Matt's arXiv selection: week ending 25 July 2008

From: Matthew Davis <>
Date: Wed, 06 Aug 2008 11:47:50 +1000

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

Hi everyone,

I've been sitting here waiting for a plane for the last hour and a half, and
I've managed to collate the next installment. There were 35 new preprints and
17 replacements this week.

Date: Thu, 17 Jul 2008 21:34:35 GMT (470kb)

Title: Nonlinear response of the vacuum Rabi resonance
Authors: Lev S. Bishop, J. M. Chow, Jens Koch, A. A. Houck, M. H. Devoret, E.
   Thuneberg, S. M. Girvin, R. J. Schoelkopf
Categories: cond-mat.mes-hall cond-mat.supr-con
Comments: 6 pages, 4 figures. Supplementary Material and Supplementary Movies
   are available at
   On the level of single atoms and photons, the coupling between atoms and the
electromagnetic field is typically very weak. By employing a cavity to confine
the field, the strength of this interaction can be increased many orders of
magnitude to a point where it dominates over any dissipative process. This
strong-coupling regime of cavity quantum electrodynamics has been reached for
real atoms in optical cavities, and for artificial atoms in circuit QED and
quantum-dot systems. A signature of strong coupling is the splitting of the
cavity transmission peak into a pair of resolvable peaks when a single resonant
atom is placed inside the cavity - an effect known as vacuum Rabi splitting.
The circuit QED architecture is ideally suited for going beyond this linear
response effect. Here, we show that increasing the drive power results in two
unique nonlinear features in the transmitted heterodyne signal: the
supersplitting of each vacuum Rabi peak into a doublet, and the appearance of
additional peaks with the characteristic sqrt(n) spacing of the Jaynes-Cummings
ladder. These constitute direct evidence for the coupling between the quantized
microwave field and the anharmonic spectrum of a superconducting qubit acting
as an artificial atom.
\\ ( , 470kb)
Date: Fri, 18 Jul 2008 03:57:23 GMT (162kb)

Title: Heavily Damped Motion of One-Dimensional Bose Gases in an Optical
Authors: Ippei Danshita, Charles W. Clark
Categories: cond-mat.other
Comments: 4 pages, 5 figures
   We study the dynamics of strongly correlated one-dimensional Bose gases in a
combined harmonic and optical lattice potential subjected to sudden
displacement of the confining potential. Using the time-evolving block
decimation method, we perform a first-principles quantum many-body simulation
of the experiment of Fertig {\it et al.} [Phys. Rev. Lett. {\bf 94}, 120403
(2005)] - the first, to our knowledge, to incorporate all details of the
experimental parameters. We find good quantitative agreement with this
experiment: the damping of the dipole oscillations is significant even for
shallow lattices, and the motion becomes overdamped with increasing lattice
depth as observed. We show that the transition to overdamping is attributed to
the decay of superfluid flow accelerated by quantum fluctuations, which occurs
well before the emergence of Mott insulator domains.
\\ ( , 162kb)
Date: Fri, 18 Jul 2008 10:00:11 GMT (176kb)

Title: Gapless superfluidity in the attractive Hubbard model with population
Authors: Tung-Lam Dao, Michel Ferrero, Antoine Georges, Massimo Capone, Olivier
Categories: cond-mat.supr-con cond-mat.str-el
Comments: 4+ pages, 4 figures
   We study a two-component Fermi system with attractive interactions and
different populations of the two species in a three-dimensional cubic lattice.
For an intermediate coupling in the Bose-Einstein condensation (BEC) regime, we
find a uniformly polarized gapless superfluid (breached-pair phase) which is
stable down to very low temperatures. The condensation energy of this phase
corresponds to a stabilization by potential energy, as in a BCS superfluid, in
contrast to the unpolarized BEC which is stabilized by kinetic energy. We
present general arguments suggesting that preformed pairs in the unpolarized
superfluid favor the stabilization of a breached-pair phase.
\\ ( , 176kb)
Date: Fri, 18 Jul 2008 12:14:49 GMT (2755kb)

Title: Long-range correlations of density in a Bose-Einstein condensate
   expanding in a random potential
Authors: N. Cherroret, S. E. Skipetrov
Categories: cond-mat.dis-nn cond-mat.mes-hall
Comments: 4 pages, 5 figures
   We study correlations of atomic density in a weakly interacting Bose-Einstein
condensate, expanding diffusively in a random potential. We show that these
correlations are long-range and that they are strongly enhanced at long times.
Density at distant points exhibits negative correlations.
\\ ( , 2755kb)
Date: Fri, 18 Jul 2008 14:31:04 GMT (59kb)

Title: The two-body problem of ultra-cold atoms in a harmonic trap
Authors: Patrick Shea, Brandon P. van Zyl, Rajat K. Bhaduri
Categories: physics.atom-ph cond-mat.other
   In this pedagogical article, we consider two bosonic atoms interacting with a
short range potential, and trapped in a spherically symmetric harmonic
oscillator. The problem is exactly solvable, and is relevant in the research of
ultra-cold atoms. We show that the energy spectrum is universal, irrespective
of the shape of the interaction potential, provided its range is much smaller
than the oscillator length.
\\ ( , 59kb)
Date: Fri, 18 Jul 2008 17:48:22 GMT (330kb)

Title: Sum-frequency generation of 589 nm light with near-unit efficiency
Authors: Emmanuel Mimoun, Luigi De Sarlo, Jean-Jacques Zondy, Jean Dalibard,
   and Fabrice Gerbier
Categories: physics.optics
   We report on a laser source at 589 nm based on sum-frequency generation of
two infrared laser at 1064 nm and 1319 nm. Output power as high as 800 mW are
achieved starting from 370 mW at 1319 nm and 770 mW at 1064 nm, corresponding
to converting roughly 90% of the 1319 nm photons entering the cavity.
\\ ( , 330kb)
Date: Sun, 20 Jul 2008 16:00:27 GMT (520kb,D)

Title: Ultracold atom spin field effect transistors
Authors: J. Y. Vaishnav, Julius Ruseckas, Charles W. Clark, Gediminas
Categories: cond-mat.mes-hall cond-mat.other
   We propose a method of constructing cold atom analogs of the spintronic
device known as the Datta-Das transistor (DDT), which despite its seminal
conceptual role in spintronics, has never been successfully realized with
electrons. We propose two alternative schemes for an atomic DDT, both of which
are based on the experimental setup for tripod stimulated Raman adiabatic
passage. Both setups involve atomic beams incident on a series of laser fields
mimicking the relativistic spin orbit coupling for electrons that is the
operating mechanism of the DDT.
\\ ( , 520kb)
Date: Sun, 20 Jul 2008 01:38:36 GMT (922kb)

Title: Bose-Einstein condensates of polar molecules: anisotropic interactions =
   anisotropic mass
Authors: Andrei Derevianko
Categories: cond-mat.other
   So far the theory of Bose-Einstein condensates (BEC) of polar molecules was
based on an ad hoc generalization of equations for spherical atoms. Here I
adopt a rigorous pseudo-potential approach to low-energy dipolar interactions
and derive a non-linear mean-field Schrodinger equation for a
harmonically-trapped condensate. I show that, effectively, the dipolar
interactions alter molecular mass. The resulting effective mass is anisotropic:
to the leading order the mass is altered only for the motion along the
polarizing field. For a typical BEC of spin-polarized magnetically-interacting
alkali-metal atoms the effective atomic mass is reduced by 10% from its bare
value. For a BEC of polar molecules the mass may be reduced by a factor of a
\\ ( , 922kb)
Date: Sun, 20 Jul 2008 18:57:05 GMT (42kb)

Title: Mesoscopic Aspects of Strongly Interacting Cold Atoms
Authors: S.D. Huber, G. Blatter
Categories: cond-mat.other cond-mat.str-el cond-mat.supr-con
Comments: 5 pages, 1 figure
   Harmonically trapped lattice bosons with strong repulsive interactions
exhibit a superfluid-Mott insulator heterostructure in the form of a ''wedding
cake''. We discuss the mesoscopic nature of such a system within a
one-dimensional model and calculate the scattering properties of
quasi-particles at a superfluid--Mott-insulator interface as an elementary
building block to describe transport phenomena across such a boundary.
\\ ( , 42kb)
Date: Mon, 21 Jul 2008 19:21:19 GMT (141kb)

Title: Observation of an Efimov-like resonance in ultracold atom-dimer
Authors: S. Knoop, F. Ferlaino, M. Mark, M. Berninger, H. Schoebel, H.-C.
   Naegerl, R. Grimm
Categories: cond-mat.other
Comments: 12 pages, 3 figures
   The field of few-body physics has originally been motivated by understanding
nuclear matter. New model systems to experimentally explore few-body quantum
systems can now be realized in ultracold gases with tunable interactions.
Albeit the vastly different energy regimes of ultracold and nuclear matter (peV
as compared to MeV), few-body phenomena are universal for near-resonant
two-body interactions. Efimov states represent a paradigm for universal
three-body states, and evidence for their existence has been obtained in
measurements of three-body recombination in an ultracold gas of caesium atoms.
Interacting samples of halo dimers can provide further information on universal
few-body phenomena. Here we study interactions in an optically trapped mixture
of such halo dimers with atoms, realized in a caesium gas at nanokelvin
temperatures. We observe an atom-dimer scattering resonance, which we interpret
as being due to a trimer state hitting the atom-dimer threshold. We discuss the
close relation of this observation to Efimov's scenario, and in particular to
atom-dimer Efimov resonances.
\\ ( , 141kb)
Date: Mon, 21 Jul 2008 18:55:37 GMT (832kb)

Title: Spontaneous vortices in the formation of Bose-Einstein condensates
Authors: C. N. Weiler, T. W. Neely, D. R. Scherer, A. S. Bradley, M. J. Davis,
   B. P. Anderson
Categories: cond-mat.other
Comments: 14 pages, 6 figures. Accepted for publication in Nature.
   Supplementary movie files are available at
   Phase transitions are ubiquitous in nature, ranging from protein folding and
denaturisation, to the superconductor-insulator quantum phase transition, to
the decoupling of forces in the early universe. Remarkably, phase transitions
can be arranged into universality classes, where systems having unrelated
microscopic physics exhibit identical scaling behaviour near the critical
point. Here we present an experimental and theoretical study of the
Bose-Einstein condensation phase transition of an atomic gas, focusing on one
prominent universal element of phase transition dynamics: the spontaneous
formation of topological defects during a quench through the transition. While
the microscopic dynamics of defect formation in phase transitions are generally
difficult to investigate, particularly for superfluid phase transitions,
Bose-Einstein condensates (BECs) offer unique experimental and theoretical
opportunities for probing such details. Although spontaneously formed vortices
in the condensation transition have been previously predicted to occur, our
results encompass the first experimental observations and statistical
characterisation of spontaneous vortex formation in the condensation
transition. Using microscopic theories that incorporate atomic interactions and
quantum and thermal fluctuations of a finite-temperature Bose gas, we simulate
condensation and observe vortex formation in close quantitative agreement with
our experimental results. Our studies provide further understanding of the
development of coherence in superfluids, and may allow for direct investigation
of universal phase-transition dynamics.
\\ ( , 832kb)
Date: Sat, 19 Jul 2008 17:20:01 GMT (1598kb)

Title: Ramsey-like measurement of the decoherence rate between Zeeman
Authors: M. Shuker, O. Firstenberg, Y. Sagi, A. Ben-kish, N. Davidson, A. Ron
Categories: quant-ph
Comments: 7 pages, 7 figures
   Two-photon processes that involve different sub-levels of the ground state of
an atom, are highly sensitive to depopulation and decoherence within the ground
state. For example, the spectral width of electromagnetically induced
transparency resonances in $\Lambda-$type system, are strongly affected by the
ground state depopulation and decoherence rates. We present a direct
measurement of decay rates between hyperfine and Zeeman sub-levels in the
ground state of $^{87}$Rb vapor. Similar to the relaxation-in-the-dark
technique, pumping lasers are used to pre-align the atomic vapor in a well
defined quantum state. The free propagation of the atomic state is monitored
using a Ramsey-like method. Coherence times in the range 1-10 ms were measured
for room temperature atomic vapor. In the range of the experimental parameters
used in this study, the dominant process inducing Zeeman decoherence is the
spin-exchange collisions between rubidium atoms.
\\ ( , 1598kb)
Date: Mon, 21 Jul 2008 14:17:59 GMT (295kb)

Title: Formation of ultracold polar molecules in the rovibrational ground state
Authors: J. Deiglmayr, A. Grochola, M. Repp, K. M\"ortlbauer, C. Gl\"uck, J.
   Lange, O. Dulieu, R. Wester, and M. Weidem\"uller
Categories: quant-ph
   Ultracold LiCs molecules in the absolute ground state X$^1\Sigma^+$, v"=0,
J"=0 are formed via a single photo-association step starting from laser-cooled
atoms. The selective production of v"=0, J"=2 molecules with a 50-fold higher
rate is also demonstrated. The rotational and vibrational state of the ground
state molecules is determined in a setup combining depletion spectroscopy with
resonant-enhanced multi-photon ionization time-of-flight spectroscopy. Using
the determined production rate of up to 5x10^3 molecules/s, we describe a
simple scheme which can provide large samples of externally and internally cold
dipolar molecules.
\\ ( , 295kb)
Date: Mon, 21 Jul 2008 16:31:19 GMT (125kb)

Title: Calculations of static dipole polarizabilities of alkali dimers.
   Prospects for alignment of ultracold molecules
Authors: Johannes Deiglmayr, Mireille Aymar, Roland Wester, Matthias
   Weidem\"uller, Olivier Dulieu
Categories: physics.atom-ph
Comments: Accepted for publication in J Chem Phys
   The rapid development of experimental techniques to produce ultracold alkali
molecules opens the ways to manipulate them and to control their dynamics using
external electric fields. A prerequisite quantity for such studies is the
knowledge of their static dipole polarizabilities. In this paper, we computed
the variations with internuclear distance and with vibrational index of the
static dipole polarizability components of all homonuclear alkali dimers
including Fr$_2$, and of all heteronuclear alkali dimers involving Li to Cs, in
their electronic ground state and in their lowest triplet state. We use the
same quantum chemistry approach than in our work on dipole moments (M. Aymar
and O. Dulieu, J. Chem. Phys. 122, 204302 (2005)), based on pseudopotentials
for atomic core representation, Gaussian basis sets, and effective potentials
for core polarization. Polarizabilities are extracted from electronic energies
using the finite-field method. For the heaviest species Rb$_2$, Cs$_2$ and
Fr$_2$ and for all heteronuclear alkali dimers, such results are presented for
the first time. The accuracy of our results on atomic and molecular static
dipole polarizabilities is discussed by comparing our values with the few
available experimental data and elaborate calculations. We found that for all
alkali pairs, the parallel and perpendicular components of the ground state
polarizabilities at the equilibrium distance $R_e$ scale as $(R_e)^3$, which
can be related to a simple electrostatic model of an ellipsoidal charge
distribution. Prospects for possible alignment and orientation effects with
these molecules in forthcoming experiments are discussed.
\\ ( , 125kb)
Date: Mon, 21 Jul 2008 12:41:59 GMT (141kb,D)

Title: The Emperor's Last Clothes?
Authors: A.N. Schellekens
Categories: physics.pop-ph
Comments: 87 pages, Review intended for readers with an education in physics
   We are in the middle of a remarkable paradigm shift in particle physics, a
shift of opinion that occurred so slowly that some even try to deny that they
changed their minds at all. It concerns a very basic question: can we expect to
derive the laws of particle physics from a fundamental theory? The Standard
Model of particle physics as well as the 1984 string theory revolution provided
ample food for thought about this. The reason this was ignored for so long can
be traced back to an old fallacy: a misguided idea about our own importance.
\\ ( , 141kb)
Date: Mon, 21 Jul 2008 22:05:02 GMT (30kb)

Title: Motion of an impurity particle in an ultracold quasi-one-dimensional gas
   of hard-core bosons
Authors: M.D. Girardeau and A. Minguzzi
Categories: cond-mat.other
Comments: 4 pages, 2 figures, revtex4. Submitted to PRL
   The low-lying eigenstates of a one-dimensional (1D) system of many
impenetrable point bosons and one moving impurity particle with repulsive
zero-range impurity-boson interaction are found exactly for all values of the
impurity-boson mass ratio and coupling constant. The moving entity is a
polaron-like composite object consisting of the impurity clothed by a co-moving
gray soliton. The special case with impurity-boson interaction of point
hard-core form and impurity-boson mass ratio $m_i/m$ unity is first solved
exactly as a special case of a previous Fermi-Bose (FB) mapping treatment of
soluble 1D Bose-Fermi mixture problems. Then a more general treatment is given
using second quantization for the bosons and the second-quantized form of the
FB mapping, eliminating the impurity degrees of freedom by a Lee-Low-Pines
canonical transformation. This yields the exact solution for arbitrary $m_i/m$
and impurity-boson interaction strength. A stability breakdown occurs when the
impurity velocity reaches the speed of sound, associated with acoustical
Cerenkov radiation (Mach waves).
\\ ( , 30kb)
Date: Tue, 22 Jul 2008 09:33:54 GMT (190kb)

Title: Dynamics of kicked matter-wave solitons in an optical lattice
Authors: A. Cetoli, L. Salasnich, B.A. Malomed, F. Toigo
Categories: cond-mat.other
Comments: 8 pages, 6 figures, to be published in Physica D: Nonlinear
   Phenomena; special issue on "Nonlinear Phenomena in Degenerate Quantum Gases"
   We investigate effects of the application of a kick to one-dimensional
matter-wave solitons in a self-attractive Bose-Einstein condensate trapped in a
optical lattice. The resulting soliton's dynamics is studied within the
framework of the time-dependent nonpolynomial Schrodinger equation. The
crossover from the pinning to quasi-free motion crucially depends on the size
of the kick, strength of the self-attraction, and parameters of the optical
\\ ( , 190kb)
Date: Tue, 22 Jul 2008 09:48:41 GMT (140kb)

Title: Pair correlations of scattered atoms from two colliding Bose-Einstein
   Condensates: Perturbative Approach
Authors: J. Chwedenczuk, P. Zin, M. Trippenbach, A. Perrin, V. Leung, D. Boiron
   and C. I. Westbrook
Categories: cond-mat.other
Comments: 9 pages, 3 figures
   We apply an analytical model for anisotropic, colliding Bose-Einstein
condensates in a spontaneous four wave mixing geometry to evaluate the second
order correlation function of the field of scattered atoms. Our approach uses
quantized scattering modes and the equivalent of a classical, undepleted pump
approximation. Results to lowest order in perturbation theory are compared with
a recent experiment and with other theoretical approaches.
\\ ( , 140kb)
Date: Tue, 22 Jul 2008 10:24:20 GMT (26kb)

Title: A Fortran 90 program to solve the Hartree-Fock equations for interacting
   spin-1/2 Fermions confined in Harmonic potentials
Authors: H. K. Pal and A. Shukla
Categories: cond-mat.other
Comments: 19 pages and 2 figures
Journal-ref: Comp. Phys. Communications 179, 267 (2008)
   A set of weakly interacting spin-1/2 Fermions, confined by a harmonic
oscillator potential, and interacting with each other via a contact potential,
is a model system which closely represents the physics of a dilute gas of
two-component Fermionic atoms confined in a magneto-optic trap. In the present
work, our aim is to present a Fortran 90 computer program which, using a basis
set expansion technique, solves the Hartree-Fock (HF) equations for spin-1/2$
Fermions confined by a three-dimensional harmonic oscillator potential, and
interacting with each other via pair-wise delta-function potentials.
Additionally, the program can also account for those anharmonic potentials
which can be expressed as a polynomial in the position operators $x,$ $y$, and
$z$. Both the restricted-HF (RHF), and the unrestricted-HF (UHF) equations can
be solved for a given number of Fermions, with either repulsive or attractive
interactions among them. The option of UHF solutions for such systems also
allows us to study possible magnetic properties of the physics of two-component
confined atomic Fermi gases, with imbalanced populations. Using our code we
also demonstrate that such a system exhibits shell structure, and follows
Hund's rule.
\\ ( , 26kb)
Date: Tue, 22 Jul 2008 14:59:34 GMT (300kb)

Title: Gap solitons in a model of a superfluid fermion gas in optical lattices
Authors: S. K. Adhikari and B. A. Malomed
Categories: cond-mat.other
   We consider a dynamical model for a Fermi gas in the
Bardeen-Cooper-Schrieffer (BCS) superfluid state, trapped in a combination of a
1D or 2D optical lattice (OL) and a tight parabolic potential acting in the
transverse direction(s). The model is based on an equation for the order
parameter (wave function), which is derived from the energy density for the
weakly coupled BCS superfluid. The equation includes a nonlinear self-repulsive
term of power 7/3, which accounts for the Fermi pressure. Reducing the equation
to the 1D or 2D form, we construct families of stable 1D and 2D gap solitons
(GSs) by means of numerical simulations, which are guided by the variational
approximation (VA). The GSs are, chiefly, compact objects trapped in a single
cell of the OL potential. In the linear limit, the VA predicts almost exact
positions of narrow Bloch bands that separate the semi-infinite and first
finite gaps, as well as the first and second finite ones. Families of stable
even and odd bound states of 1D GSs are constructed too. We also demonstrate
that the GS can be dragged without much distortion by an OL moving at a
moderate velocity ($\sim $ 1 mm/s, in physical units). The predicted GSs
contain $\sim 10^{3}-10^{4}$ and $\sim 10^{3}$ atoms per 1D and 2D settings,
\\ ( , 300kb)
Date: Tue, 22 Jul 2008 16:51:59 GMT (144kb)

Title: Phase Transition in Space: How Far Does a Symmetry Bend Before It
Authors: Wojciech H. Zurek and Uwe Dorner
Categories: cond-mat.stat-mech
Comments: 10 pages, 8 figures. Published online 5 June 2008
Journal-ref: Phil. Trans. R. Soc. A 366, 2953 (2008)
DOI: 10.1098/rsta.2008.0069
   We extend the theory of symmetry breaking dynamics in non-equilibrium second
order phase transitions known as the Kibble-Zurek mechanism (KZM) to
transitions where the change of phase occurs not in time, but in space. This
can be due to a time-independent spatial variation of a field that imposes a
phase with one symmetry to the left of where it attains critical value, while
allowing spontaneous symmetry breaking to the right of that critical
borderline. Topological defects need not form in such a situation. We show,
however, that the size, in space, of the ``scar'' over which the order
parameter adjusts as it ``bends'' interpolating between the phases with
different symmetry follows from a KZM - like approach. As we illustrate on the
example of a transverse quantum Ising model, in quantum phase transitions this
spatial scale -- the size of the scar -- is directly reflected in the energy
spectrum of the system: In particular, it determines the size of the energy
\\ ( , 144kb)
Date: Mon, 21 Jul 2008 21:14:52 GMT (2267kb,D)

Title: Quantum interface between light and atomic ensembles
Authors: K. Hammerer, A.S. Sorensen, E.S. Polzik
Categories: quant-ph
Comments: 52 pages, 22 figures, to appear in Reviews of Modern Physics
   During the past decade the interaction of light with multi-atom ensembles has
attracted a lot of attention as a basic building block for quantum information
processing and quantum state engineering. The field started with the
realization that optically thick free space ensembles can be efficiently
interfaced with quantum optical fields. By now the atomic ensemble - light
interfaces have become a powerful alternative to the cavity-enhanced
interaction of light with single atoms. We discuss various mechanisms used for
the quantum interface, including quantum nondemolition or Faraday interaction,
quantum measurement and feedback, Raman interaction and electromagnetically
induced transparency. The paper provides a common theoretical frame for these
processes, describes basic experimental techniques and media used for quantum
interfaces, and reviews several key experiments on quantum memory for light,
quantum entanglement between atomic ensembles and light, and quantum
teleportation with atomic ensembles. We concentrate on deterministic operations
but also briefly discuss probabilistic protocols. The paper concludes with an
outlook on the future of atomic ensembles as an enabling technology in quantum
information processing.
\\ ( , 2267kb)
Date: Tue, 22 Jul 2008 13:57:16 GMT (729kb)

Title: Bose-Einstein condensation of stationary-light polaritons
Authors: Michael Fleischhauer, Johannes Otterbach, Razmik G. Unanyan
Categories: quant-ph cond-mat.other
Comments: 4 pages, 3 figures
   We propose and analyze a mechanism for Bose-Einstein condensation of
stationary dark-state polaritons. Dark-state polaritons (DSPs) are formed in
the interaction of light with laser-driven 3-level Lambda-type atoms and are
the basis of phenomena such as electromagnetically induced transparency (EIT),
ultra-slow and stored light. They have long intrinsic lifetimes and in a
stationary set-up with two counterpropagating control fields of equal intensity
have a 3D quadratic dispersion profile with variable effective mass. Since DSPs
are bosons they can undergo a Bose-Einstein condensation at a critical
temperature which can be many orders of magnitude larger than that of atoms. We
show that thermalization of polaritons can occur via elastic collisions
mediated by a resonantly enhanced optical Kerr nonlinearity on a time scale
short compared to the decay time. Finally condensation can be observed by
turning stationary into propagating polaritons and monitoring the emitted
\\ ( , 729kb)
Date: Tue, 22 Jul 2008 16:04:30 GMT (1661kb)

Title: Controlling Irreversibility and Directional Flow of Light with Atomic
Authors: C. H. Raymond Ooi
Categories: quant-ph
Comments: 5 pages, 5 figures
   The Doppler effect of moving atoms can create irreversibility of light. We
show that the laser field in electromagnetic induced transparency (EIT) scheme
with atomic motion can control the directional propagation of two
counter-propagating probe fields in atomic gas cell. The quantum coherence
effect serves as an optical transistor. Interference of the two output fields
from the cell shows useful feature for determining the mean atomic velocity and
can be useful as quantum velocimeter. We also find that the sign of the
dispersive phase in EIT has a unique property, which helps to explain certain
features in the interference.
\\ ( , 1661kb)
Date: Tue, 22 Jul 2008 07:32:35 GMT (312kb)

Title: Doppler-free spectroscopy of the 1S0-3P0 optical clock transition in
   laser-cooled fermionic isotopes of neutral mercury
Authors: M. Petersen (SYRTE), R. Chicireanu (SYRTE), S.T. Dawkins (SYRTE), D.V.
   Magalh\~aes (SYRTE, Ifsc-Usp), C. Mandache (SYRTE, Inflpr), Y. Lecoq (SYRTE),
   A. Clairon (SYRTE), S. Bize (SYRTE)
Categories: physics.atom-ph quant-ph
   We have performed for the first time direct laser spectroscopy of the 1S0-3P0
optical clock transition at 265.6 nm in fermionic isotopes of neutral mercury
laser-cooled in a magneto-optical trap. Spectroscopy is performed by measuring
the depletion of the magneto-optical trap induced by the excitation of the
long-lived 3P0 state by a probe at 265.6 nm. Measurements resolve the
Doppler-free recoil doublet allowing for a determination of the transition
frequency to an uncer- tainty well below the Doppler-broadened linewidth. We
have performed absolute measurement of the frequency with respect to an
ultra-stable reference monitored by LNE-SYRTE fountain pri- mary frequency
standards using a femtosecond laser frequency comb. The measured frequency is
1128575290808 +/- 5.6 kHz in 199Hg and 1128569561140 +/- 5.3 kHz in 201Hg, more
than 4 orders of magnitude better than previous indirect determinations. Owing
to a low sensitivity to blackbody radiation, mercury is a promising candidate
for reaching the ultimate performance of optical lattice clocks.
\\ ( , 312kb)
Date: Wed, 23 Jul 2008 06:35:36 GMT (2787kb)

Title: Vortices in rotating optical lattices: commensurability, hysteresis, and
   proximity to the Mott State
Authors: Daniel S. Goldbaum and Erich J. Mueller
Categories: cond-mat.other
Comments: 21 Pages, 6 Figures ; Higher resolution versions of Figs. 1,4,5 are
   available upon request
   Quantized vortices stunningly illustrate the coherent nature of a superfluid
Bose condensate of alkali atoms. Introducing an optical lattice depletes this
coherence. Consequently, novel vortex physics may emerge in an experiment on a
harmonically trapped gas in the presence of a rotating optical lattice. The
most dramatic effects would occur in proximity to the Mott state, an
interaction dominated insulator with a fixed integer number of particles per
site. We model such a rotating gas, showing that the lattice-induced spatial
profile of the superfluid density drives a gross rearrangement of vortices. For
example, instead of the uniform vortex lattices commonly seen in experiments,
we find parameters for which the vortices all sit at a fixed distance from the
center of the trap, forming a ring. Similarly, they can coalesce at the center,
forming a giant vortex. We find that the properties of this system are
hysteretic, even far from the Mott state. We explain this hysteresis in terms
of vortex pinning, commensurability between vortex density and pinning site
density, and energy barriers against changing the number of vortices. Finally,
we model time-of-flight expansion, demonstrating the experimental observability
of our predictions.
\\ ( , 2787kb)
Date: Wed, 23 Jul 2008 09:51:29 GMT (10kb)

Title: Tunneling-induced damping of phase coherence revivals in deep optical
Authors: Uwe R. Fischer and Ralf Sch\"utzhold
Categories: cond-mat.other
Comments: 3.5 pages of RevTex4
   We consider phase coherence collapse and revival in deep optical lattices,
and calculate within the Bose-Hubbard model the revival amplitude damping
incurred by a finite tunneling coupling of the lattice wells (after sweeping
from the superfluid to the Mott phase). Deriving scaling laws for the
corresponding decay of first-order coherence revival in terms of filling
factor, final lattice depth, and number of tunneling coupling partners, we
estimate whether revival-damping related to tunneling between sites can be or
even has already been observed in experiment.
\\ ( , 10kb)
Date: Wed, 23 Jul 2008 10:14:16 GMT (484kb)

Title: Vortex Lattice in a Rotating Bose-Einstein Condensate
Authors: Eniko J. M. Madarassy
Categories: cond-mat.other
Comments: 7 pages, 16 figures
   Numerical simulations of vortex motion in a trapped Bose-Einstein condensate
were performed by solving the two-dimensional Gross-Pitaevskii equation in the
presence of a simple phenomenological model of interaction between the
condensate and the finite temperature thermal cloud. The log (base e) of total
energy, trap energy, quantum energy, kinetic energy, internal energy and
z-component of the angular momentum vs time were compared with f(x)=a+bx for
that time when the vortices come in in the condensate. The increasing/decay
rate of these energies and L_{z} were studied as a function of dissipation.
\\ ( , 484kb)
Date: Wed, 23 Jul 2008 11:10:02 GMT (524kb)

Title: Normal-Superfluid Interface for Polarized Fermion Gases
Authors: Bert Van Schaeybroeck, Achilleas Lazarides
Categories: cond-mat.other cond-mat.stat-mech cond-mat.supr-con
Comments: 11 pages, 5 figures
   Recent experiments on imbalanced fermion gases have proved the existence of a
sharp interface between a superfluid and a normal phase. We show that, at the
lowest experimental temperatures, a temperature difference between N and SF
phase can appear as a consequence of the blocking of energy transfer across the
interface. Such blocking is a consequence of the existence of a SF gap, which
causes low-energy normal particles to be reflected from the N-SF interface. Our
quantitative analysis is based on the Hartree-Fock-Bogoliubov-de Gennes
formalism, which allows us to give analytical expressions for the thermodynamic
properties and characterize the possible interface scattering regimes,
including the case of unequal masses. Our central result is that the thermal
conductivity is exponentially small at the lowest experimental temperatures.
\\ ( , 524kb)
Date: Wed, 23 Jul 2008 14:18:14 GMT (114kb)

Title: Phonon instability in two-dimensional dipolar Bose-Einstein Condensates
Authors: R. Nath, P. Pedri and L. Santos
Categories: cond-mat.other
Comments: 4 pages, 4 figures
   The partially attractive character of the dipole-dipole interaction leads to
phonon instability in dipolar condensates, which is followed by collapse in
three-dimensional geometries. We show that the nature of this instability is
fundamentally different in two-dimensional condensates, due to the
dipole-induced stabilization of two-dimensional bright solitons. As a
consequence, a transient gas of attractive solitons is formed, and collapse may
be avoided. In the presence of an harmonic confinement, the instability leads
to transient pattern formation followed by the creation of stable
two-dimensional solitons. This dynamics should be observable in on-going
experiments, allowing for the creation of stable two-dimensional solitons for
the first time ever in quantum gases.
\\ ( , 114kb)
Date: Wed, 23 Jul 2008 15:30:23 GMT (88kb)

Title: Quantum Diffusion of Matter Waves in 2D Speckle Potentials
Authors: C. Miniatura, R.C. Kuhn, D. Delande, C.A. Mueller
Categories: cond-mat.dis-nn cond-mat.other
Comments: 12 pages
   This paper investigates quantum diffusion of matter waves in two-dimensional
random potentials, focussing on expanding Bose-Einstein condensates in
spatially correlated optical speckle potentials. Special care is taken to
describe the effect of dephasing, finite system size, and an initial momentum
distribution. We derive general expressions for the interference-renormalized
diffusion constant, the disorder-averaged probability density distribution, the
variance of the expanding atomic cloud, and the localized fraction of atoms.
These quantities are studied in detail for the special case of an
inverted-parabola momentum distribution as obtained from an expanding
condensate in the Thomas-Fermi regime. Lastly, we derive quantitative criteria
for the unambiguous observation of localization effects in a possible 2D
\\ ( , 88kb)
Date: Wed, 23 Jul 2008 13:59:16 GMT (501kb)

Title: Light-shift tomography in an optical-dipole trap for neutral atoms
Authors: Jean-Philippe Brantut (LCFIO), Jean-Fran\c{c}ois Cl\'ement (LCFIO),
   Martin Robert De Saint Vincent (LCFIO), Gael Varoquaux (LCFIO), Robert A.
   Nyman (LCFIO), Alain Aspect (LCFIO), Thomas Bourdel (LCFIO), Philippe Bouyer
Categories: physics.atom-ph
   We report on light-shift tomography of a cloud of 87 Rb atoms in a
far-detuned optical-dipole trap at 1565 nm. Our method is based on standard
absorption imaging, but takes advantage of the strong light-shift of the
excited state of the imaging transition, which is due to a quasi-resonance of
the trapping laser with a higher excited level. We use this method to (i) map
the equipotentials of a crossed optical-dipole trap, and (ii) study the
thermalisation of an atomic cloud by following the evolution of the
potential-energy of atoms during the free-evaporation process.
\\ ( , 501kb)
Date: Thu, 24 Jul 2008 16:16:17 GMT (439kb)

Title: Storage and resonance retrieval of optical superposition states in an
   atomic medium
Authors: Leon Karpa, Frank Vewinger and Martin Weitz
Categories: quant-ph
Comments: 9 pages, 4 figures
   We investigate the storage of light in atomic rubidium vapor using a
multilevel-tripod scheme. In the system, two collective dark polariton modes
exist, forming an effective spinor quasiparticle. Storage of light is performed
by dynamically reducing the optical group velocity to zero. After releasing the
stored pulse, a beating of the two reaccelerated optical modes is monitored.
The observed beating signal oscillates at an atomic transition frequency,
opening the way to novel quantum limited measurements of atomic resonance
frequencies and quantum switches.
\\ ( , 439kb)
Date: Thu, 24 Jul 2008 14:42:02 GMT (473kb)

Title: Direct observation of atom anti-bunching in an optical lattice by
   nearest-neighbor detection
Authors: M. Karski, L. F\"orster, J. M. Choi, W. Alt, A. Widera, D. Meschede
Categories: quant-ph physics.atom-ph
Comments: 4 pages, 4 figures
   We overcome the diffraction limit in fluorescence imaging of neutral atoms in
a one-dimensional optical lattice. At a periodicity of $433 \text{nm}$ we
reliably infer the separation of two atoms down to nearest neighbors. We
observe interaction induced on-site anti-bunching, while for atoms in separate
lattice sites no atom losses due to light induced interactions occur. Our
method points towards characterization of correlated quantum states in optical
lattice systems.
\\ ( , 473kb)
Date: Thu, 24 Jul 2008 18:17:15 GMT (447kb)

Title: Quantum and classical correlations in waveguide lattices
Authors: Y. Bromberg, Y. Lahini, R. Morandotti and Y. Silberberg
Categories: quant-ph
Comments: Comments are welcome
   Lattices of evanescently coupled waveguides have been shown to be extremely
versatile in manipulating the flow of light. These systems enabled direct
observation of optical analogues of fundamental quantum mechanical effects such
as Bloch oscillations, Zenner tunnelling, Anderson localization, the quantum
Zeno effect and many others. These effects however, are not strictly quantum
mechanical, but are rather related to the wave properties of light. To observe
and utilize the quantum properties of light, one should consider correlations
between single photons. In this Letter we investigate photon correlations in
waveguide lattices using two-photon input states. We show that photons
propagating in waveguide lattices develop nontrivial correlations, exhibiting
many non-classical features unique to these systems. Some of these features can
be obtained, albeit with reduced contrast, using classical intensity
correlations measurements, similar to the well known Hanbury Brown and Twiss
correlations. We study experimentally such intensity correlations in a periodic
array. Our results suggest that waveguide lattices can be used as a robust and
highly controllable tool for creating and manipulating quantum states, and
offer new ways of studying the quantum properties of light.
\\ ( , 447kb)

The replacements:

replaced with revised version Fri, 18 Jul 2008 17:41:44 GMT (48kb)

Title: Casimir effect in a one-dimensional gas of free fermions
Authors: Eugene B. Kolomeisky, Joseph P. Straley, and Michael Timmins
Categories: cond-mat.mes-hall hep-th quant-ph
Comments: 13 pages, 5 figures. A generalization to the case of an arbitrary
   harmonic liquid is given and discussion is improved. Version to be published
   in Phys. Rev. A
\\ ( , 48kb)
replaced with revised version Fri, 18 Jul 2008 09:19:51 GMT (148kb)

Title: Ground-state reference systems for expanding correlated fermions in one
Authors: F. Heidrich-Meisner, M. Rigol, A. Muramatsu, A.E. Feiguin, E. Dagotto
Categories: cond-mat.str-el
Comments: 8 pages Revtex4, 7 eps-figures, minor changes, additional references,
   as published
Journal-ref: Phys. Rev. A 78, 013620 (2008)
DOI: 10.1103/PhysRevA.78.013620
\\ ( , 148kb)
replaced with revised version Fri, 18 Jul 2008 13:24:10 GMT (26kb)

Title: Vortex core states in superfluid Fermi-Fermi mixtures with unequal
Authors: M. Iskin
Categories: cond-mat.supr-con cond-mat.other
Comments: 4 pages with 3 figures, to appear in PRA
\\ ( , 26kb)
replaced with revised version Fri, 18 Jul 2008 10:03:23 GMT (96kb)

Title: Atom-atom correlations and relative number squeezing in dissociation of
   spatially inhomogeneous molecular condensates
Authors: Magnus Ogren and K. V. Kheruntsyan
Categories: cond-mat.stat-mech cond-mat.other quant-ph
Comments: Minor corrections, final published version
Journal-ref: Phys. Rev. A 78, 011602(R) (2008)
DOI: 10.1103/PhysRevA.78.011602
\\ ( , 96kb)
replaced with revised version Mon, 21 Jul 2008 07:35:30 GMT (472kb)

Title: The iTEBD algorithm beyond unitary evolution
Authors: Roman Orus, Guifre Vidal
Categories: cond-mat.stat-mech
Comments: 11 pages, 16 figures, 1 appendix with algorithms for specific types
   of evolution. Updated version
\\ ( , 472kb)
replaced with revised version Mon, 21 Jul 2008 14:17:57 GMT (815kb,D)

Title: Quantum Many-Body Dynamics of Coupled Double-Well Superlattices
Authors: Peter Barmettler, Ana Maria Rey, Eugene Demler, Mikhail D. Lukin,
   Immanuel Bloch, Vladimir Gritsev
Categories: quant-ph cond-mat.other cond-mat.str-el
Comments: 13 pages, 10 figures, references added
Journal-ref: Phys. Rev. A 78, 012330 (2008)
DOI: 10.1103/PhysRevA.78.012330
\\ ( , 815kb)
replaced with revised version Sun, 20 Jul 2008 00:20:52 GMT (539kb,D)

Title: Numerical method for evolving the Projected Gross-Pitaevskii equation
Authors: P. B. Blakie
Categories: physics.comp-ph cond-mat.soft physics.atom-ph
Comments: 12 pages, 5 figures. To appear in Phys. Rev. E. Convergence results
   added, a few minor changes made and typos fixed
\\ ( , 539kb)
replaced with revised version Fri, 18 Jul 2008 22:34:48 GMT (57kb)

Title: How the effective boson-boson interaction works in Bose-Fermi mixtures
   in periodic geometries
Authors: Giovanni Mazzarella
Categories: cond-mat.other
\\ ( , 57kb)
replaced with revised version Sun, 20 Jul 2008 10:25:58 GMT (5kb)

Title: Dilute Hard "Sphere" Bose Gas in Dimensions 2, 4 and 5
Authors: C.N. Yang
Categories: cond-mat.stat-mech cond-mat.supr-con
Comments: 3 pages
\\ ( , 5kb)
replaced with revised version Tue, 22 Jul 2008 16:14:05 GMT (309kb)

Title: Spontaneous rotation in one-dimensional systems of cold atoms
Authors: Akiyuki Tokuno, Masahiro Sato
Categories: cond-mat.other cond-mat.str-el
Comments: 6 pages, 3 figures, final version
Journal-ref: Phys. Rev. A 78, 013623 (2008)
DOI: 10.1103/PhysRevA.78.013623
\\ ( , 309kb)
replaced with revised version Tue, 22 Jul 2008 16:36:06 GMT (784kb)

Title: Collisions between tunable halo dimers: exploring an elementary
   four-body process with identical bosons
Authors: F. Ferlaino, S. Knoop, M. Mark, M. Berninger, H. Sch\"obel, H.-C.
   N\"agerl, and R. Grimm
Categories: cond-mat.other
Comments: 4 pages, 4 figures
Journal-ref: Phys. Rev. Lett. 101, 023201 (2008)
DOI: 10.1103/PhysRevLett.101.023201
\\ ( , 784kb)
replaced with revised version Tue, 22 Jul 2008 17:08:24 GMT (58kb)

Title: The two-body problem of ultra-cold atoms in a harmonic trap
Authors: Patrick Shea, Brandon P. van Zyl, Rajat K. Bhaduri
Categories: physics.atom-ph cond-mat.other
\\ ( , 58kb)
replaced with revised version Wed, 23 Jul 2008 04:44:16 GMT (1100kb)

Title: Vortex lattices of bosons in deep rotating optical lattices
Authors: Daniel S. Goldbaum, Erich J. Mueller
Categories: cond-mat.other
Comments: 15 Pages, 5 Figures; Title slightly modified; References updated;
   Organized into sections; Typos corrected; Some discussion added
Journal-ref: Phys. Rev. A 77, 033629 (2008)
DOI: 10.1103/PhysRevA.77.033629
\\ ( , 1100kb)
replaced with revised version Tue, 22 Jul 2008 23:15:40 GMT (632kb)

Title: Breathing mode frequencies of a rotating Fermi gas in the BCS-BEC
   crossover region
Authors: Theja N. De Silva
Categories: cond-mat.other
Comments: 6 pages, 8 fiqures. Formalism is modified to include the effect of
   negative quartic potential
\\ ( , 632kb)
replaced with revised version Tue, 22 Jul 2008 23:08:31 GMT (343kb)

Title: Fermionic superfluid properties in a one-dimensional optical lattice
Authors: Theja N. De Silva
Categories: cond-mat.other
Comments: 6 pages, 5 figures, calculations are modified with different
   tunneling energies
\\ ( , 343kb)
replaced with revised version Thu, 24 Jul 2008 13:21:17 GMT (919kb)

Title: The quasi-periodic Bose-Hubbard model and localization in
   one-dimensional cold atomic gases
Authors: G. Roux, T. Barthel, I. P. McCulloch, C. Kollath, U. Schollwoeck, T.
Categories: cond-mat.str-el cond-mat.dis-nn
Comments: 19 pages, 20 figures
\\ ( , 919kb)
replaced with revised version Thu, 24 Jul 2008 10:55:25 GMT (66kb)

Title: Spatial entanglement of paired photons generated in cold atomic
Authors: Clara I. Osorio, Sergio Barreiro, Morgan W. Mitchell and Juan P.
Categories: quant-ph
Comments: 5 pages, 4 figures. Submitted to Phys. Rev. A.; one figure (Fig. 3)
   was added, typos and labels in figure 2 were corrected
\\ ( , 66kb)

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 Thu Aug 07 2008 - 11:07:53 EST

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