Matt's arXiv selection: week ending 19 December 2008

From: Matthew Davis <>
Date: Wed, 21 Jan 2009 19:12:26 +1000

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

Hi all,

It's been a busy start to the year...

A massive 45 new preprints and 12 replacements this week.

Date: Fri, 12 Dec 2008 13:02:00 GMT (506kb)

Title: Modulational instability of matter waves under strong nonlinearity
Authors: F.Kh. Abdullaev, A.A. Abdumalikov, R.M. Galimzyanov
Categories: cond-mat.other
DOI: 10.1016/j.physd.2008.11.001
   We study modulational instability of matter-waves in Bose-Einstein
condensates (BEC) under strong temporal nonlinearity-management. Both BEC in an
optical lattice and homogeneous BEC are considered in the framework of the
Gross-Pitaevskii equation, averaged over rapid time modulations. For a BEC in
an optical lattice, it is shown that the loop formed on a dispersion curve
undergoes transformation due to the nonlinearity-management. A critical
strength for the nonlinearity-management strength is obtained that changes the
character of instability of an attractive condensate. MI is shown to occur
below(above) the threshold for the positive (negative) effective mass. The
enhancement of number of atoms in the nonlinearity-managed gap soliton is
\\ ( , 506kb)
Date: Fri, 12 Dec 2008 15:22:28 GMT (163kb)

Title: Breached pairing in trapped three-color atomic Fermi gases
Authors: Beatriz Errea, Jorge Dukelsky and Gerardo Ortiz
Categories: cond-mat.supr-con
Comments: 4 pages, 5 figures
   We introduce an exactly solvable model for trapped three-color atom gases.
Applications to a cigar-shaped trapped cold fermions reveal a complex structure
of breached pairing phases. We find two competing superfluid phases at weak and
intermediate couplings, each one with two color pair condensates, that can be
distinguished from density profile measurements.
\\ ( , 163kb)
Date: Fri, 12 Dec 2008 09:19:08 GMT (916kb)

Title: Narrow-band tunable filter based on velocity-selective optical pumping
   in an atomic vapor
Authors: Alessandro Cere, Valentina Parigi, Marta Abad, Florian Wolfgramm, Ana
   Predojevic and Morgan W. Mitchell
Categories: quant-ph
Comments: 3 Pages, 4 figures
   We demonstrate a tunable, narrow-band filter based on optical-pumping-induced
circular dichroism in rubidium vapor. The filter achieves a peak transmission
of 14.6%, a linewidth of 80 MHz, and an out-of-band extinction >35 dB. The
transmission peak can be tuned within the range of the Doppler linewidth of the
D1 line of atomic rubidium at 795 nm. While other atomic filters work at
frequencies far from absorption, the presented technique provides light
resonant with atomic media, useful for atom-photon interaction experiments. The
technique could readily be extended to other alkali atoms.
\\ ( , 916kb)
Date: Fri, 12 Dec 2008 18:14:15 GMT (357kb)

Title: Efficient multiparticle entanglement via asymmetric Rydberg blockade
Authors: M. Saffman and K. Molmer
Categories: quant-ph
Comments: 3 figures
   We present an efficient method for producing $N$ particle entangled states
using Rydberg blockade interactions. Optical excitation of Rydberg states that
interact weakly, yet have a strong coupling to a second control state is used
to achieve state dependent qubit rotations in small ensembles. On the basis of
quantitative calculations we predict that an N=8 Schr\"odinger cat state can be
produced with a fidelity of 84% in cold Rb atoms.
\\ ( , 357kb)
Date: Fri, 12 Dec 2008 05:47:26 GMT (1006kb)

Title: A two-state Raman coupler for coherent atom optics
Authors: J. E. Debs, D. D\''oring, N. P. Robins, C. Figl, P. A. Altin, J. D.
Categories: physics.atom-ph
Comments: 7 Pages, 4 figures
   We present results on a Raman laser-system that resonantly drives a closed
two-photon transition between two levels in different hyperfine ground states
of 87Rb. The coupler is based on a novel optical design for producing two
phase-coherent optical beams to drive a Raman transition. Operated as an
outcoupler, it produces an atom laser in a single internal atomic state, with
the lower divergence and increased brightness typical of a Raman outcoupler.
Due to the optical nature of the outcoupling, the two-state outcoupler is an
ideal candidate for transferring photon correlations onto atom-laser beams. As
our laser system couples just two hyperfine ground states, it has also been
used as an internal state beamsplitter, taking the next major step towards free
space Ramsey interferometry with an atom laser.
\\ ( , 1006kb)
Date: Fri, 12 Dec 2008 08:22:29 GMT (645kb)

Title: A free-space Ramsey interferometer with Bose-condensed atoms
Authors: D. D\"oring, J. E. Debs, N. P. Robins, C. Figl, P. A. Altin, and J. D.
Categories: physics.atom-ph
Comments: 4 pages, 3 figures
   We present results on the development of an atom interferometer operating on
the atomic clock transition |F=1,mF=0> -> |F=2,mF=0> of Bose-condensed 87Rb
atoms. A pulsed atom laser is output-coupled from a Bose-Einstein condensate
and propagates through a sequence of two internal state beam splitters. The
beam splitters are realized via coherent Raman transitions between the two
atomic clock states.
\\ ( , 645kb)
Date: Sun, 14 Dec 2008 12:59:05 GMT (80kb,D)

Title: Statistical physics of power fluctuations in mode locked lasers
Authors: Oded Basis and Omri Gat
Categories: cond-mat.stat-mech
Comments: 7 pages, 1 figure, RevTeX
   We present an analysis of the power fluctuations in the statistical steady
state of a passively mode locked laser. We use statistical light-mode theory to
map this problem to that of fluctuations in a reference equilibrium statistical
physics problem, and in this way study the fluctuations non-perturbatively. The
power fluctuations, being non-critical, are Gaussian and proportional in
amplitude to the inverse square root of the number of degrees of freedom. We
calculate explicit analytic expressions for the covariance matrix of the
overall, pulse and cw power variables, providing complete information on the
single-time power distribution in the laser, and derive a set of
fluctuation-dissipation relations between them and the susceptibilities of the
steady-state quantities.
\\ ( , 80kb)
Date: Mon, 15 Dec 2008 07:56:15 GMT (285kb)

Title: Skyrmion in spinor condensates and its stability in trap potentials
Authors: Akiyuki Tokuno, Yohei Mitamura, Masaki Oshikawa, Igor F. Herbut
Categories: cond-mat.other cond-mat.stat-mech
Comments: 11 pages, 9 figures
   A necessary condition for the existence of a Skyrmion in two-component
Bose-Einstein condensates with $\mathrm{SU(2)}$ symmetry was recently provided
by two of the authors [Phys. Rev. Lett. {\bf 97}, 080403 (2006)], by mapping
the problem to a classical particle in a potential subject to time-dependent
dissipation. Here we further elaborate this approach. For two classes of
models, we demonstrate the existence of the critical dissipation strength above
which the Skyrmion solution does not exist. Furthermore, we discuss the local
stability of the Skyrmion solution by considering the second order variation. A
sufficient condition for the local stability is given in terms of the
groundstate energy of a one-dimensional quantum mechanical Hamiltonian. This
condition requires a minimum number of bosons, for a certain class of the trap
potential. In the optimal case, the minimum number of bosons can be as small as
order of $\sim 10^4$.
\\ ( , 285kb)
Date: Mon, 15 Dec 2008 09:14:55 GMT (751kb)

Title: Observation of Superfluidity of Polaritons in Semiconductor
Authors: A. Amo, J. Lefrere, S. Pigeon, C. Adrados, C. Ciuti, I. Carusotto, R.
   Houdre, E. Giacobino, A. Bramati
Categories: cond-mat.mtrl-sci cond-mat.mes-hall
Comments: 14 pages, 3 figures
   One of the most striking manifestations of quantum coherence in interacting
boson systems is superfluidity. Exciton-polaritons in semiconductor
microcavities are two-dimensional composite bosons predicted to behave as
particular quantum fluids. We report the observation of superfluid motion of
polaritons created by a laser in a semiconductor microcavity. Superfluidity is
investigated in terms of the Landau criterion and manifests itself as the
suppression of scattering from defects when the flow velocity is slower than
the speed of sound in the fluid. On the other hand, a Cerenkov-like wake
pattern is clearly observed when the flow velocity exceeds the speed of sound.
The experimental findings are in excellent quantitative agreement with the
predictions based on a generalized Gross-Pitaevskii theory, showing that
polaritons in microcavities constitute a very rich system for exploring the
physics of non-equilibrium quantum fluids.
\\ ( , 751kb)
Date: Fri, 12 Dec 2008 14:36:34 GMT (23kb)

Title: Quantum mechanical evolution towards thermal equilibrium
Authors: Noah Linden, Sandu Popescu, Anthony J. Short, Andreas Winter
Categories: quant-ph cond-mat.stat-mech
Comments: 12.1 pages
   The circumstances under which a system reaches thermal equilibrium, and how
to derive this from basic dynamical laws, has been a major question from the
very beginning of thermodynamics and statistical mechanics. Despite
considerable progress, it remains an open problem. Motivated by this issue, we
address the more general question of equilibration. We prove, with virtually
full generality, that reaching equilibrium is a universal property of quantum
systems: Almost any subsystem in interaction with a large enough bath will
reach an equilibrium state and remain close to it for almost all times. We also
prove several general results about other aspects of thermalisation besides
equilibration, for example, that the equilibrium state does not depend on the
detailed micro-state of the bath.
\\ ( , 23kb)
Date: Sat, 13 Dec 2008 04:14:14 GMT (19kb)

Title: Approach to Thermal Equilibrium in the Caldeira-Leggett Model
Authors: Fethi M Ramazanoglu
Categories: quant-ph
Comments: 26 pages, no figures
   We provide an explicit analytical calculation that shows the asymptotic
approach of the one dimensional Caldeira-Leggett model to thermal equilibrium
in the high temperature and weak coupling limit. We investigate a free particle
and a harmonic oscillator system, using both the Lindblad and the non-Lindblad
type master equations for each case, and show that thermal equilibrium is
reached exactly for the free particle and aproximately for the harmonic
oscillator, irrespective of the initial preparation of the system. We also
generalize our calculation to higher dimensions.
\\ ( , 19kb)
Date: Sat, 13 Dec 2008 20:55:12 GMT (106kb)

Title: A proposal of implementing Hardy's thought-experiment with particles
   that never met
Authors: Sofia Wechsler
Categories: quant-ph
Comments: 5 pages, 2 figures
   Hardy's thought-experiment is the strongest argument against the idea of
continuous trajectories of particles from the source to the detector. This idea
seems to result as an unavoidable conclusion from some simple experiments. In
its original form, Hardy's thought-experiment was proposed for two independent
particles, a positron and an electron. The two either meet and annihilate, or
don't meet but become entangled. An important feature of entanglements with
particles that never meet is the difficulty they raise in front of the
assumption of "hidden communication" between the particles. Indeed, if the
particles don't meet, they can't have information of one another and it is
difficult to explain how can they communicate. In order to implement Hardy's
paradox with particles that never meet, the present article proposes to use
photons from three different lasers, one laser emitting UV rays, and the other
two emitting at the wavelength of the signal photon, respectively the idler
photon obtained from the down-conversion of the UV rays. The role of the
annihilation in Hardy's experiment will be played by the destructive
interference between a down-conversion pair and two photons from the low-energy
\\ ( , 106kb)
Date: Sun, 14 Dec 2008 11:48:40 GMT (1355kb)

Title: Connection between Wigner distribution of nonclassical fields and
   collapse-revival of atomic dynamics
Authors: C. H. Raymond Ooi
Categories: quant-ph
Comments: 5 pages, 4 figures
   The transient evolution of nonclassical radiation fields interacting with an
atom in a cavity is correlated to the atomic dynamics. Connection between the
atomic phases of collapse and revival, and the Wigner function pattern is
explored. Initial classical coherent field can evolve into nonclassical field.
Schrodinger cat state field is generate during the atomic collapse phase. For
initial Schrodinger cat field state, the state dissolves with time but revives
during the atomic phase that corresponds with the initial phase. More intricate
but orderly characteristics are found between the collapse-revival dynamics and
the patterns of the Wigner function for initial thermal field.
\\ ( , 1355kb)
Date: Mon, 15 Dec 2008 11:53:51 GMT (149kb)

Title: Two Mode Photon Bunching Effect as Witness of Quantum Criticality in
   Circuit QED
Authors: Qing Ai, Ying-Dan Wang, Guilu Long, C. P. Sun
Categories: quant-ph
Comments: 7 pages, 4 figures
   We suggest a scheme to probe critical phenomena at a quantum phase transition
(QPT) using the quantum correlation of two photonic modes simultaneously
coupled to a critical system. As an experimentally accessible physical
implementation, a circuit QED system is formed by a capacitively coupled
Josephson junction qubit array interacting with one superconducting
transmission line resonator (TLR). It realizes an Ising chain in the transverse
field (ICTF) which interacts with the two magnetic modes propagating in the
TLR. We demonstrate that in the vicinity of criticality the originally
independent fields tend to display photon bunching effects due to their
interaction with the ICTF. Thus, the occurrence of the QPT is reflected by the
quantum characteristics of the photonic fields.
\\ ( , 149kb)
Date: Mon, 15 Dec 2008 01:52:38 GMT (1221kb,D)

Title: Electro-Optical Nano-Traps for Neutral Atoms
Authors: Brian Murphy and Lene Vestergaard Hau
Categories: physics.atom-ph
Comments: 11 pages, 3 figures
   We propose a new class of nanoscale electro-optical traps for neutral atoms.
A prototype is the toroidal trap created by a suspended, charged carbon
nanotube decorated with a silver nanosphere dimer. An illuminating laser field,
blue detuned from an atomic resonance frequency, is strongly focused by
plasmons induced in the dimer and generates both a repulsive potential barrier
near the nanostructure surface and a large viscous damping force that
facilitates trap loading. Atoms with velocities of several meters per second
may be loaded directly into the trap via spontaneous emission of just two
\\ ( , 1221kb)
Date: Sun, 14 Dec 2008 09:19:39 GMT (195kb)

Title: Vacuum squeezed light for atomic memories at the D2 cesium line
Authors: Sidney Burks (LKB - Jussieu), Alberto Bramati (LKB - Jussieu),
   Elisabeth Giacobino (LKB - Jussieu), Julien Laurat (LKB - Jussieu),
   J\'er\'emie Ortalo (LKB - Jussieu), Xiaojun Jia (LKB - Jussieu), Fabrizio
   Villa (LKB - Jussieu), Antonino Chuimmo (LKB - Jussieu)
Categories: physics.optics
   We report the experimental generation of squeezed light at 852 nm, locked on
the Cesium D2 line. 50% of noise reduction down to 50 kHz has been obtained
with a doubly resonant optical parametric oscillator operating below threshold,
using a periodically-polled KTP crystal. This light is directly utilizable with
Cesium atomic ensembles for quantum networking applications
\\ ( , 195kb)
Date: Tue, 16 Dec 2008 02:26:30 GMT (280kb)

Title: Paired states in spin-imbalanced atomic Fermi gases in one dimension
Authors: Paata Kakashvili and C. J. Bolech
Categories: cond-mat.other cond-mat.str-el
Comments: 4 pages, 2 figures
   A growing expertise to engineer, manipulate and probe different cold-atom
analogs of electronic condensed matter systems allows to probe properties of
exotic pairing. We study paired states of spin-imbalanced ultracold atomic
system of fermions with attractive short-range interactions in one-dimensional
traps. Calculations are done using the Bethe Ansatz technique and the trap is
incorporated into the solution via a local density approximation. The
thermodynamic-Bethe-Ansatz equations are solved numerically and different local
density profiles are calculated for zero and finite temperatures. A procedure
to identify the homogeneous-system phase diagram using local density profiles
in the trap is also proposed. Such scheme would be immediately useful for the
\\ ( , 280kb)
Date: Tue, 16 Dec 2008 05:44:14 GMT (13kb)

Title: Exact solution of the infinite-U Hubbard problem and other models in one
Authors: Brijesh Kumar
Categories: cond-mat.str-el
Comments: revtex4, 6 pages, no figures; submitted to Phys. Rev. B
   An interacting spin-fermion model is exactly solved on an open chain. In a
certain representation, it is the nearest-neighbor Hubbard model in the limit
of infinite $U$ (local interaction). Exact solution of its complete energy
eigen-spectrum is accomplished by introducing a unitary transformation which
maps the original problem to a tight-binding model of the fermions only.
Physically, the exact solution implies the absence of Nagaoka ferromagnetism in
the ground state for arbitrary electron densities. The present method solves a
class of very general models exactly. Few more problems are discussed as an
application of this unitary transform method.
\\ ( , 13kb)
Date: Tue, 16 Dec 2008 09:10:37 GMT (116kb)

Title: Trap modulation spectroscopy of the Mott-insulator transition in optical
Authors: H. Lignier and A. Zenesini and D. Ciampini and O. Morsch and E.
   Arimondo and S. Montangero and G. Pupillo and R. Fazio
Categories: cond-mat.other
Comments: 5 pages, 5 figures
   We introduce a new technique to probe the properties of an interacting cold
atomic gas that can be viewed as a dynamical compressibility measurement. We
apply this technique to the study of the superfluid to Mott insulator quantum
phase transition in one and three dimensions for a bosonic gas trapped in an
optical lattice. Excitations of the system are detected by time-of-flight
measurements. The experimental data for the one-dimensional case are in good
agreement with the results of a time-dependent density matrix renormalization
group calculation.
\\ ( , 116kb)
Date: Tue, 16 Dec 2008 11:19:53 GMT (349kb)

Title: Rotational Fluxons of Bose-Einstein Condensates in Coplanar Double-Ring
Authors: J. Brand, T. J. Haigh, U. Z\"ulicke
Categories: cond-mat.other cond-mat.mes-hall
Comments: 4 pages, 3 figures
   We investigate the ground-state properties and nonlinear dynamics of rotating
co-planar tunnel-coupled annular Bose-Einstein condensates (BECs). Intriguing
condensate-phase structure emerges due to a competition between coherent
tunneling and the difference of centrifugal potentials in the two rings. As a
result, rotational analogs to magnetic fluxons in conventional Josephson
junctions can exist in the ground state of double-ring BECs. Spatial and
temporal variations of the potential difference between the two rings turn out
to induce fluxon motion. The observation of macroscopic quantum tunneling in
this system appears feasible. Our numerical studies are complemented by an
effective hydrodynamic description of the fluxon dynamics.
\\ ( , 349kb)
Date: Tue, 16 Dec 2008 11:54:52 GMT (1020kb)

Title: The Theory of Fermi Condensate Quantum Phase Transition
Authors: Konstantin Popov
Categories: cond-mat.str-el
Comments: 75 pages, 46 figures, in Russian
   This report is devoted to the building of the theory and analyzing the
phenomenon which take place in such strong correlated Fermi systems as High
temperature superconductors, metals with heavy fermions and quasi two
dimensional Fermi-systems. The described theory of strong correlated Fermi
systems bases on conceptions of Fermi condensate quantum phase transition
(FCQPT) and Fermi condensate. It develops the well known Landau paradigm based
on quasi particles formalism and order parameter. The description of the FCQPT
theory is followed by its verification on the different exactly solvable
models, by numerical calculations and by comparing with wide collection of
experimental data.
\\ ( , 1020kb)
Date: Tue, 16 Dec 2008 16:10:49 GMT (80kb)

Title: Two-component gap solitons with linear interconversion
Authors: Sadhan K. Adhikari and Boris A. Malomed
Categories: cond-mat.other
Comments: 4 pages, 9 figures
   We consider one-dimensional solitons in a binary Bose-Einstein condensate
with linear coupling between the components, trapped in an optical-lattice
potential. The inter-species and intra-species interactions may be both
repulsive or attractive. Main effects considered here are spontaneous breaking
of the symmetry between components in symmetric and antisymmetric solitons, and
spatial splitting between the components. These effects are studied by means of
a variational approximation and numerical simulations.
\\ ( , 80kb)
Date: Tue, 16 Dec 2008 17:39:47 GMT (149kb)

Title: Hydrodynamics of superfluids confined in blocked rings and wedges
Authors: Chandan Dasgupta and Oriol T. Valls
Categories: cond-mat.other cond-mat.stat-mech
Comments: 15 pages, including figures. To appear in Phys. Rev. E
   Motivated by many recent experimental studies of non-classical rotational
inertia (NCRI) in superfluid and supersolid samples, we present a study of the
hydrodynamics of a superfluid confined in the two-dimensional region
(equivalent to a long cylinder) between two concentric arcs of radii $b$ and
$a$ ($b<a$) subtending an angle $\beta$, with $0 \le \beta \le 2\pi$. The case
$\beta= 2 \pi$ corresponds to a blocked ring. We discuss the methodology to
compute the NCRI effects, and calculate these effects both for small angular
velocities, when no vortices are present, and in the presence of a vortex. We
find that, for a blocked ring, the NCRI effect is small, and that therefore
there will be a large discontinuity in the moment of inertia associated with
blocking or unblocking circular paths. For blocked wedges ($b=0$) with $\beta >
\pi$, we find an unexpected divergence of the velocity at the origin, which
implies the presence of either a region of normal fluid or a vortex for {\it
any} nonzero value of the angular velocity. Implications of our results for
experiments on "supersolid" behavior in solid $^4{\rm He}$ are discussed. A
number of mathematical issues are pointed out and resolved.
\\ ( , 149kb)
Date: Tue, 16 Dec 2008 18:18:26 GMT (102kb)

Title: Finite-Temperature Behavior of an Inter-species Fermionic Superfluid
   with Population Imbalance
Authors: Hao Guo, Chih-Chun Chien, Qijin Chen, Yan He, and K. Levin
Categories: cond-mat.other cond-mat.supr-con
Comments: 4 pages, 4 figures
   We determine the superfluid transition temperature $T_c$ and related finite
temperature phase diagrams for the entire BCS-Bose Einstein condensation
crossover in a homogeneous mixture of $^{6}$Li and $^{40}$K atoms with
population imbalance. Our work is motivated by the recent observation of an
inter-species Feshbach resonance. Pairing fluctuation effects, which
significantly reduce $T_c$ from the onset temperature for pairing ($T^*$),
provide reasonable estimates of $T_c$ and indicate that the inter-species
superfluid phase should be accessible in future experiments. Although a
generalized-Sarma phase is not stable in the ground state near unitarity, our
phase diagrams show that it appears as an intermediate-temperature superfluid.
\\ ( , 102kb)
Date: Tue, 16 Dec 2008 20:27:42 GMT (11kb)

Title: Trial wave functions, molecular states, and ro-vibrational spectra in
   the lowest Landau level: A universal description for bosons and fermions
Authors: Constantine Yannouleas, Uzi Landman
Categories: cond-mat.mes-hall
Comments: 5 pages with two tables. Revtex
   Through the introduction of a class of appropriate translationally invariant
trial wave functions, we show that the strong correlations in the lowest Landau
level (LLL) reflect in finite systems the emergence of intrinsic point-group
symmetries associated with rotations and vibrations of molecules formed through
particle localization. This molecular description is universal, being valid for
both bosons and fermions, for both the yrast and excited states of the LLL
spectra, and for both low and high angular momenta. This physical picture is
fundamentally different from the "quantum-fluid" one associated with
Jastrow-type trial functions.
\\ ( , 11kb)
Date: Thu, 12 Oct 2006 13:58:24 GMT (248kb)

Title: A class of quantum many-body states that can be efficiently simulated
Authors: G. Vidal
Categories: quant-ph cond-mat.str-el
Comments: 4 pages, 5 figures
Journal-ref: Phys. Rev. Lett. 101, 110501 (2008)
   We introduce the multi-scale entanglement renormalization ansatz (MERA), an
efficient representation of certain quantum many-body states on a D-dimensional
lattice. Equivalent to a quantum circuit with logarithmic depth and distinctive
causal structure, the MERA allows for an exact evaluation of local expectation
values. It is also the structure underlying entanglement renormalization, a
coarse-graining scheme for quantum systems on a lattice that is focused on
preserving entanglement.
\\ ( , 248kb)
Date: Tue, 16 Dec 2008 15:44:52 GMT (216kb)

Title: Efficient formation of ground state ultracold molecules via STIRAP from
   the continuum at a Feshbach resonance
Authors: Elena Kuznetsova, Susanne F. Yelin, Marko Gacesa, Philippe Pellegrini,
   Robin C\^ot\'e
Categories: quant-ph
   We develop a complete theoretical description of photoassociative Stimulated
Raman Adiabatic Passage (STIRAP) near a Feshbach resonance in a thermal atomic
gas. We show that it is possible to use low intensity laser pulses to directly
excite the continuum at a Feshbach resonance and transfer nearly the entire
atomic population to the lowest rovibrational level in the molecular ground
state. In case of a broad resonance, commonly found in several diatomic alkali
molecules, our model predicts a transfer efficiency $\eta$ up to 97% for a
given atom pair, and up to 70% when averaged over an atomic ensemble. The laser
intensities and pulse durations needed for optimal transfer are $10^2-10^3$
W/cm$^2$ and several $\mu$s. Such efficiency compares to or surpasses currently
available techniques for creating stable diatomic molecules, and the
versatility of this approach simplifies its potential use for many molecular
\\ ( , 216kb)
Date: Tue, 16 Dec 2008 20:33:00 GMT (57kb)

Title: Algorithm for simulation of quantum many-body dynamics using dynamical
   coarse graining
Authors: M. Khasin and R. Kosloff
Categories: quant-ph
Comments: 22 pages, 4 figures, submitted to Phys. Rev. A
   An algorithm for simulating the dynamics of a restricted set of observables
of a many-body system is presented. The set comprises the spectrum-generating
algebra (SGA) of observables of the system. The technical development of the
algorithm is based on the close connection between the algebra of observables
and the set of states minimizing the generalized uncertainty with respect to
these observables -- the generalized coherent states (GCS). These states serve
as dynamical basis functions for expanding the state of the system. The
original unitary dynamics of the observables is simulated by a surrogate
open-system dynamics, which can be interpreted as a weak measurement of the
elements of the SGA, performed on the evolving system. The measurement leads to
a coarse-graining of the evolving state in the corresponding phase-space. The
coarse-grained state can be represented as a mixture of pure states, localized
in the phase-space. The evolution of the pure states is governed by the
stochastic nonlinear Schroedinger equation (sNLSE), which can be simulated at
dramatically lower computational cost using expansion of the localized
solutions in the basis of the GCS. The algorithm is applied to the simulation
of the dynamics of a system of 2*10^4 cold atoms in the double-well trap,
described by the two-sites Bose-Hubbard model.
\\ ( , 57kb)
Date: Tue, 16 Dec 2008 20:17:52 GMT (324kb)

Title: Determination of the fine structure constant with atom interferometry
   and Bloch oscillations
Authors: Malo Cadoret (LKB - Jussieu), Estefania De Mirandes (LKB - Jussieu),
   Pierre Clad\'e (LKB - Jussieu), Catherine Schwob (LKB - Jussieu),
   Fran\c{c}ois Nez (LKB - Jussieu), Lucile Julien (LKB - Jussieu), Fran\c{c}ois
   Biraben (LKB - Jussieu), Sa\"ida Guellati-Kh\'elifa (BNM-INM)
Categories: physics.atom-ph
   We use Bloch oscillations to transfer coherently many photon momenta to
atoms. Then we can measure accurately the recoil velocity $\hbar k/m$ and
deduce the fine structure constant $\alpha$. The velocity variation due to
Bloch oscillations is measured using atom interferometry. This method yields to
a value of the fine structure constant $\alpha^{-1}= 137.035 999 45 (62)$ with
a relative uncertainty of about $4.5 \times 10^{-9}$.
\\ ( , 324kb)
Date: Wed, 17 Dec 2008 07:44:47 GMT (803kb)

Title: Symmetry Breaking and Self-trapping of a Dipolar Bose-Einstein
   Condensate in a Double-well Potential
Authors: Bo Xiong, Jiangbin Gong, Han Pu, Weizhu Bao, and Baowen Li
Categories: cond-mat.other
Comments: 9 pages, 5 figures, to appear in Physical Review A
   The quantum self-trapping phenomenon of a Bose-Einstein condensate (BEC)
represents a remarkable nonlinear effect of wide interest. By considering a
purely dipolar BEC in a double-well potential, we study how the dipole
orientation affects the ground state structure and the transition between
self-trapping and Josephson oscillation in dynamics. Three-dimensional
numerical results and an effective two-mode model demonstrate that the onset of
self-trapping of a dipolar BEC can be radically modified by the dipole
orientation. We also analyze the failure of the two-mode model in predicting
the rate of Josephson oscillations. We hope that our results can motivate
experimental work as well as future studies of self-trapping of ultracold
dipolar gases in optical lattices.
\\ ( , 803kb)
Date: Wed, 17 Dec 2008 11:46:43 GMT (235kb)

Title: Dynamic and static density-density correlations in the one-dimensional
   Bose gas: exact results and approximations
Authors: Alexander Yu. Cherny and Joachim Brand
Categories: cond-mat.stat-mech cond-mat.mes-hall
Comments: 8 pages, 6 figures
   We discuss approximate formulas for the dynamic structure factor of the
one-dimensional Bose gas in the Lieb-Liniger model that appear to be applicable
over a wide range of the relevant parameters such as the interaction strength,
frequency, and wavenumber. The suggested approximations are consistent with the
exact results known in limiting cases. In particular, we encompass exact edge
exponents as well as Luttinger liquid and perturbation theoretic results. We
further discuss derived approximations for the static structure factor and the
pair distribution function g(x). The approximate expressions show excellent
agreement with numerical results based on the algebraic Bethe ansatz.
\\ ( , 235kb)
Date: Wed, 17 Dec 2008 13:22:08 GMT (664kb)

Title: Observation of interspecies Feshbach resonances in an ultracold Rb-Cs
Authors: K. Pilch, A. D. Lange, A. Prantner, G. Kerner, F. Ferlaino, H.-C.
   Naegerl, and R. Grimm
Categories: cond-mat.other
Comments: 7 pages, 3 figures, 1 table
   We report on the observation of interspecies Feshbach resonances in an
ultracold, optically trapped mixture of Rb and Cs atoms. In a magnetic field
range up to 300 G we find 23 interspecies Feshbach resonances in the lowest
spin channel and 2 resonances in a higher channel of the mixture. The
extraordinarily rich Feshbach spectrum suggests the importance of different
partial waves in both the open and closed channels of the scattering problem
along with higher-order coupling mechanisms. Our results provide, on one hand,
fundamental experimental input to characterize the Rb-Cs scattering properties
and, on the other hand, identify possible starting points for the association
of ultracold heteronuclear RbCs molecules.
\\ ( , 664kb)
Date: Thu, 18 Dec 2008 07:16:15 GMT (198kb)

Title: A geometrical approach to hydrodynamics and low-energy excitations of
   spinor condensates
Authors: Ryan Barnett, Daniel Podolsky, and Gil Refael
Categories: cond-mat.other cond-mat.str-el
Comments: 21 pages, 4 figures
   In this paper, we derive the equations of motion governing the dynamics of
spin-$F$ spinor condensates. We write the equations of motion in terms of the
standard physical variables (total density and superfluid velocity), alongside
2F `spin-nodes': unit vectors that describe the spin-F state, and also exhibit
the point-group symmetry of a spinor condensate's mean-field ground state. In
the first part of our analysis, we derive the hydrodynamic equations of motion,
which consist of a mass continuity equation, 2F Landau-Lifshitz equations for
the spin-nodes, and a modified Euler equation. In particular, we provide a
generalization of the Mermin-Ho relation to spin-one, and find an analytic
solution for the skyrmion texture in the incompressible regime of a spin-half
condensate. In the second part, we linearize the equations of motion
determining the low lying spin-waves of the condensate. Using the spin-node
formalism, we connect the normal spin-wave excitations with the emergent
symmetry of the spinor-condensate ground state, and provide a simple
construction that allows their extraction from symmetry considerations alone.
These results demonstrate the beautiful geometrical structure that underlies
the dynamics of spinor condensates.
\\ ( , 198kb)
Date: Wed, 17 Dec 2008 21:55:57 GMT (880kb)

Title: Disorder-induced superfluidity
Authors: Long Dang, Massimo Boninsegni and Lode Pollet
Categories: cond-mat.dis-nn cond-mat.stat-mech
Comments: 4 pages, 5 figures
   We use quantum Monte Carlo simulations to study the phase diagram of
hard-core bosons with short-ranged attractive interactions, in the presence of
uniform diagonal disorder. It is shown that moderate disorder stabilizes a
glassy superfluid phase in a range of values of the attractive interaction for
which the system is a Mott insulator, in the absence of disorder. A transition
to an insulating Bose glass phase occurs as the strength of the disorder
\\ ( , 880kb)
Date: Thu, 18 Dec 2008 19:05:27 GMT (121kb)

Title: Finite-size and confinement effects in spin-polarized trapped Fermi
Authors: Mark Ku, Jens Braun, Achim Schwenk
Categories: cond-mat.other
Comments: 4 pages, 3 figures
   We calculate the energy of a single fermion interacting resonantly with a
Fermi sea of different-species fermions in asymmetric traps, and show that
finite particle numbers and the trap geometry impact the phase structure and
the critical polarization. Our findings contribute to understanding some
experimental discrepancies in spin-polarized Fermi gases as finite-size and
confinement effects.
\\ ( , 121kb)
Date: Thu, 18 Dec 2008 02:51:52 GMT (1223kb)

Title: Seeing Anderson Localization
Authors: M. Hilke
Categories: cond-mat.dis-nn cond-mat.mtrl-sci
Comments: 5 pages, 4 figures
   Anderson localization was discovered 50 years ago to describe the propagation
of electrons in the presence of disorder. The main prediction back then, was
the existence of disorder induced localized states, which do not conduct
electricity. Many years later it turns out, that the concept of Anderson
localization is much more general and applies to almost any type of propagation
in time or space, when more than one parameter is relevant (like phase and
amplitude). Here we propose a new optical scheme to literally see Anderson
localization by varying the optical wavelength or angle of incidence to tune
between localized and delocalized states. The occurrence of Anderson
localization in the propagation of light, in particular, has become the focus
of tremendous interest due to the emergence of new optical technologies and
media, such as low dimensional and disordered optical lattices. While several
experiments have reported the measurement of Anderson localization of light,
many of the observations remain controversial because the effects of absorption
and localization have a similar signature, i.e., exponential decrease of the
transmission with the system size. In this work, we discuss a system, where we
can clearly differentiate between absorption and localization effects because
this system is equivalent to a perfect filter, only in the absence of any
absorption. Indeed, only one wavelength is perfectly transmitted and all others
are fully localized. These results were obtained by developing a new
theoretical framework for the average optical transmission through disordered
\\ ( , 1223kb)
Date: Thu, 18 Dec 2008 08:51:10 GMT (150kb)

Title: Superfluidity and Anderson localisation for a weakly interacting Bose
   gas in a quasiperiodic potential
Authors: Xiaolong Deng (LPM2C), Roberta Citro (Salerno), Anna Minguzzi (LPM2C),
   Edmond Orignac (ENS-Lyon)
Categories: cond-mat.mes-hall cond-mat.other
Comments: 12 pages, 9 figures, RevTeX 4
   Using exact diagonalisation and Density Matrix Renormalisation group (DMRG)
approach, we analyse the transition to a localised state of a weakly
interacting quasi-1D Bose gas subjected to a quasiperiodic potential. The
analysis is performed by calculating the superfluid fraction, density profile,
momentum distribution and visibility for different periodicities of the second
lattice and in the presence (or not) of a weak repulsive interaction. It is
shown that the transition is sharper towards the maximally incommensurate ratio
between the two lattice periodicities, and shifted to higher values of the
second lattice strength by weak repulsive interactions. We also relate our
results to recent experiments.
\\ ( , 150kb)
Date: Thu, 18 Dec 2008 10:20:01 GMT (1344kb)

Title: Dipole Oscillations of a Fermi Gas in a Disordered Trap: Damping and
Authors: Luca Pezz\'e, Ben Hambrecht, Laurent Sanchez-Palencia
Categories: cond-mat.other
Comments: 4 pages, 4 figures
   We study the dipole oscillations of an ideal Fermi gas in a disordered trap.
We show that even weak disorder induces strong damping of the oscillations and
we identify a metal-insulator crossover: For very weak disorder, we find
under-damping and show that it results from weak random perturbations of the
energy spectrum. For increasing disorder, we show that the Fermi gas crosses
over to a strongly insulating regime characterized by over-damping resulting
from the proliferation of localized states.
\\ ( , 1344kb)
Date: Thu, 18 Dec 2008 14:38:03 GMT (43kb)

Title: Hybrid multi-site excitations in dipolar condensates in optical lattices
Authors: M. Klawunn and L. Santos
Categories: cond-mat.other
Comments: 4 pages, 6 figures
   Strong 1D lattices usually lead to unconnected two-dimensional gases. The
long-range character of the dipole-dipole interactions leads to a novel
scenario where non-overlapping gases at different sites may interact
significantly. We show that the excitations of non-overlapping condensates in
1D optical lattices acquire a band-like character, being collectively shared by
different sites. In particular, the hybridization of the modes significantly
enhances the rotonization of the excitations, and may induce roton-instability.
We discuss the observability of this effect in on-going experiments.
\\ ( , 43kb)
Date: Thu, 18 Dec 2008 16:11:59 GMT (866kb)

Title: Formation of dynamical Schr\"odinger cats in low-dimensional ultracold
   attractive Bose gases
Authors: Alexej I. Streltsov, Ofir E. Alon, and Lorenz S. Cederbaum
Categories: cond-mat.other
Comments: 11 pages, 3 figures
   Dynamical Schr\"odinger cats can be formed when a one-dimensional attractive
Bose-gas cloud is scattered off a potential barrier. Once formed, these objects
are stable in time. The phenomenon and its mechanism -- transformation of
kinetic energy to internal energy of the scattered atomic cloud -- are obtained
by solving the time-dependent many-boson Schr\"odinger equation. Implications
are discussed.
\\ ( , 866kb)
Date: Thu, 18 Dec 2008 19:42:28 GMT (736kb)

Title: Hybrid 2D surface trap for quantum simulation
Authors: J.I. Gillen, W. S. Bakr, A. Peng, P. Unterwaditzer, S. Foelling, M.
Categories: cond-mat.other
Comments: 5 pages, 4 figures
   We demonstrate a novel optical trapping scheme for ultracold atoms. Using a
combination of evanescent wave, standing wave, and magnetic potentials we
create a deeply 2D Bose-Einstein condensate (BEC) at a few microns from a glass
surface. Using techniques such as broadband "white" light to create evanescent
and standing waves, we realize a smooth potential with a trap frequency aspect
ratio of 300:1:1 and long lifetimes. This makes the setup suitable for
many-body quantum simulations and applications such as high precision
measurements close to surfaces.
\\ ( , 736kb)
Date: Thu, 18 Dec 2008 20:25:50 GMT (69kb)

Title: Large Amplitude Dynamics of the Pairing Correlations in a Unitary Fermi
Authors: Aurel Bulgac and Sukjin Yoon
Categories: cond-mat.stat-mech cond-mat.supr-con
Comments: 4 pages, 3 figures
   A unitary Fermi gas has a surprisingly rich spectrum of large amplitude modes
of the pairing field alone, which defies a description within a formalism
involving only a reduced set of degrees of freedom, such as quantum
hydrodynamics or a Landau-Ginzburg like description. These modes are very slow,
with oscillation frequencies well below the pairing gap, which makes their
coupling with quasiparticle excitations quite ineffective. In atomic traps
these modes couple naturally with the density oscillations, and the
corresponding oscillations of the atomic cloud are an example of a new type of
collective mode in Fermi systems. They have slower frequencies than the
compressional collective hydrodynamic oscillations, have a non-spherical
momentum distribution, and they could be excited by a quick time variation of
the scattering length.
\\ ( , 69kb)
arXiv:0812.2611 (*cross-listing*)
Date: Sun, 14 Dec 2008 09:19:39 GMT (195kb)

Title: Vacuum squeezed light for atomic memories at the D2 cesium line
Authors: Sidney Burks (LKB - Jussieu), Alberto Bramati (LKB - Jussieu),
   Elisabeth Giacobino (LKB - Jussieu), Julien Laurat (LKB - Jussieu),
   J\'er\'emie Ortalo (LKB - Jussieu), Xiaojun Jia (LKB - Jussieu), Fabrizio
   Villa (LKB - Jussieu), Antonino Chuimmo (LKB - Jussieu)
Categories: physics.optics quant-ph
   We report the experimental generation of squeezed light at 852 nm, locked on
the Cesium D2 line. 50% of noise reduction down to 50 kHz has been obtained
with a doubly resonant optical parametric oscillator operating below threshold,
using a periodically-polled KTP crystal. This light is directly utilizable with
Cesium atomic ensembles for quantum networking applications
\\ ( , 195kb)
Date: Thu, 18 Dec 2008 18:49:44 GMT (364kb)

Title: New Measurement of the 2S Hyperfine Interval in Atomic Hydrogen
Authors: N. Kolachevsky, A. Matveev, J. Alnis, C.G. Parthey, S.G. Karshenboim,
   T.W. Haensch
Categories: physics.atom-ph
Comments: 5 pages, 4 figures
   An optical measurement of the 2S hyperfine interval in atomic hydrogen using
two-photon spectroscopy of the 1S-2S transition gives a value of 177 556
834.3(6.7) Hz. The uncertainty is 2.4 times less than achieved by our group in
2003 and more than 4 times less than for any independent radio-frequency
measurement. The specific combination of the 1S and 2S hyperfine intervals
predicted by QED theory $D_{21}=48 953(3)$ Hz is in perfect agreement with the
value $48 923(54)$ obtained from this experiment.
\\ ( , 364kb)
Date: Thu, 18 Dec 2008 00:38:22 GMT (409kb)

Title: Stable higher-charge discrete vortices in hexagonal optical lattices
Authors: Kody J.H. Law, P. G. Kevrekidis, Tristram J. Alexander, Wieslaw
   Krolikowski, and Yuri S. Kivshar
Categories: physics.optics
   We show that double-charge discrete optical vortices may be completely stable
in hexagonal photonic lattices where single-charge vortices always exhibit
dynamical instabilities. Even when unstable the double-charge vortices
typically have a much weaker instability than the single-charge vortices, and
thus their breakup occurs at longer propagation distances.
\\ ( , 409kb)

The replacements:

replaced with revised version Fri, 12 Dec 2008 11:29:05 GMT (66kb)

Title: Probing ultra-cold Fermi atoms with a single ion
Authors: Y. Sherkunov, B. Muzykantskii, N. d'Ambrumenil, B.D Simons
Categories: cond-mat.str-el
Comments: 5 pages, 2 figures
\\ ( , 66kb)
replaced with revised version Fri, 12 Dec 2008 11:35:48 GMT (45kb)

Title: Effective Nonlinear Schr\"odinger Equations for Cigar-Shaped and
   Disk-Shaped Fermi Superfluids at Unitarity
Authors: S. K. Adhikari and L. Salasnich
Categories: cond-mat.other
Comments: 22 pages, 5 figures
\\ ( , 45kb)
replaced with revised version Sat, 13 Dec 2008 21:26:31 GMT (776kb)

Title: Three-body Interactions in one Dimension
Authors: B. Capogrosso-Sansone, S. Wessel, H.P. B\"uchler, P. Zoller, and G.
Categories: cond-mat.other
Comments: 5 pages, 4 figures, minor changes in the text
\\ ( , 776kb)
arXiv:0804.3501 (*cross-listing*)
replaced with revised version Sat, 13 Dec 2008 13:55:50 GMT (799kb)

Title: Lattice simulations for few- and many-body systems
Authors: Dean Lee (North Carolina State University)
Categories: nucl-th cond-mat.other hep-lat
Comments: 71 pages, 20 figures, published version to appear in Progress in
   Particle and Nuclear Physics
\\ ( , 799kb)
replaced with revised version Fri, 12 Dec 2008 23:44:49 GMT (324kb)

Title: Magneto-Optical Trap for Polar Molecules
Authors: Benjamin K. Stuhl, Brian C. Sawyer, Dajun Wang, Jun Ye
Categories: physics.atom-ph physics.chem-ph physics.optics
Comments: 4 pages, 4 figures, 1 table v2: updated to final published text and
Journal-ref: Phys. Rev. Lett. 101, 243002 (2008)
DOI: 10.1103/PhysRevLett.101.243002
\\ ( , 324kb)
replaced with revised version Tue, 16 Dec 2008 13:30:04 GMT (693kb)

Title: Quantum critical behavior in strongly interacting Rydberg gases
Authors: Hendrik Weimer, Robert L\"ow, Tilman Pfau, Hans Peter B\"uchler
Categories: quant-ph cond-mat.mes-hall cond-mat.stat-mech
Comments: 4 pages, 3 figures, published version
Journal-ref: Phys. Rev. Lett. 101, 250601 (2008)
DOI: 10.1103/PhysRevLett.101.250601
\\ ( , 693kb)
replaced with revised version Tue, 16 Dec 2008 18:22:54 GMT (1310kb,D)

Title: Dimer-dimer collisions at finite energies in two-component Fermi gases
Authors: J. P. D'Incao, Seth T. Rittenhouse, N. P. Mehta, Chris H. Greene
Categories: physics.atom-ph
Comments: 4.1 pages, 3 figures, revised text. Supplemental material provided: 2
   pages, 2 figures
\\ ( , 1310kb)
replaced with revised version Wed, 17 Dec 2008 20:48:32 GMT (241kb)

Title: Spin 3/2 fermions with attractive interactions in a one-dimensional
   optical lattice: phase diagrams, entanglement entropy, and the effect of the
Authors: G. Roux, S. Capponi, P. Lecheminant, P. Azaria
Categories: cond-mat.str-el
Comments: 15 pages, 21 figures
Journal-ref: Eur. Phys. J. B (2008)
DOI: 10.1140/epjb/e2008-00374-7
\\ ( , 241kb)
replaced with revised version Wed, 17 Dec 2008 04:49:41 GMT (142kb)

Title: Non-Abelian magnetic monopole in a Bose-Einstein condensate
Authors: Ville Pietil\"a and Mikko M\"ott\"onen
Categories: cond-mat.other cond-mat.mes-hall
Comments: 5 pages, 1 color figure; v2 modified according to referees'
   suggestions, some typos corrected
\\ ( , 142kb)
replaced with revised version Wed, 17 Dec 2008 13:24:53 GMT (410kb)

Title: On quenches in quantum many-body systems: the one-dimensional
   Bose-Hubbard model revisited
Authors: Guillaume Roux
Categories: cond-mat.str-el cond-mat.stat-mech
Comments: 4 pages, 4 figures
\\ ( , 410kb)
replaced with revised version Thu, 18 Dec 2008 16:25:38 GMT (13kb)

Title: Exact renormalisation group flow for ultracold Fermi gases in unitary
Authors: Boris Krippa
Categories: cond-mat.supr-con nucl-th
Comments: 11 pages, Revtex, misprints corrected, references and comments added
\\ ( , 13kb)
replaced with revised version Wed, 17 Dec 2008 23:13:08 GMT (113kb)

Title: Universality and Anomalous Mean-Field Breakdown of Symmetry-Breaking
   Transitions in A Coupled Two-Component Condensate
Authors: Chaohong Lee
Categories: cond-mat.mes-hall cond-mat.other
Comments: 4 pages, 3 eps figures, revised and improved version
\\ ( , 113kb)

Till next time,

Dr M. J. Davis,                      Associate Professor in Physics
School of Mathematics and Physics,   ph  : +61 7 334 69824
The University of Queensland,        fax : +61 7 336 51242
Brisbane, QLD 4072,        
Matt's arXiv selection: weekly summary of cold-atom papers from
Legal stuff: Unless stated otherwise, this e-mail represents only the
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Received on Wed Feb 25 2009 - 08:32:10 EST

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