# Matt's arXiv selection: week ending 25th May 2007.

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Wed, 6 Jun 2007 01:57:30 +1000 (EST)

The following message was sent to the matts_arxiv list by Matthew Davis <mdavis_at_physics.uq.edu.au>

Hi everyone,

The date in the title of my last email was incorrect - it should have read 18th
May 2007. So this email is the week ending 25 May, and has 29 new abstracts and
16 replacements.

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arXiv:0705.2658
Date: Fri, 18 May 2007 08:51:22 GMT (20kb)

Title: The Josephson effect in the BCS-BEC crossover
Authors: A. Spuntarelli, P. Pieri, G.C. Strinati
Categories: cond-mat.other cond-mat.supr-con
\\
We study the stationary Josephson effect for neutral fermions with a mutual
attractive interaction, that ranges from weak to strong coupling across the
BCS-BEC crossover, by solving numerically the Bogoliubov-de Gennes equations
for several types of barriers with an imposed current at zero temperature.
Implementing self-consistency in the calculation proves essential, especially
on the BEC side of the crossover where we recover a description of composite
bosons in terms of the Gross-Pitaevskii equation. We show that the maximum of
the Josephson current as a function of coupling occurs for all barriers at
about unitarity. In addition, in the limit of vanishing small barrier height,
this maximum approaches the value obtained by the Landau criterion which,
depending on the coupling, is determined by either pair-breaking or sound-mode
excitations. An experiment is suggested to identify the evolution of this
maximum value through the crossover.
\\ ( http://arxiv.org/abs/0705.2658 , 20kb)
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arXiv:0705.2684
Date: Fri, 18 May 2007 12:09:20 GMT (44kb)

Title: Superfluid to Mott-insulator transition in Bose-Hubbard models
Authors: Manuela Capello, Federico Becca, Michele Fabrizio, Sandro Sorella
Categories: cond-mat.str-el
Comments: 4 pages, 4 figures, based on cond-mat/0611306
\\
We study the superfluid-insulator transition in Bose-Hubbard models in one-,
two-, and three-dimensional cubic lattices by means of a recently proposed
variational wave function. In one dimension, the variational results agree with
the expected Berezinskii-Kosterlitz-Thouless scenario of the interaction-driven
Mott transition. In two and three dimensions, we find evidences that, across
the transition,most of the spectral weight is concentrated at high energies,
suggestive of pre-formed Mott-Hubbard side-bands. This result is compatible
with the experimental data by Stoferle et al.
[Phys. Rev. Lett. 92, 130403 (2004)].
\\ ( http://arxiv.org/abs/0705.2684 , 44kb)
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arXiv:0705.2732
Date: Fri, 18 May 2007 17:38:40 GMT (225kb)

Title: Quantum phases of bosons in double-well optical lattices
Authors: Ippei Danshita, James E. Williams, Carlos A. R. Sa de Melo, and
Charles W. Clark
Categories: cond-mat.other
\\
We study the superfluid to Mott insulator transition of bosons in a
two-legged ladder optical lattice, of a type accessible in current experiments
on double-well optical lattices. The zero-temperature phase diagram is mapped
out, with a focus on its dependence upon interchain hopping and the tilt
between double wells. We find that the unit-filling Mott phase exhibits a
non-monotonic behavior as a function of the tilt parameter, producing a
reentrant phase transition between Mott insulator and superfluid phases.
\\ ( http://arxiv.org/abs/0705.2732 , 225kb)
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arXiv:0705.2750
Date: Fri, 18 May 2007 18:09:06 GMT (21kb)

Title: Ultracold Thermalization of $^7$Li and $^{87}$Rb
Authors: C. Marzok, B. Deh, Ph.W. Courteille, and C. Zimmermann
Categories: cond-mat.other
Comments: 7 pages, 4 figures, 1 table
\\
We report on measurements of cross-species thermalization inside a
magnetically trapped spin-polarized mixture of $^{87}$Rb and $^7$Li atoms with
both atoms in their respective low field seeking magnetic substates
$|F=2,m_F=2\right>$. Measurement of the thermalization velocity in the
ultracold regime below $10 \mu$K allows for the derivation of the absolute
value of the pure triplet s-wave scattering length governing the interaction.
We find $|a_{7,87}|=(59\pm19) a_{\rm B}$. We propose to study both species in
the condensed regime to derive the sign of $a_{7,87}$. In this context, we
present numerical solutions to the coupled Gross-Pitaevskii equation based on
the hypothesis of a positive sign. According to the simulations, phase
separation of the Li and Rb $|2,2\right>$ clouds occurs along with a mean-field
stabilization allowing for larger atom numbers of condensed $^7$Li atoms before
collapse sets in. Observation of this mean-field stabilization would directly
fix the sign of $a_{7,87}$. We discuss our results in the light of this
proposal.
\\ ( http://arxiv.org/abs/0705.2750 , 21kb)
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arXiv:0705.2652
Date: Fri, 18 May 2007 08:30:13 GMT (188kb)

Title: Weak-Light Ultraslow Vector Optical Solitons via Electromagnetically
Induced Transparency
Authors: Chao Hang and Guoxiang Huang
Categories: physics.optics
\\
We propose a scheme to generate temporal vector optical solitons in a
transparency. We show that this scheme, which is fundamentally different from
the passive one by using optical fibers, is capable of achieving
distortion-free vector optical solitons with ultraslow propagating velocity
under very weak drive conditions. We demonstrate both analytically and
numerically that it is easy to realize Manakov temporal vector solitons by
actively manipulating the dispersion and self- and cross-phase modulation
effects of the system.
\\ ( http://arxiv.org/abs/0705.2652 , 188kb)
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arXiv:0705.2782
Date: Fri, 18 May 2007 21:28:49 GMT (484kb)

Title: Observation of a quenched moment of inertia in a rotating strongly
interacting Fermi gas
Authors: Bason Clancy, Le Luo, and John E. Thomas
Categories: cond-mat.other
\\
We make a model-independent measurement of the moment of inertia of a
rotating, expanding strongly-interacting Fermi gas. Quenching of the moment of
inertia is observed for energies both below and above the superfluid
transition. This shows that a strongly interacting Fermi gas with angular
momentum can support irrotational flow in both the superfluid and collisional
normal fluid regimes.
\\ ( http://arxiv.org/abs/0705.2782 , 484kb)
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arXiv:cond-mat/0512317
replaced with revised version Sat, 19 May 2007 16:41:41 GMT (33kb)

Title: The axial breathing mode in rapidly rotating Bose-Einstein condensates
and uncertainty of the rotation velocity
Authors: Gentaro Watanabe
Categories: cond-mat.mes-hall cond-mat.soft nucl-th
Comments: 5 pages, 2 figures; completely revised with new findings; title
changed. This paper is related to cond-mat/0506331
Report-no: NORDITA-2005-80
\\ ( http://arxiv.org/abs/cond-mat/0512317 , 33kb)
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arXiv:0705.2922
Date: Mon, 21 May 2007 06:40:00 GMT (650kb)

Title: I.C.E.: An Ultra-Cold Atom Source for Long-Baseline Interferometric
Inertial Sensors in Reduced Gravity
Authors: Ga\"el Varoquaux (LCFIO), Nassim Zahzam (ONERA), Oualid Chaibi
(SYRTE), Jean-Fran\c{c}ois Cl\'ement (LCFIO), Olivier Carraz (ONERA),
Jean-Philippe Brantut (LCFIO), Robert A. Nyman (LCFIO), Franck Pereira Dos
Santos (SYRTE), Linda Mondin (CNES DCT/SI/OP), Michel Rouz\'e (CNES
DCT/SI/OP), Yannick Bidel (ONERA), Alexandre Bresson (ONERA), Arnaud
Landragin (SYRTE), Philippe Bouyer (LCFIO)
Categories: physics.atom-ph
Proxy: ccsd hal-00147641
Journal-ref: Rencontres de Moriond Gravitational Waves and Experimental
Gravity, Italie (11/03/2007)
\\
The accuracy and precision of current atom-interferometric inertialsensors
rival state-of-the-art conventional devices using artifact-based test masses .
Atomic sensors are well suited for fundamental measurements of gravito-inertial
fields. The sensitivity required to test gravitational theories can be achieved
by extending the baseline of the interferometer. The I.C.E.
(Interf\'erom\'etrie Coh\'erente pour l'Espace) interferometer aims to achieve
long interrogation times in compact apparatus via reduced gravity. We have
tested a cold-atom source during airplane parabolic flights. We show that this
environment is compatible with free-fall interferometric measurements using up
to 4 second interrogation time. We present the next-generation apparatus using
degenerate gases for low release-velocity atomic sources in space-borne
experiments.
\\ ( http://arxiv.org/abs/0705.2922 , 650kb)
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arXiv:0705.2973
Date: Mon, 21 May 2007 13:17:23 GMT (255kb)

Title: Partially coherent matter wave and its evolution
Authors: Jun Chen and Qiang Lin
Categories: physics.atom-ph
\\
The evolution and propagation of a partially coherent matter wave (PCMW) is
investigated theoretically by the correlation function method. The ABCD matrix
formalism previously used for a fully coherent matter wave is extended to the
PCMW domain. A new ABCD law is derived, using a tensor method to describe the
evolution of a PCMW. An analytical solution of the first-order correlation
function is obtained that makes the propagation and evolution of a PCMW very
simple and clear. As an example, the propagation of a PCMW in a gravitational
field is calculated numerically.
\\ ( http://arxiv.org/abs/0705.2973 , 255kb)
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arXiv:0705.3036
Date: Mon, 21 May 2007 18:38:02 GMT (301kb)

Title: Feshbach resonances in ultracold K(39)
Authors: C. D'Errico, M. Zaccanti, M. Fattori, G. Roati, M. Inguscio, G.
Modugno, and A. Simoni
Categories: physics.atom-ph
\\
We discover several magnetic Feshbach resonances in collisions of ultracold
K(39) atoms, by studying atom losses and molecule formation. Accurate
determination of the magnetic-field resonance locations allows us to optimize a
quantum collision model for potassium isotopes. We employ the model to predict
the magnetic-field dependence of scattering lengths and of near-threshold
molecular levels. Our findings will be useful to plan future experiments on
ultracold potassium atoms and molecules.
\\ ( http://arxiv.org/abs/0705.3036 , 301kb)
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arXiv:0705.3093
Date: Tue, 22 May 2007 05:15:27 GMT (732kb)

Title: The Quantum de Laval Nozzle: stability and quantum dynamics of sonic
horizons in a toroidally trapped Bose gas containing a superflow
Authors: P. Jain, A. S. Bradley, C. W. Gardiner
Categories: cond-mat.other
\\
We study an experimentally realizable system containing stable black
hole-white hole acoustic horizons in toroidally trapped Bose-Einstein
condensates - the quantum de Laval nozzle. We numerically obtain stationary
flow configurations and assess their stability using Bogoliubov theory, finding
both in hydrodynamic and non-hydrodynamic regimes there exist dynamically
unstable regions associated with the creation of positive and negative energy
quasiparticle pairs in analogy with the gravitational Hawking effect. The
dynamical instability takes the form of a two mode squeezing interaction
between resonant pairs of Bogoliubov modes. We study the evolution of
dynamically unstable flows using the truncated Wigner method, which confirms
the two mode squeezed state picture of the analogue Hawking effect for low
winding number.
\\ ( http://arxiv.org/abs/0705.3093 , 732kb)
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arXiv:0705.3205
Date: Tue, 22 May 2007 16:03:54 GMT (93kb)

Title: Quantum dynamics of two bosons in an anharmonic trap: Collective vs
internal excitations
Authors: Christian Matthies, Sascha Z\"ollner, Hans-Dieter Meyer, and Peter
Schmelcher
Categories: cond-mat.other
\\
This work deals with the effects of an anharmonic trap on an interacting
two-boson system in one dimension. Our primary focus is on the role of the
induced coupling between the center of mass and the relative motion as both
anharmonicity and the (repulsive) interaction strength are varied. The ground
state reveals a strong localization in the relative coordinate, counteracting
the tendency to fragment for stronger repulsion. To explore the quantum
dynamics, we study the system's response upon (i) exciting the harmonic ground
state by continuously switching on an additional anharmonicity, and (ii)
displacing the center of mass, this way triggering collective oscillations. The
interplay between collective and internal dynamics materializes in the collapse
of oscillations, which are explained in terms of few-mode models.
\\ ( http://arxiv.org/abs/0705.3205 , 93kb)
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arXiv:0705.3155
Date: Tue, 22 May 2007 13:02:42 GMT (599kb)

Title: Observation of Topological and Parity-dependent Phase of $m=0$ Spin
States
Authors: Koji Usami and Mikio Kozuma
Categories: quant-ph
\\
A Ramsey interrogation scheme was used to measure the phase shift of
laser-cooled $^{87}$Rb clock-transition pseudospins arising as a result of a
reversal of a bias magnetic field, i.e., $\textbf{B} \to -\textbf{B}$, during
the interrogation. While no phase shift occurred when the reversal was sudden,
the Ramsey fringes were shifted by a factor of $\pi$ when the reversal was
adiabatic. We thus verified the prediction that the spin states $|F,m=0 >$
acquire a purely topological and parity-dependent phase factor of $(-1)^{F}$ as
a result of $\textbf{B} \to -\textbf{B}$.
\\ ( http://arxiv.org/abs/0705.3155 , 599kb)
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arXiv:0705.3234
Date: Tue, 22 May 2007 19:02:10 GMT (867kb)

Title: Development of an apparatus for cooling 6Li-87Rb Fermi-Bose mixtures in
a light-assisted magnetic trap
Authors: M. Brown-Hayes, Q. Wei, W.-J. Kim, and R. Onofrio
Categories: physics.atom-ph physics.optics
Comments: Presented at LPHYS'06, 8 figures
Journal-ref: Laser Physics 17 (2007) pp. 514-522
\\
We describe an experimental setup designed to produce ultracold trapped gas
clouds of fermionic 6Li and bosonic 87Rb. This combination of alkali metals has
the potential to reach deeper Fermi degeneracy with respect to other mixtures
since it allows for improved heat capacity matching which optimizes sympathetic
cooling efficiency. Atomic beams of the two species are independently produced
and then decelerated by Zeeman slowers. The slowed atoms are collected into a
magneto-optical trap and then transferred into a quadrupole magnetic trap. An
ultracold Fermi gas with temperature in the 10^-3 T_F range should be
attainable through selective confinement of the two species via a properly
detuned laser beam focused in the center of the magnetic trap.
\\ ( http://arxiv.org/abs/0705.3234 , 867kb)
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arXiv:0705.3298
Date: Wed, 23 May 2007 07:25:19 GMT (142kb)

Title: Bogoliubov spectrum of a cigar shaped Fermi superfluid in an optical
lattice at the BEC-BCS crossover
Authors: Aranya B Bhattacherjee
Categories: cond-mat.stat-mech
\\
We study the Bogoliubov spectrum of an elongated Fermi superfluid confined in
an one-dimensional superfluid along the Bose-Einstein-condensate
(BEC)-Bardeen-Cooper-Schrieffer (BCS) crossover. We derive analytic expressions
for the sound velocity, effective mass and the Bogoliubov excitation spectrum
of the axial quasiparticles long the crossover based on the hydrodynamic
theory. Our investigation reveal interesting signatures of BEC-BCS crossover in
an optical lattice which deserve experimental investigation.
\\ ( http://arxiv.org/abs/0705.3298 , 142kb)
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arXiv:0705.3341
Date: Wed, 23 May 2007 19:22:48 GMT (450kb)

Title: Hall effects in Bose-Einstein condensates in a rotating optical lattice
Authors: Rajiv Bhat, M. Kraemer, J. Cooper, M. J. Holland
Categories: cond-mat.mes-hall cond-mat.other
\\
Using the Kubo formalism, we demonstrate fractional quantum Hall features in
a rotating Bose-Einstein condensate in a co-rotating two-dimensional optical
lattice. The co-rotating lattice and trap potential allow for an effective
magnetic field and compensation of the centrifugal potential. Fractional
quantum Hall features are seen for the single-particle system and for few
strongly interacting many-particle systems.
\\ ( http://arxiv.org/abs/0705.3341 , 450kb)
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arXiv:0705.3361
Date: Wed, 23 May 2007 12:33:37 GMT (636kb)

Title: Imbalanced Superfluid Phase of a Trapped Fermi Gas in the BCS-BEC
Crossover Regime
Authors: T. Mizushima, M. Ichioka, K. Machida
Categories: cond-mat.supr-con
\\
We theoretically investigate the ground state of trapped neutral fermions
with population imbalance in the BCS-BEC crossover regime. Based on the
single-channel Hamiltonian, we perform fully numerical calculations of the
Bogoliubov-de Gennes equation coupled with the regularized gap and number
equations. The zero temperature phase diagram in the crossover regime is
presented, where the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) pairing state
governs the weak coupling BCS region of a resonance. It is found that the FFLO
oscillation vanishes in the BEC side, in which the system under population
imbalance turns into the phase separation (PS) between locally binding
superfluid and fully polarized spin domains. We also demonstrate the numerical
calculations with a large particle number O(10^5) comparable with the recent
experiments. The resulting density profile on a resonance yields the PS which
is in good agreement with the recent experiments, while there exists the FFLO
modulation in the pairing field. It is also proposed that the most favorable
situation for the detection of the FFLO oscillation is in the vicinity of the
critical population imbalance in the weak coupling BCS regime, where the
oscillation periodicity becomes much larger than the interparticle spacing.
Finally, we analyze the radio-frequency (RF) spectroscopy in the imbalanced
system. The clear difference of the RF spectroscopy between BCS and BEC sides
reveals the structure on the pairing field and local magnetization''.
\\ ( http://arxiv.org/abs/0705.3361 , 636kb)
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arXiv:0705.3376
Date: Wed, 23 May 2007 13:51:46 GMT (214kb)

Title: Gaussian number-squeezed states for sub-shot-noise interferometery in
double-well Bose-Einstein condensates
Authors: Y. P. Huang and M. G. Moore
Categories: quant-ph
\\
We show that a Mach-Zender interferometer with a gaussian number-squeezed
input state can exhibit sub-shot-noise phase resolution over a large range of
measured phase-shifts in a single measurement. In contrast, previously studied
input states are shown to degrade quickly to worse than shot-noise when a
non-zero phase-shift is measured. This interferometer can be implemented in a
double-well Bose-Einstein condensate system, and the gaussian squeezed states
can obtained via adiabatic manipulation of the ground state in the presence of
repulsive atomic interactions. From Bayesian analysis, we find that the
phase-estimation uncertainty scales as 1/N at zero phase, and crosses over
smoothly to the shot-noise limit $1/\sqrt{N}$ as the phase approaches
$\pm\pi/2$.
\\ ( http://arxiv.org/abs/0705.3376 , 214kb)
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arXiv:0705.3268
Date: Wed, 23 May 2007 00:09:22 GMT (216kb)

Title: Atomtronic circuits of diodes and transistors
Authors: R. A. Pepino, J. Cooper, D. Z. Anderson & M. J. Holland
Categories: physics.atom-ph
\\
In this letter, we illustrate that open quantum systems composed of neutral,
ultracold atomic gases trapped in optical lattices can exhibit analogous
behavior to semiconductor electronic circuits. A precise, physically-attainable
correspondence is demonstrated and the experimental parameters needed to
realize the behavior of semiconductor diodes and transistors are presented. Our
analysis follows from our formulation of a modified master equation approach to
this general class of open quantum systems.
\\ ( http://arxiv.org/abs/0705.3268 , 216kb)
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arXiv:0705.3302
Date: Wed, 23 May 2007 08:28:48 GMT (63kb)

Title: Modeling many-particle mechanical effects of an interacting Rydberg gas
Authors: Thomas Amthor, Markus Reetz-Lamour, Christian Giese, and Matthias
Weidem\"{u}ller
Categories: physics.atom-ph
\\
In a recent work [Phys. Rev. Lett. 98, 023004 (2007)] we have investigated
the influence of attractive van der Waals interaction on the pair distribution
and Penning ionization dynamics of ultracold Rydberg gases. Here we extend this
description to atoms initially prepared in Rydberg states exhibiting repulsive
interaction. We present calculations based on a Monte Carlo algorithm to
simulate the dynamics of many atoms under the influence of both repulsive and
attractive longrange interatomic forces. Redistribution to nearby states
induced by black body radiation is taken into account, changing the effective
interaction potentials. The model agrees with experimental observations, where
the ionization rate is found to increase when the excitation laser is
blue-detuned from the atomic resonance.
\\ ( http://arxiv.org/abs/0705.3302 , 63kb)
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arXiv:0705.3416
Date: Wed, 23 May 2007 16:44:50 GMT (96kb)

Title: Electron Temperature Evolution in Expanding Ultracold Neutral Plasmas
Authors: P. Gupta, S. Laha, C. E. Simien, H. Gao, J. Castro, T. Pohl and T. C.
Killian
Categories: physics.atom-ph physics.plasm-ph
\\
We have used the free expansion of ultracold neutral plasmas as a
time-resolved probe of electron temperature. A combination of experimental
measurements of the ion expansion velocity and numerical simulations
characterize the crossover from an elastic-collision regime at low initial
Gamma_e, which is dominated by adiabatic cooling of the electrons, to the
regime of high Gamma_e in which inelastic processes drastically heat the
electrons. We identify the time scales and relative contributions of various
processes, and experimentally show the importance of radiative decay and
disorder-induced electron heating for the first time in ultracold neutral
plasmas.
\\ ( http://arxiv.org/abs/0705.3416 , 96kb)
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arXiv:0705.3442
Date: Wed, 23 May 2007 18:49:18 GMT (663kb,D)

Title: Mitigation of loss within a molecular Stark decelerator
Authors: Brian C. Sawyer, Benjamin K. Stuhl, Benjamin L. Lev, Eric R. Hudson,
and Jun Ye
Categories: physics.atom-ph physics.atm-clus
\\
The transverse motion inside a Stark decelerator plays a large role in the
total efficiency of deceleration. We differentiate between two separate regimes
of molecule loss during the slowing process. The first mechanism involves
distributed loss due to coupling of transverse and longitudinal motion, while
the second is a result of the rapid decrease of the molecular velocity within
the final few stages. In this work, we describe these effects and present means
for overcoming them. Solutions based on modified switching time sequences with
the existing decelerator geometry lead to a large gain of stable molecules in
the intermediate velocity regime, but fail to address the loss at very low
final velocities. We propose a new decelerator design, the quadrupole-guiding
decelerator, which eliminates distributed loss due to transverse/longitudinal
couplings throughout the slowing process and also exhibits gain over normal
deceleration to the lowest velocities.
\\ ( http://arxiv.org/abs/0705.3442 , 663kb)
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arXiv:0705.3454
Date: Wed, 23 May 2007 23:33:10 GMT (551kb)

Title: Engineering fidelity echoes in Bose-Hubbard Hamiltonians
Authors: J.D. Bodyfelt, M. Hiller and T. Kottos
Categories: cond-mat.other
Comments: 6 pages, use epl2.cls class, 5 figures Cross reference with nlin,
quant-phys
Journal-ref: EPL 78 (2007) 50003
DOI: 10.1209/0295-5075/78/50003
\\
We analyze the fidelity decay for a system of interacting bosons described by
a Bose-Hubbard Hamiltonian. We find echoes associated with "non-universal"
structures that dominate the energy landscape of the perturbation operator.
Despite their classical origin, these echoes persist deep into the quantum
(perturbative) regime and can be described by an improved random matrix
modeling. In the opposite limit of strong perturbations (and high enough
energies), classical considerations reveal the importance of self-trapping
phenomena in the echo efficiency.
\\ ( http://arxiv.org/abs/0705.3454 , 551kb)
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arXiv:0705.3569
Date: Thu, 24 May 2007 16:31:53 GMT (15kb)

Title: A note on the spin-1/2 XXZ chain concerning its relation to the Bose gas
Authors: Alexander Seel, Tanaya Bhattacharyya, Frank G\"{o}hmann, Andreas
Kl\"{u}mper
Categories: cond-mat.stat-mech
\\
By considering the one-particle and two-particle scattering data of the
spin-1/2 Heisenberg chain at T=0 we derive a continuum limit relating the spin
chain to the 1D Bose gas. Applying this limit to the quantum transfer matrix
approach of the Heisenberg chain we obtain expressions for the correlation
functions of the Bose gas at arbitrary temperatures.
\\ ( http://arxiv.org/abs/0705.3569 , 15kb)
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arXiv:0705.3456
Date: Thu, 24 May 2007 18:50:48 GMT (402kb)

Title: Unifying variational methods for simulating quantum many-body systems
Authors: Christopher M. Dawson, Jens Eisert, Tobias J. Osborne
Categories: quant-ph
\\
We introduce a unified formulation of variational methods for simulating
ground state properties of quantum many-body systems. The key feature is a
novel variational method over quantum circuits via infinitesimal unitary
transformations, inspired by flow equation methods. This gives rise to a
unifying picture of several existing variational techniques for simulating
strongly correlated systems: variational classes are represented as efficiently
contractible unitary networks, including, the matrix-product states of density
matrix renormalization (DMRG), multiscale entanglement renormalization (MERA)
states, weighted graph states, quantum cellular automata, and others. In
particular, this provides a tool for varying over classes of states, such as
MERA, for which so far no efficient way of variation is known, including
two-dimensional systems. The scheme is flexible when it comes to hybridizing
existing methods or formulating new ones. We demonstrate the functioning of the
formalism by a numerical implementation.
\\ ( http://arxiv.org/abs/0705.3456 , 402kb)
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arXiv:0705.3477
Date: Wed, 23 May 2007 22:21:40 GMT (129kb)

Title: Vacuum Fluctuations induced Entanglement between Two Mesoscopic Systems
Authors: H. T. Ng and K. Burnett
Categories: quant-ph
\\
We study the dynamics of a pair of molecular ensembles trapped inside a
superconducting resonator through which they are strongly coupled via a
microwave field mode. We find that entanglement can be generated via vacuum
fluctuations'' even when the molecules and cavity field are initially prepared
in their ground state. This entanglement is created in a relatively short time
and without the need for further manipulation of the system. It does,
therefore, provide a convenient scheme to entangle two mesoscopic systems, and
may well be useful quantum information processing.
\\ ( http://arxiv.org/abs/0705.3477 , 129kb)
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arXiv:0705.3491
Date: Thu, 24 May 2007 01:13:23 GMT (9kb)

Title: Opposite sign correlations in fermion or boson gases
Authors: Alex D. Gottlieb, Thorsten Schumm
Categories: quant-ph
\\
We investigate pair correlations in trapped fermion and boson gases as a
means to probe the quantum states producing the density fluctuations. We point
out that "opposite sign correlations" (meaning pair correlations that are
positive for fermions and negative for bosons) unambiguously indicate that the
quantum many-particle state cannot be "free." In particular, a system of
fermions that exhibits positive pair correlations cannot be described by any
Slater determinant wavefunction. This insight may help one to interpret results
of current experiments on ultracold atomic gases.
\\ ( http://arxiv.org/abs/0705.3491 , 9kb)
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arXiv:0705.3506
Date: Thu, 24 May 2007 04:48:45 GMT (145kb,D)

Title: Entangled-State Cycles of Atomic Collective-Spin States
Authors: A. Chia and A. S. Parkins
Categories: quant-ph
\\
We study quantum trajectories of collective atomic spin states of $N$
effective two-level atoms driven with laser and cavity fields. We show that
interesting entangled-state cycles'' arise probabilistically when the (Raman)
transition rates between the two atomic levels are set equal. For odd (even)
$N$, there are $(N+1)/2$ ($N/2$) possible cycles. During each cycle the
$N$-qubit state switches, with each cavity photon emission, between the states
$(|N/2,m>\pm |N/2,-m>)/\sqrt{2}$, where $|N/2,m>$ is a Dicke state in a rotated
collective basis. The quantum number $m$ ($>0$), which distinguishes the
particular cycle, is determined by the photon counting record and varies
randomly from one trajectory to the next. For even $N$ it is also possible,
under the same conditions, to prepare probabilistically (but in steady state)
the Dicke state $|N/2,0>$, i.e., an $N$-qubit state with $N/2$ excitations,
which is of particular interest in the context of multipartite entanglement.
\\ ( http://arxiv.org/abs/0705.3506 , 145kb)
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arXiv:0705.3639
Date: Thu, 24 May 2007 19:06:21 GMT (510kb,D)

Title: Prospects for the cavity-assisted laser cooling of molecules
Authors: Benjamin L. Lev, Andras Vukics, Eric R. Hudson, Brian C. Sawyer, Peter
Domokos, Helmut Ritsch, and Jun Ye
Categories: quant-ph
\\
Cooling of molecules via free-space dissipative scattering of photons is
thought not to be practicable due to the inherently large number of Raman loss
channels available to molecules and the prohibitive expense of building
multiple repumping laser systems. The use of an optical cavity to enhance
coherent Rayleigh scattering into a decaying cavity mode has been suggested as
a potential method to mitigate Raman loss, thereby enabling the laser cooling
of molecules to ultracold temperatures. We discuss the possibility of
cavity-assisted laser cooling particles without closed transitions, identify
conditions necessary to achieve efficient cooling, and suggest solutions given
experimental constraints. Specifically, it is shown that cooperativities much
greater than unity are required for cooling without loss, and that this could
be achieved via the superradiant scattering associated with intracavity
self-localization of the molecules. Particular emphasis is given to the polar
hydroxyl radical (OH), cold samples of which are readily obtained from Stark
deceleration.
\\ ( http://arxiv.org/abs/0705.3639 , 510kb)
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The replacments:

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arXiv:cond-mat/0205210
replaced with revised version Fri, 18 May 2007 15:32:40 GMT (25kb)

Title: Stability of the two-dimensional Bose gases in the resonant regime
Authors: Ludovic Pricoupenko and Maxim Olshanii
Categories: cond-mat
Comments: 6 pages, latex, 2 figures
Journal-ref: J. Phys. B: At. Mol. Opt. Phys. 40 (2007) 2065-2074
DOI: 10.1088/0953-4075/40/11/009
\\ ( http://arxiv.org/abs/cond-mat/0205210 , 25kb)
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\\
arXiv:cond-mat/0506264
replaced with revised version Fri, 18 May 2007 02:03:36 GMT (45kb)

Title: Exact results for the 1D interacting Fermi gas with arbitrary
polarization
Authors: M.T. Batchelor, M. Bortz, X.W. Guan and N. Oelkers
Categories: cond-mat.str-el cond-mat.stat-mech
Comments: 7 pages, 3 figures, final published version without the discussion of
harmonic trapping (to be taken up elsewhere). The effect of a magnetic-like
field term on pairing and phase transtions has been discussed via the TBA
approach in cond-mat/0702191
Journal-ref: J. Phys. Conf. Ser. 42 (2006) 5
DOI: 10.1088/1742-6596/42/1/002
\\ ( http://arxiv.org/abs/cond-mat/0506264 , 45kb)
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arXiv:cond-mat/0701058
replaced with revised version Fri, 18 May 2007 15:14:57 GMT (9kb)

Title: Decoherence Dynamics in Low-Dimensional Cold Atom Interferometers
Authors: A.A. Burkov, M.D. Lukin, Eugene Demler
Categories: cond-mat.supr-con cond-mat.str-el
Journal-ref: Phys. Rev. Lett. 98, 200404 (2007)
DOI: 10.1103/PhysRevLett.98.200404
\\ ( http://arxiv.org/abs/cond-mat/0701058 , 9kb)
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arXiv:0704.1995
replaced with revised version Sat, 19 May 2007 08:40:29 GMT (85kb)

Title: Coherent dynamics of domain formation in the Bose Ferromagnet
Authors: Qiang Gu, Haibo Qiu
Categories: cond-mat.other cond-mat.stat-mech
Journal-ref: Phys. Rev. Lett. 98, 200401 (2007)
\\ ( http://arxiv.org/abs/0704.1995 , 85kb)
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arXiv:cond-mat/0608585
replaced with revised version Sat, 19 May 2007 16:47:29 GMT (936kb)

Title: Long Phase Coherence Time and Number Squeezing of two Bose-Einstein
Condensates on an Atom Chip
Authors: G.-B. Jo, Y. Shin, S. Will, T. A. Pasquini, M. Saba, W. Ketterle, D.
E. Pritchard, M. Vengalattore, and M. Prentiss
Categories: cond-mat.other
Journal-ref: Phy. Rev. Lett. 98, 030407 (2007)
DOI: 10.1103/PhysRevLett.98.030407
\\ ( http://arxiv.org/abs/cond-mat/0608585 , 936kb)
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arXiv:cond-mat/0703006
replaced with revised version Sat, 19 May 2007 16:34:45 GMT (869kb)

Title: Phase Sensitive Recombination of Two Bose-Einstein Condensates on an
Atom Chip
Authors: G.-B. Jo, J.-H. Choi, C.A. Christensen, T.A. Pasquini, Y.-R. Lee, W.
Ketterle, and D.E. Pritchard
Categories: cond-mat.other
Journal-ref: Phys. Rev. Lett. 98, 180401 (2007)
DOI: 10.1103/PhysRevLett.98.180401
\\ ( http://arxiv.org/abs/cond-mat/0703006 , 869kb)
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arXiv:cond-mat/0601148
replaced with revised version Tue, 22 May 2007 02:30:31 GMT (56kb)

Title: Surface Energy in Cold Asymmetrical Fermion Superfluids
Authors: Heron Caldas
Categories: cond-mat.supr-con astro-ph cond-mat.str-el hep-ph nucl-th
Comments: 12 pages, 2 figures, expanded version, typos corrected, references
\\ ( http://arxiv.org/abs/cond-mat/0601148 , 56kb)
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arXiv:cond-mat/0703805
replaced with revised version Tue, 22 May 2007 04:13:57 GMT (87kb)

Title: Multicomponent Bright Solitons in F = 2 Spinor Bose-Einstein Condensates
Authors: Masaru Uchiyama, Jun'ichi Ieda, Miki Wadati
Categories: cond-mat.other nlin.SI
\\ ( http://arxiv.org/abs/cond-mat/0703805 , 87kb)
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arXiv:cond-mat/0412269
replaced with revised version Wed, 23 May 2007 12:20:26 GMT (26kb)

Title: Density correlations in ultracold atomic Fermi gases
Authors: W. Belzig, C. Schroll, and C. Bruder
Categories: cond-mat.supr-con cond-mat.mes-hall
Comments: 4 pages, 4 figures. To appear in Phys. Rev. A. New calculation of the
bin statistics of a free Bose gas; updated and extended bibliography
\\ ( http://arxiv.org/abs/cond-mat/0412269 , 26kb)
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arXiv:cond-mat/0601148
replaced with revised version Tue, 22 May 2007 20:51:36 GMT (56kb)

Title: Surface Energy in Cold Asymmetrical Fermion Superfluids
Authors: Heron Caldas
Categories: cond-mat.supr-con astro-ph cond-mat.str-el hep-ph nucl-th
Comments: 12 pages, 2 figures, expanded version, typos corrected, references
\\ ( http://arxiv.org/abs/cond-mat/0601148 , 56kb)
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arXiv:cond-mat/0612498
replaced with revised version Wed, 23 May 2007 10:13:20 GMT (90kb)

Title: Metastable states of a gas of dipolar bosons in a 2D optical lattice
Authors: C. Menotti, C. Trefzger, and M. Lewenstein
Categories: cond-mat.other cond-mat.dis-nn
references. 4 pages, 4 figures, to appear in Phys. Rev. Lett
\\ ( http://arxiv.org/abs/cond-mat/0612498 , 90kb)
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arXiv:cond-mat/0612670
replaced with revised version Wed, 23 May 2007 18:52:38 GMT (29kb)

Title: Anderson Localization of Expanding Bose-Einstein Condensates in Random
Potentials
Authors: Laurent Sanchez-Palencia (LCFIO), David Cl\'ement (LCFIO), Pierre
Lugan (LCFIO), Philippe Bouyer (LCFIO), Georgy V. Shlyapnikov (LPTMS), Alain
Aspect (LCFIO)
Categories: cond-mat.other
Comments: published versioon (no significant change compared to last version)
Journal-ref: Physical Review Letters 98 (2007) 210401
DOI: 10.1103/PhysRevLett.98.210401
\\ ( http://arxiv.org/abs/cond-mat/0612670 , 29kb)
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arXiv:quant-ph/0609119
replaced with revised version Tue, 22 May 2007 22:05:01 GMT (568kb)

Title: Ultracold Bosons in a Tilted Multi-level Double-Well Potential
Authors: D. R. Dounas-Frazer, A. M. Hermundstad, and L. D. Carr
Categories: quant-ph cond-mat.other
\\ ( http://arxiv.org/abs/quant-ph/0609119 , 568kb)
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arXiv:cond-mat/0604424
replaced with revised version Thu, 24 May 2007 19:27:15 GMT (121kb)

Title: Non-BCS superfluidity in trapped ultracold Fermi gases
Authors: L. M. Jensen, J. Kinnunen, and P. Torma
Categories: cond-mat.str-el cond-mat.other
Comments: Extended and revised, 13 pages, 13 figures
\\ ( http://arxiv.org/abs/cond-mat/0604424 , 121kb)
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arXiv:cond-mat/0612302
replaced with revised version Thu, 24 May 2007 18:00:10 GMT (94kb)

Title: Edge Transport in 2D Cold Atom Optical Lattices
Authors: V.W. Scarola and S. Das Sarma
Categories: cond-mat.other quant-ph
Journal-ref: Phys. Rev. Lett. 98, 210403 (2007)
\\ ( http://arxiv.org/abs/cond-mat/0612302 , 94kb)
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arXiv:physics/0612143
replaced with revised version Thu, 24 May 2007 11:39:56 GMT (138kb)

Title: Dynamical interferences to probe short-pulse photoassociation of Rb
atoms and stabilization of Rb_2 dimers
Authors: Jordi Mur-Petit, Eliane Luc-Koenig, Francoise Masnou-Seeuws
Categories: physics.atom-ph cond-mat.other quant-ph
Comments: 4 pages, 5 figures. v2: major changes in introduction, discussion
clarified. v3: minor corrections, version accepted for publication in Phys.
Rev. A (Rapid Comm.)
\\ ( http://arxiv.org/abs/physics/0612143 , 138kb)
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Till next time,
Matt.

--
=========================================================================
Dr M. J. Davis,               Senior Lecturer in Physics
School of Physical Sciences,  email: mdavis_at_physics.uq.edu.au
University of Queensland,     ph   : +61 7 334 69824
Brisbane, QLD 4072,           fax  : +61 7 336 51242
Australia.                    http://www.physics.uq.edu.au/people/mdavis/
=========================================================================
Matt's arXiv selection: weekly summary of cold-atom papers from arXiv.org
http://www.physics.uq.edu.au/people/mdavis/matts_arXiv/
=========================================================================
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Received on Wed Jun 06 2007 - 01:57:30 EST

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