen Patrick Rath (LKB - Lhomond),
   Tarik Yefsah (LKB - Lhomond), Kenneth John G\"unter (LKB - Lhomond),
   Gediminas Juzeliunas, Jean Dalibard (LKB - Lhomond)
Categories: cond-mat.other
Comments: 6 pages 1 figure
   We propose a semi-classical interpretation of the geometric scalar and vector
potentials that arise due to Berry's phase when an atom moves slowly in a light
field. Starting from the full quantum Hamiltonian, we turn to a classical
description of the atomic centre-of-mass motion while still treating the
internal degrees of freedom as quantum variables. We show that the scalar
potential can be identified as the kinetic energy of an atomic micro-motion
caused by quantum fluctuations of the radiative force, and that the
Lorentz-type force appears as a result of the motion-induced perturbation of
the internal atomic state. For a specific configuration involving two
counter-propagating Gaussian laser beams, we relate the geometric forces to the
radiation pressure and dipole forces known from quantum optics. The simple
physical pictures provided by the present analysis may help for the design and
the implementation of novel geometric forces.
\\ ( , 26kb)
Date: Fri, 25 Jul 2008 16:50:26 GMT (50kb)

Title: Gutzwiller approach to the Bose-Hubbard model with random local
Authors: P. Buonsante, F. Massel, V. Penna and A. Vezzani
Categories: cond-mat.dis-nn
Comments: 12 pages, 5 figures
   Recently it has been suggested that fermions whose hopping amplitude is
quenched to extremely low values provide a convenient source of local disorder
of lattice bosonic systems realized in current experiment on ultracold atoms.
Here we investigate the phase diagram of such systems, which provide the
experimental realization of a Bose-Hubbard model whose local potentials are
randomly extracted from a binary distribution. We adopt a site-dependent
Gutzwiller description of the state of the system, and obtain results agreeing
with previous findings, as far as the compressibility of the system is
concerned. We discuss the expected peaks in the experimental excitation
spectrum of the system, related to the incompressible phases, and the
superfluid character of the {\it partially compressible phases} characterizing
the phase diagram of systems with binary disorder. In our investigation we make
use of several analytical results whose derivation is described in the
appendices, and whose validity is not limited to the system under concern.
\\ ( , 50kb)
Date: Fri, 25 Jul 2008 13:40:08 GMT (432kb)

Title: Magneto optical trapping of Barium
Authors: S. De, U. Dammalapati, K. Jungmann, L. Willmann
Categories: physics.atom-ph
Comments: 4 pages, 5 figures
   First laser cooling and trapping of the heavy alkaline earth element barium
has been achieved based on the strong 6s$^2$ $^1$S$_0$ - 6s6p $^1$P$_1$
transition for the main cooling. Due to the large branching into metastable
D-states several additional laser driven transitions are required to provide a
closed cooling cycle. A total efficiency of $0.4(1) \cdot 10^{-2}$ for slowing
a thermal atomic beam and capturing atoms into a magneto optical trap was
obtained. Trapping lifetimes of more than 1.5 s were observed. This lifetime is
shortened at high laser intensities by photo ionization losses. The developed
techniques will allow to extend significantly the number of elements that can
be optically cooled and trapped.
\\ ( , 432kb)
arXiv:0807.4022 (*cross-listing*)
Date: Fri, 25 Jul 2008 08:29:56 GMT (1380kb,D)

Title: Stark deceleration of OH radicals in low-field-seeking and
   high-field-seeking quantum states
Authors: Kirstin Wohlfart, Frank Filsinger, Fabian Gr\"atz, Jochen K\"upper,
   Gerard Meijer
Categories: physics.chem-ph physics.atom-ph physics.ins-det
Comments: 8 pages, 9 figures
   The Stark deceleration of OH radicals in both low-field-seeking and
high-field-seeking levels of the rovibronic ${}^2\Pi_{3/2},v=0,J=3/2$ ground
state is demonstrated using a single experimental setup. Applying
alternating-gradient focusing, OH radicals in their low-field-seeking
${}^2\Pi_{3/2},v=0,J=3/2,f$ state have been decelerated from 345 m/s to 239
m/s, removing 50 % of the kinetic energy using only 27 deceleration stages. The
alternating-gradient decelerator allows to independently control longitudinal
and transverse manipulation of the molecules. Optimized high-voltage switching
sequences for the alternating-gradient deceleration are applied, in order to
adjust the dynamic focusing strength in every deceleration stage to the
changing velocity over the deceleration process. In addition we have also
decelerated OH radicals in their high-field-seeking ${}^2\Pi_{3/2},v=0,J=3/2,e$
state from 355 m/s to 316 m/s. For the states involved, a real crossing of
hyperfine levels occurs at 640 V/cm, which is examined by varying a bias
voltage applied to the electrodes.
\\ ( , 1380kb)
Date: Fri, 25 Jul 2008 20:39:00 GMT (11kb)

Title: Critical properties of 1D spin-gapped fermions at the onset of
Authors: T. Vekua, S.I. Matveenko, and G.V. Shlyapnikov
Categories: cond-mat.str-el
Comments: 4 revtex pages
   We develop an effective field theory for finding critical properties of 1D
spin gapped fermions at the onset of magnetization. It is shown how the
spin-charge interaction leads to a linear critical behavior and finite
susceptibility for a wide range of models. We also discuss possible
manifestations of spin-charge coupling in cold atomic gases.
\\ ( , 11kb)
Date: Sat, 26 Jul 2008 21:27:11 GMT (78kb)

Title: Dirac-point engineering and topological phase transitions in honeycomb
   optical lattices
Authors: B. Wunsch, F. Guinea, F. Sols
Categories: cond-mat.mes-hall
Comments: 10 pages, 5 figures
   We study the electronic structure and the phase diagram of non-interacting
fermions confined to hexagonal optical lattices. In the first part, we compare
the properties of Dirac points arising in the eigenspectrum of either honeycomb
or triangular lattices. Numerical results are complemented by analytical
equations for weak and strong confinements. In the second part we discuss the
phase diagram and the evolution of Dirac points in honeycomb lattices applying
a tight-binding description with arbitrary nearest-neighbor hoppings. With
increasing asymmetry between the hoppings the Dirac points approach each other.
At a critical asymmetry the Dirac points merge to open an energy gap, thus
changing the topology of the eigenspectrum. We analyze the trajectory of the
Dirac points and study the density of states in the different phases.
Manifestations of the phase transition in the temperature dependence of the
specific heat and in the structure factor are discussed.
\\ ( , 78kb)
Date: Mon, 28 Jul 2008 12:39:06 GMT (120kb)

Title: Phase separation in imbalanced fermion superfluids beyond mean-field
Authors: J. Tempere, S.N. Klimin, J.T. Devreese
Categories: cond-mat.other cond-mat.supr-con
Comments: 10 pages, 3 figures
   The density distributions of the two components of a trapped, ultracold Fermi
gas with population imbalance reveal the effect of imbalance on superfluid
pairing. We develop a path-integral derivation of the density, that takes into
account both fluctuations beyond mean-field and effects of nonzero temperature.
The calculated density profiles compare favorably to the measured density
profiles, and illustrate the necessity to incorporate both quantum fluctuations
and finite temperature effects. The temperature dependence of the density
profiles, especially near the superfluid-normal interface, allows determining
the temperature of the superfluid core in current experiments.
\\ ( , 120kb)
Date: Mon, 28 Jul 2008 17:32:34 GMT (979kb)

Title: Role of interactions in 87Rb-40K Bose-Fermi mixtures in a 3d optical
Authors: Th. Best, S. Will, U. Schneider, L. Hackermueller, D.-S. Luehmann, D.
   van Oosten, and I. Bloch
Categories: cond-mat.other
Comments: 5 pages, 4 figures
   We investigate the effect of interspecies interaction on a degenerate mixture
of bosonic 87Rb and fermionic 40K atoms in a three-dimensional optical lattice
potential. Using a Feshbach resonance, the 87Rb-40K interaction is tuned over a
wide range. Through an analysis of the 87Rb momentum distribution, we find a
pronounced asymmetry between strong repulsion and strong attraction. In the
latter case, the Bose-Hubbard parameters are renormalized due to self-trapping,
leading to a marked shift in the superfluid to Mott insulator transition with
increasing Bose-Fermi interaction.
\\ ( , 979kb)
Date: Sun, 27 Jul 2008 23:19:41 GMT (125kb)

Title: Rubidium resonant squeezed light from a diode-pumped optical-parametric
Authors: A. Predojevi\'c, Z. Zhai, J.M. Caballero, M.W. Mitchell
Categories: quant-ph
Comments: 6 pages 4 figures
   We demonstrate a diode-laser-pumped system for generation of quadrature
squeezing and polarization squeezing. Due to their excess phase noise, diode
lasers are challenging to use in phase-sensitive quantum optics experiments
such as quadrature squeezing. The system we present overcomes the phase noise
of the diode laser through a combination of active stabilization and
appropriate delays in the local oscillator beam. The generated light is
resonant to the rubidium D1 transition at 795nm and thus can be readily used
for quantum memory experiments.
\\ ( , 125kb)
Date: Mon, 28 Jul 2008 12:44:48 GMT (229kb)

Title: Detection of hidden entanglement by photon anti-bunching
Authors: Alessandro Fedrizzi, Thomas Herbst, Markus Aspelmeyer, Marco Barbieri,
   Thomas Jennewein, Anton Zeilinger
Categories: quant-ph
Comments: 5 pages, 3 figures
   Two-photon anti-bunching at a beamsplitter is only possible if the photons
are entangled in one specific state, anti-symmetric in the modes. Thus,
detection of anti-bunching is a direct indication of entanglement in a variable
which might not be directly accessible in an experiment, since the total state
of two photons must be symmetric. We demonstrate this explicitly quantitatively
in the case of frequency entanglement of two photons with continuous frequency
detunings. The principle of detecting hidden entanglement via anti-bunching at
a beamsplitter may facilitate the observation of entanglement in other systems,
like atomic ensembles or BECs. The analogue in fermionic systems would be to
observe bunching.
\\ ( , 229kb)
Date: Mon, 28 Jul 2008 13:09:45 GMT (330kb)

Title: Unusual decoherence in qubit measurements with a Bose-Einstein
Authors: D. Sokolovski and S.A. Gurvitz
Categories: quant-ph
Comments: 4 pages
   We consider an electrostatic qubit located near a Bose-Einstein condensate
(BEC) of noninteracting bosons in a double-well potential, which is used for
qubit measurements. Tracing out the BEC variables we obtain a simple analytical
expression for the qubit's density-matrix. The qubit's evolution exhibits a
slow ($\propto1/\sqrt{t}$) damping of the qubit's coherence term, in contrast
to the exponential damping produced by most classical detectors. The
decoherence is, in general, incomplete and strongly depends on the initial
state of the qubit. In the special case of a static qubit the suppression of
the coherence term is shown to be Gaussian in time.
\\ ( , 330kb)
Date: Mon, 28 Jul 2008 10:35:07 GMT (73kb)

Title: High-Precision Measurement of the Laser-Trapping Frequencies for
   $^{209,210,211}$Fr Atoms
Authors: S. Sanguinetti, R. Calabrese, L. Corradi, A. Dainelli, A. Khanbekyan,
   E. Mariotti, C. de Mauro, P. Minguzzi, L. Moi, G. Stancari, L. Tomassetti, S.
Categories: physics.atom-ph
Comments: 4 pages, 2 figures, 1 table
   We present the accurate measurement of the frequency of the $7S-7P$
laser-trapping transition for three francium isotopes. Our approach is based on
an interferometric comparison to deduce the unknown laser frequency from a
secondary laser frequency-standard. After careful investigation of systematics,
with samples of about 100 atoms the final accuracy reaches 8 MHz, an order of
magnitude better than the best previous measurement for $^{210}$Fr, and opens
the way to improved tests of the theoretical computation of Fr atomic
\\ ( , 73kb)
Date: Mon, 28 Jul 2008 20:02:01 GMT (43kb)

Title: Unconventional quantum phases of lattice bosonic mixtures
Authors: P. Buonsante, S. M. Giampaolo, F. Illuminati, V. Penna, A. Vezzani
Categories: cond-mat.other
Comments: 7 pages, 3 figures
   We discuss strongly interacting one-dimensional boson-boson mixtures and
study their quantum phase diagrams as the interspecies repulsion is increased.
In particular, we analyze the low-energy quantum emulsion metastable states
occurring at large values of the interspecies interaction, which are expected
to prevent the system from reaching its true ground state. A significant
decrease in the visibility of the atomic clouds is predicted as well, and
related to the trapping of the system in the spontaneously disordered quantum
emulsion states.
\\ ( , 43kb)
Date: Tue, 29 Jul 2008 00:43:32 GMT (781kb)

Title: Three-body Interactions in one Dimension
Authors: B. Capogrosso-Sansone, S. Wessel, H.P. B\u"chler, P. Zoller, and G.
Categories: cond-mat.other
Comments: 4 pages, 4 figures
   We determine the phase-diagram of an ensemble of hard-core lattice bosons
interacting via repulsive three-body interactions in one dimension by analytic
methods and extensive quantum Monte-Carlo simulations. Such three-body
interactions can be derived from a microscopic theory for polar molecules
trapped in an optical lattice. Depending on the strength of the interactions
and the particle density, we find superfluid and solid phases, the latter
appearing at an unconventional filling of the lattice and displaying a novel
coexistence of charge-density-wave and bond orders.
\\ ( , 781kb)
Date: Tue, 29 Jul 2008 10:41:00 GMT (9kb)

Title: The absence of fragmentation in Bose-Einstein condensates
Authors: A. D. Jackson, G. M. Kavoulakis, M. Magiropoulos
Categories: cond-mat.other
Comments: 4 pages
   A Bose-Einstein condensate produced by a Hamiltonian which is rotationally or
translationally symmetric is fragmented as a direct result of these symmetries.
A corresponding mean-field unfragmented state, with an identical energy to
leading order in the number of particles, can generally be constructed. As a
consequence, vanishingly weak symmetry-breaking perturbations destabilize the
fragmented state, which would thus be extremely difficult to realize
experimentally, and lead to an unfragmented condensate.
\\ ( , 9kb)
Date: Tue, 29 Jul 2008 18:47:48 GMT (138kb)

Title: Quantum Thermodynamics of Non-Ideal Gases
Authors: Antonin Coutant and S. G. Rajeev
Categories: cond-mat.stat-mech
   We show that when the thermal wavelength is comparable to the spatial size of
a system, thermodynamic observables like Pressure and Volume have quantum
fluctuations that cannot be ignored. They are now represented by operators;
conventional (classical) thermodynamics is no longer applicable. We continue
the work in earlier papers where quantization rules for thermodynamics were
developed by analogy with optics and mechanics, by working out explicitly the
quantum theory of van der Waals gases. We find a wave equation satisfied by the
thermodynamic wave function as well as solutions ({\em coherent states}) that
are centered at the classical equations of state. The probability of departure
from the classical theory is dependent on a parameter $\sigma$ which is a
property of the gas molecule.
\\ ( , 138kb)
Date: Tue, 29 Jul 2008 19:52:12 GMT (1480kb)

Title: On the dark nature of exciton Bose-Einstein condensate
Authors: Monique Combescot, Michael N. Leuenberger
Categories: cond-mat.str-el
Comments: 6 pages, 6 figures
   We show that for the very same reason that excitons are bright, i.e. coupled
to photons, they have a higher energy than dark excitons, even for electrons
spatially separated from holes, such as in a double quantum well. Indeed, the
same channel which produces the finite electron-hole effective overlap
responsible for the absorption and emission of photon allows for Coulomb
interband exchange processes, which are nothing but a sequence of virtual
recombination and creation of one electron-hole pair. Consequently, this
additional repulsive electron-hole Coulomb exchange interaction exists for
bright excitons, but not for dark excitons. If we now remember that dark
excitons with spins $\pm 2$ are formed in a natural way through carrier
exchange between two opposite spin bright excitons, we are led to predict that
in a double quantum well sample with one trap -- a configuration appropriate to
get high density -- exciton Bose-Einstein condensation should appear when
cooling down the sample as a dark spot made of $(\pm 2)$ excitons at the center
of the trap.
\\ ( , 1480kb)
arXiv:0807.4440 (*cross-listing*)
Date: Mon, 28 Jul 2008 13:09:45 GMT (330kb)

Title: Unusual decoherence in qubit measurements with a Bose-Einstein
Authors: D. Sokolovski and S.A. Gurvitz
Categories: quant-ph cond-mat.mes-hall
Comments: 4 pages
   We consider an electrostatic qubit located near a Bose-Einstein condensate
(BEC) of noninteracting bosons in a double-well potential, which is used for
qubit measurements. Tracing out the BEC variables we obtain a simple analytical
expression for the qubit's density-matrix. The qubit's evolution exhibits a
slow ($\propto1/\sqrt{t}$) damping of the qubit's coherence term, in contrast
to the exponential damping produced by most classical detectors. The
decoherence is, in general, incomplete and strongly depends on the initial
state of the qubit. In the special case of a static qubit the suppression of
the coherence term is shown to be Gaussian in time.
\\ ( , 330kb)
Date: Wed, 30 Jul 2008 08:50:46 GMT (84kb)

Title: Towards Landau parameters of strongly interacting fermions with a
   nonlinear transformation
Authors: Ji-sheng Chen
Categories: cond-mat.stat-mech
Comments: 4 pages, 2 figures
   A nonlinear transformation approach is formulated for the correlated fermions
thermodynamics through a medium dependent potential. With an auxiliary implicit
variable-effective chemical potential, the grand partition function is made of
coupled parametric equations. With the Sommerfeld lemma, the low temperature
expansions are performed for the adiabatic compressibility (sound speed) and
specific heat. The expressions for the Landau parameters $F_0^s$ and $F_1^s$
are obtained. As an universal constant, the effective fermion mass is
$m^*={10/9}m$. The study shows that there is a knee peak at $T^*\approx 0.21
T_f$ for the ratio of specific heat at unitarity to that of ideal Fermi gas.
This unusual behavior results from the competitive particle number density and
temperature fluctuations.
\\ ( , 84kb)
Date: Wed, 30 Jul 2008 18:31:34 GMT (185kb)

Title: Vortex Molecules in Spinor Condensates
Authors: Ari M. Turner and Eugene Demler
Categories: cond-mat.supr-con cond-mat.other
Comments: 28 pages, 12 figures
   Condensates of atoms with spins can have vortices of several types; these are
related to the symmetry group of the atoms' ground state. We discuss how, when
a condensate is placed in a small magnetic field that breaks the spin symmetry,
these vortices may form bound states. Using symmetry classification of
vortex-charge and rough estimates for vortex interactions, one can show that
some configurations that are stable at zero temperature can decay at finite
temperatures by crossing over energy barriers. Our focus is cyclic spin 2
condensates, which have tetrahedral symmetry.
\\ ( , 185kb)
Date: Tue, 29 Jul 2008 23:51:13 GMT (393kb)

Title: Backaction noise produced via cavity-aided nondemolition measurement of
   an atomic clock state
Authors: Igor Teper, Geert Vrijsen, Jongmin Lee, and Mark A. Kasevich
Categories: quant-ph
Comments: 4.1 pages, 3 figures
   We use a quantum nondemolition measurement to probe the collective pseudospin
of an atomic ensemble in a high-finesse optical cavity. We analyze the
backaction antisqueezing produced by the measurement process to show that our
protocol can create conditional spin squeezing in the atomic ensemble.
\\ ( , 393kb)
Date: Thu, 31 Jul 2008 05:00:26 GMT (71kb)

Title: Dynamical pattern formation during growth of a dual-species
   Bose-Einstein condensate
Authors: Shai Ronen, John L. Bohn, Laura E. Halmo, and Mark Edwards
Categories: cond-mat.other
   We simulate the growth of a dual species Bose-Einstein condensate using a
Gross-Pitaevskii equation with an additional gain term giving rise to the
growth. Such growth occurs during simultaneous evaporative cooling of a mixture
of two gases. The ground state of a dual condensate is normally either a
miscible mixture, or an immiscible phase with two spatially separated
components. In a cigar trap the ground state typically consists of one
component in the center, and the other component flanking it. Our simulations
show that when the condensates are formed in a cigar trap and the mixture is
phase separated, then the final state upon the end of the growth is generally
far from the true ground state of the system. Instead it consists of multiple,
interleaved bubbles of the two species. Such a pattern was observed recently in
an experiment by Wieman's group at JILA, and our simulations are in good
qualitative agreement with the experiment. We explain the pattern formation as
due to the onset of modulation instability during growth, and study the
dependence of the final state pattern on various parameters of the system.
\\ ( , 71kb)
Date: Thu, 31 Jul 2008 06:27:41 GMT (103kb)

Title: Imbalanced superfluid state in an annular disk
Authors: Fei Ye, Yan Chen, Z. D. Wang and F. C. Zhang
Categories: cond-mat.supr-con
Comments: 8 pages, 10 figures
   The imbalanced superfluid state with an s-wave pairing of spin-1/2 fermions
in an annular disk is numerically studied by solving the Bogoliubov-de-Gennes
equation at zero temperature. Annular disks with narrow radial width and the
one-dimensional ring are considered, where the superfluid order parameter
modulates only along the circumferential direction. The calculations are
carried out for two distinct types of systems. The first case may be relevant
to heavy fermion superconductors, where the electrons spins interact with an
external magnetic field via the Zeeman term and the system is studied in a
grand canonical ensemble. The second case may be relevant to cold fermion
atoms, where the number of fermions of each spin is fixed, and the system is
studied in a canonical ensemble. In the first case, as the magnetic field
increases, the system is transformed from a uniform superfluid state to the
Fulde-Ferrel-Larkin-Ovchinnikov state with sinusoidally modulated pairing order
parameter, and then to a spin polarized normal state. In the second case, the
ground state of the spin imbalanced system depends on the pairing strength. For
weak pairing interactions, the ground state exhibits a periodic domain wall
lattice pattern with a localized spin distribution for low spin imbalance, and
a sinusoidally modulated pattern with extended spin distribution for high spin
imbalance. For strong pairing interactions, the phase separation between
superfluid state and polarized normal state is found to be more preferable,
while the increase of spin imbalance simply extends the spatial region of the
normal state. The condition for the occurrence of Sarma state is also discussed
in this ring disk geometry.
\\ ( , 103kb)
Date: Thu, 31 Jul 2008 08:03:45 GMT (14kb)

Title: Asymptotic localization of stationary states in the nonlinear
   Schroedinger equation
Authors: Shmuel Fishman, Alexander Iomin, and Kirone Mallick
Categories: cond-mat.stat-mech
   The mapping of the Nonlinear Schroedinger Equation with a random potential on
the Fokker-Planck equation is used to calculate the localization length of its
stationary states. The asymptotic growth rates of the moments of the wave
function and its derivative for the linear Schroedinger Equation in a random
potential are computed analytically and resummation is used to obtain the
corresponding growth rate for the nonlinear Schroedinger equation and the
localization length of the stationary states.
\\ ( , 14kb)
Date: Thu, 31 Jul 2008 13:46:29 GMT (51kb)

Title: Atom-atom correlations from condensate collisions
Authors: Magnus Ogren and K. V. Kheruntsyan
Categories: cond-mat.other cond-mat.stat-mech
Comments: 4 pages, 1 figure
   We analyze atom-atom correlations in the s-wave scattering halo of two
colliding condensates. By developing a simple perturbative approach we obtain
explicit analytic results for the collinear (CL) and back-to-back (BB)
correlations corresponding to realistic density profiles of the colliding
condensates with interactions. The results in the short time limit are in
agreement with the first-principles simulations using the positive-P
representation and provide analytic insights to the experimental observations
of Perrin et al., Phys. Rev. Lett. 99, 150405 (2007). For long collision
durations, we predict that the BB correlation becomes broader than the CL
\\ ( , 51kb)
Date: Thu, 31 Jul 2008 16:43:56 GMT (17kb)

Title: Thomas-Fermi versus one- and two-dimensional regimes of a trapped
   dipolar Bose-Einstein condensate
Authors: N.G. Parker and D.H.J. O'Dell
Categories: cond-mat.other
Comments: 5 pages, 2 figures
   We derive the criteria for the Thomas-Fermi regime of a dipolar Bose-Einstein
condensate in cigar, pancake and spherical geometries. This also naturally
gives the criteria for the mean-field one- and two-dimensional regimes. Our
predictions, including the Thomas-Fermi density profiles, are shown to be in
excellent agreement with numerical solutions. Importantly, the anisotropy of
the interactions has a profound effect on the Thomas-Fermi/low-dimensional
\\ ( , 17kb)
Date: Thu, 31 Jul 2008 13:47:29 GMT (280kb)

Title: A millisecond quantum memory for scalable quantum networks
Authors: Bo Zhao, Yu-Ao Chen, Xiao-Hui Bao, Thorsten Strassel, Chih-Sung Chuu,
   Xian-Min Jin, J\"org Schmiedmayer, Zhen-Sheng Yuan, Shuai Chen, Jian-Wei Pan
Categories: quant-ph
Comments: 11pages, 4 figures, submitted for publication
   Scalable quantum information processing critically depends on the capability
of storage of a quantum state. In particular, a long-lived storable and
retrievable quantum memory for single excitations is of crucial importance to
the atomic-ensemble-based long-distance quantum communication. Although atomic
memories for classical lights and continuous variables have been demonstrated
with milliseconds storage time, there is no equal advance in the development of
quantum memory for single excitations, where only around 10 $\mu$s storage time
was achieved. Here we report our experimental investigations on extending the
storage time of quantum memory for single excitations. We isolate and identify
distinct mechanisms for the decoherence of spin wave (SW) in atomic ensemble
quantum memories. By exploiting the magnetic field insensitive state, ``clock
state", and generating a long-wavelength SW to suppress the dephasing, we
succeed in extending the storage time of the quantum memory to 1 ms. Our result
represents a substantial progress towards long-distance quantum communication
and enables a realistic avenue for large-scale quantum information processing.
\\ ( , 280kb)

The replacements:

replaced with revised version Thu, 24 Jul 2008 22:34:25 GMT (1263kb)

Title: One-dimensional extended Hubbard model in the atomic limit
Authors: F. Mancini and F. P. Mancini
Categories: cond-mat.str-el cond-mat.stat-mech
Comments: 28 pages;added references and corrected typos. This paper is an
   extended version of Phys. Rev. E 77, 061120 (2008)
Journal-ref: Phys. Rev. E 77, 061120 (2008)
DOI: 10.1103/PhysRevE.77.061120
\\ ( , 1263kb)
replaced with revised version Mon, 28 Jul 2008 15:47:30 GMT (203kb)

Title: Berry Phase Effect on Exciton Transport and Bose Einstein Condensate
Authors: Wang Yao, Qian Niu
Categories: cond-mat.mes-hall
Comments: to appear in Phys. Rev. Lett
\\ ( , 203kb)
arXiv:0803.1280 (*cross-listing*)
replaced with revised version Mon, 28 Jul 2008 17:37:50 GMT (726kb)

Title: The ground state energy at unitarity
Authors: Dean Lee (North Carolina State University)
Categories: nucl-th cond-mat.other hep-lat
Comments: 31 pages, 10 figures, version to appear in Phys. Rev. C
\\ ( , 726kb)
replaced with revised version Mon, 28 Jul 2008 20:42:06 GMT (1001kb,D)

Title: Symmetry-conserving vortex clusters in small rotating clouds of
   ultracold bosons
Authors: Igor Romanovsky, Constantine Yannouleas, Uzi Landman
Categories: cond-mat.mes-hall cond-mat.other nucl-th physics.atm-clus
Comments: Revtex 4 with 4 color figures. Published version. Ref. [25]
   (experimental) was added. For related papers, see
Journal-ref: Phys. Rev. A 78, 011606(R) (2008)
DOI: 10.1103/PhysRevA.78.011606
\\ ( , 1001kb)
replaced with revised version Wed, 30 Jul 2008 17:26:57 GMT (142kb)

Title: Temperature and final state effects in radio frequency spectroscopy
   experiments on atomic Fermi gases
Authors: Yan He, Chih-Chun Chien, Qijin Chen, and K. Levin
Categories: cond-mat.supr-con cond-mat.str-el
Comments: 4 pages, 4 figures
\\ ( , 142kb)
replaced with revised version Wed, 30 Jul 2008 20:38:59 GMT (73kb)

Title: Quantum Monte Carlo study of the visibility of one-dimensional
   Bose-Fermi mixtures
Authors: C. N. Varney, V. G. Rousseau, R. T. Scalettar
Categories: cond-mat.other
Comments: 4 pages, 6 figures
Journal-ref: Phys. Rev. A 77, 041608(R) (2008)
DOI: 10.1103/PhysRevA.77.041608
\\ ( , 73kb)

Till next time,

Dr M. J. Davis,               Senior Lecturer in Physics
School of Physical Sciences,  email:
University of Queensland,     ph   : +61 7 334 69824
Brisbane, QLD 4072,           fax  : +61 7 336 51242
Matt's arXiv selection: weekly summary of cold-atom papers from
Legal stuff: Unless stated otherwise, this e-mail represents only the
views of the sender and not the views of the University of Queensland
Received on Tue Aug 26 2008 - 09:40:05 EST

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