# Matt's arXiv selection: week ending 14th September 2007.

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Sun, 7 Oct 2007 00:55:00 +1000 (EST)

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

Hi everyone,

This week I have chosen a massive 37 new preprints, and 6 replacements. You've
been busy bees in September it seems.

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arXiv:0709.0964
Date: Thu, 6 Sep 2007 22:20:41 GMT (991kb)

Title: Computing quantum phase transitions
Authors: Thomas Vojta
Categories: cond-mat.stat-mech cond-mat.str-el
Comments: 99 pages, 15 figures, submitted to Reviews in Computational Chemistry
\\
emphasizing similarities with and differences to classical thermal transitions.
After pointing out the computational challenges posed by quantum phase
transitions, a number of successful computational approaches is discussed. The
focus is on classical and quantum Monte Carlo methods, with the former being
based on the quantum-to classical mapping while the latter directly attack the
quantum problem. These methods are illustrated by several examples of quantum
phase transitions in clean and disordered systems.
\\ ( http://arxiv.org/abs/0709.0964 , 991kb)
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arXiv:0709.0985
Date: Fri, 7 Sep 2007 02:41:29 GMT (335kb,D)

Title: Matterwave Transport Without Transit
Authors: M. Rab, J. H. Cole, N. G. Parker, A. D. Greentree, L. C. L. Hollenberg
and A. M. Martin
Categories: cond-mat.other
\\
Classically it is impossible to have transport without transit, i.e., if the
points one, two and three lie sequentially along a path then an object moving
from one to three must, at some point in time, be located at two. However, for
a quantum particle in a three-well system it is possible to transport the
particle between wells one and three such that the probability of finding it at
any time in the classically accessible state in well two is negligible. We
consider theoretically the analogous scenario for a Bose-Einstein condensate
confined within a three well system. In particular, we predict the adiabatic
transportation of an interacting Bose-Einstein condensate of 2000 Li atoms from
well one to well three without transiting the allowed intermediate region. To
an observer of this macroscopic quantum effect it would appear that, over a
timescale of the order of one second, the condensate had transported, but not
transited, a macroscopic distance of 20 microns between wells one and three.
\\ ( http://arxiv.org/abs/0709.0985 , 335kb)
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arXiv:0709.1017
Date: Fri, 7 Sep 2007 08:14:25 GMT (167kb)

Title: A multibeam atom laser: coherent atom beam splitting from a single far
detuned laser
Authors: J. Dugu\'e, G. Dennis, M. Jeppesen, M. T. Johnsson, C. Figl, N. P.
Robins and J. D. Close
Categories: cond-mat.other
\\
We report the experimental realisation of a multibeam atom laser. A single
continuous atom laser is outcoupled from a Bose-Einstein condensate (BEC) via
an optical Raman transition. The atom laser is subsequently split into up to
five atomic beams with slightly different momenta, resulting in multiple,
nearly co-propagating, coherent beams which could be of use in interferometric
experiments. The splitting process itself is a novel realization of Bragg
diffraction, driven by each of the optical Raman laser beams independently.
This presents a significantly simpler implementation of an atomic beam
splitter, one of the main elements of coherent atom optics.
\\ ( http://arxiv.org/abs/0709.1017 , 167kb)
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arXiv:0709.1042
Date: Fri, 7 Sep 2007 10:33:26 GMT (570kb)

Title: Quantized vortices in atomic Bose-Einstein condensates
Authors: Kenichi Kasamatsu, Makoto Tsubota
Categories: cond-mat.other cond-mat.mes-hall
Comments: 49 pages, 12 figures, review article
\\
In this review, we give an overview of the experimental and theoretical
advances in the physics of quantized vortices in dilute atomic-gas
Bose--Einstein condensates in a trapping potential, especially focusing on
experimental research activities and their theoretical interpretations. Making
good use of the atom optical technique, the experiments have revealed many
novel structural and dynamic properties of quantized vortices by directly
visualizing vortex cores from an image of the density profiles. These results
lead to a deep understanding of superfluid hydrodynamics of such systems.
Typically, vortices are stabilized by a rotating potential created by a laser
beam, magnetic field, and thermal gas. Finite size effects and inhomogeneity of
the system, originating from the confinement by the trapping potential, yield
unique vortex dynamics coupled with the collective excitations of the
condensate. Measuring the frequencies of the collective modes is an accurate
tool for clarifying the character of the vortex state. The topics included in
this review are the mechanism of vortex formation, equilibrium properties, and
dynamics of a single vortex and those of a vortex lattice in a rapidly rotating
condensate.
\\ ( http://arxiv.org/abs/0709.1042 , 570kb)
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arXiv:0709.1120
Date: Fri, 7 Sep 2007 17:09:58 GMT (16kb)

Title: Quasi-one-dimensional polarized Fermi superfluids
Authors: Meera M. Parish, Stefan K. Baur, Erich J. Mueller, David A. Huse
Categories: cond-mat.other cond-mat.supr-con
\\
We calculate the zero temperature phase diagram of a polarized two-component
Fermi gas in an array of weakly-coupled parallel one-dimensional (1D) 'tubes'
produced by a two-dimensional optical lattice. Increasing the lattice strength
drives a crossover from three-dimensional (3D) to 1D behavior, stabilizing the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) modulated superfluid phase. We argue
that the most promising regime for observing the FFLO phase is in the quasi-1D
regime, where the atomic motion is largely one-dimensional but there is weak
tunneling in the other directions that stabilizes long range order. In the FFLO
phase, we describe a phase transition where the quasiparticle spectrum changes
from gapless near the 3D regime to gapped in quasi-1D.
\\ ( http://arxiv.org/abs/0709.1120 , 16kb)
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arXiv:0709.1293
Date: Mon, 10 Sep 2007 01:17:15 GMT (49kb,D)

Title: Quantum corrections to the properties of an ideal Bose gas at T<T_C
Authors: E. Kovalchuk and R. Kobes
Categories: cond-mat.other
Comments: 12 pages, 13 figures, uses revtex4
\\
We consider a homogeneous equilibrium non-ideal Bose gas at nonzero
temperature below the critical temperature $T_C$ in the framework of finite
temperature field theory. Quantum corrections up to the second order are
calculated, and are shown to be important in consideration of quantities such
as the specific heat and critical exponent.
\\ ( http://arxiv.org/abs/0709.1293 , 49kb)
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arXiv:0709.1311
Date: Mon, 10 Sep 2007 05:17:09 GMT (5kb)

Title: Higher order terms in the condensate fraction of a homogeneous and
dilute Bose gas
Authors: Sang-Hoon Kim
Categories: cond-mat.stat-mech
\\
The condensate fraction of a homogeneous and dilute Bose gas is expanded as a
power series of $\sqrt{n a^3}$ as $N_0/N = 1 -c_1 (n a^3)^{1/2} -c_2 (n a^3) - \hdots.$ The coefficient $c_1$ is well-known as $8/3 \sqrt{\pi}$, but the
others are unknown yet. We analytically obtained the coefficient $c_2$ as
$3(\pi - 8/3)$ using a double canonical transformation method.
\\ ( http://arxiv.org/abs/0709.1311 , 5kb)
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arXiv:0709.1325
Date: Mon, 10 Sep 2007 08:42:23 GMT (38kb)

Title: Dynamics of interacting particle systems: stochastic process and field
theory
Authors: Alexandre lefevre and Giulio Biroli
Categories: cond-mat.stat-mech
Comments: Article for the special issue of J Stat Mech on "Dynamics of Non
Equilibrium Systems"
Journal-ref: J. Stat. Mech. (2007) P07024
DOI: 10.1088/1742-5468/2007/07/P07024
\\
We present an approach to the dynamics of interacting particle systems, which
allows to derive path integral formulas from purely stochastic considerations.
We show that the resulting field theory is a dual version of the standard
theory of Doi and Peliti. This clarify both the origin of the Cole-Hopf map
between the two approaches and the occurence of imaginary noises in effective
Langevin equations for reaction-diffusion systems. The advantage of our
approach is that it focuses directly on the density field. We show some
applications, in particular on the Zero Range Process, hydrodynamic limits and
large deviation functional.
\\ ( http://arxiv.org/abs/0709.1325 , 38kb)
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arXiv:0709.1362
Date: Mon, 10 Sep 2007 12:06:44 GMT (162kb)

Title: Quantum-field dynamics of expanding and contracting Bose-Einstein
condensates
Authors: S. Wuester, B.J. Dabrowska-Wuester, S.M. Scott, J.D. Close and C.M.
Savage
Categories: cond-mat.other
\\
We analyze the dynamics of quantum statistics in a harmonically trapped
Bose-Einstein condensate, whose two-body interaction strength is controlled via
a Feshbach resonance. From an initially non-interacting coherent state, the
quantum field undergoes Kerr squeezing, which can be qualitatively described
with a single mode model. To render the effect experimentally accessible, we
propose a homodyne scheme, based on two hyperfine components, which converts
the quadrature squeezing into number squeezing. The scheme is numerically
demonstrated using a two-component Hartree-Fock-Bogoliubov formalism.
\\ ( http://arxiv.org/abs/0709.1362 , 162kb)
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arXiv:0709.1444
Date: Mon, 10 Sep 2007 16:38:31 GMT (64kb)

Title: Fermi-Bose transformation for the time-dependent Lieb-Liniger gas
Authors: H. Buljan, R. Pezer, T. Gasenzer
Categories: cond-mat.other
\\
An approach to calculate the exact time-evolution of a Lieb-Liniger (LL) gas
of locally interacting bosons in one spatial dimension is presented. The
many-body wave function is constructed by transforming a fully antisymmetric
(fermionic) time-dependent wave function which obeys the Schr\" odinger
equation for a free gas. This transformation employs a differential operator
which depends on the strength of the interaction and the number of particles.
The solution thus generalizes Girardeau's Fermi-Bose mapping, valid for
"impenetrable-core" bosons, to any interaction strength. The scheme is used to
exactly calculate the free expansion of a LL gas with localized initial density
distribution.
\\ ( http://arxiv.org/abs/0709.1444 , 64kb)
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arXiv:0709.1335
Date: Mon, 10 Sep 2007 09:40:43 GMT (391kb)

Title: Interference of Spontaneous Emission of Light from Two Atomic Ensembles
Authors: M. Afzelius, M. U. Staudt, H. de. Riedmatten, C. Simon, S. R.
Hastings-Simon, R. Ricken, H. Suche, W. Sohler and N. Gisin
Categories: quant-ph
Comments: submitted to New Journal of Physics
\\
We demonstrate interference of spontaneous emission of light from two distant
solid-state atomic ensembles, when both ensembles are coherently excited by a
common laser source. Owing to a strong collective enhancement of the
spontaneous emission, the atoms behave as ideal two-level quantum systems and
no which-path information is left in the atomic ensembles after emission of a
photon. This allows us to observe a high fringe visibility of 95%. Our
experiment clearly demonstrates the coherent nature of spontaneous emission.
\\ ( http://arxiv.org/abs/0709.1335 , 391kb)
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arXiv:0709.1342
Date: Mon, 10 Sep 2007 10:44:31 GMT (569kb)

Title: Electro-optic control of atom-light interactions using Rydberg
dark-state polaritons
Authors: M. G. Bason, A. K. Mohapatra, K. J. Weatherill and C. S. Adams
Categories: quant-ph
\\
We demonstrate a multiphoton Rydberg dark resonance where a Lambda-system is
coupled to a Rydberg state. This N-type level scheme combines the ability to
slow and store light pulses associated with long lived ground state
superpositions, with the strongly interacting character of Rydberg states. For
the nd_{5/2} Rydberg state in 87Rb (with n=26 or 44) and a beam size of 1 mm we
observe a resonance linewidth of less than 100 kHz in a room temperature atomic
ensemble limited by transit-time broadening. The resonance is switchable with
an electric field of order 1 V/cm. We show that, even when photons with
different wavevectors are involved, the resonance can be Doppler-free.
Applications in electro-optic switching and photonic phase gates are discussed.
\\ ( http://arxiv.org/abs/0709.1342 , 569kb)
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arXiv:0709.1352
Date: Mon, 10 Sep 2007 11:36:23 GMT (561kb)

Title: Quantum Phase Transitions of Light in the Dicke-Bose-Hubbard model
Authors: Soi-Chan Lei and Ray-Kuang Lee
Categories: quant-ph
\\
We extend the idea of quantum phase transitions of light in atom-photon
system with Dicke-Bose-Hubbard model for arbitrary number of two-level atoms.
The formulations of eigenenergies, effective Rabi frequencies, and critical
chemical potentials for two atoms are derived. With a self-consistent method,
we obtain a complete phase diagram for two two-level atoms on resonance, which
indicates the transition from Mott insulator to superfluidity and with a mean
excitations diagram for confirmation. We illustrate the generality of the
method by constructing the dressed-state basis for arbitrary number of
two-level atoms. In addition, we show that the Mott insulator lobes in the
phase diagrams will smash out with the increase of atom numbers. The results of
this work provide a step for studying the effects with combinations of
Dicke-like and Hubbard-like models to simulate strongly correlated electron
systems using photons.
\\ ( http://arxiv.org/abs/0709.1352 , 561kb)
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arXiv:0709.1424
Date: Mon, 10 Sep 2007 15:40:42 GMT (61kb)

Title: Gauss sum factorization with cold atoms
Authors: M. Gilowski, T. Wendrich, T. M\"uller, Ch. Jentsch, W. Ertmer, E. M.
Rasel, and W. P. Schleich
Categories: quant-ph
\\
We report the first implementation of a Gauss sum factorization algorithm by
an internal state Ramsey interferometer using cold atoms. A sequence of
appropriately designed light pulses interacts with an ensemble of cold rubidium
atoms. The final population in the involved atomic levels determines a Gauss
sum. With this technique we factor the number N=263193.
\\ ( http://arxiv.org/abs/0709.1424 , 61kb)
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arXiv:0709.1511
Date: Tue, 11 Sep 2007 00:15:05 GMT (564kb)

Title: Competition between attractive and repulsive interactions in
two-component Bose-Einstein condensates trapped in an optical lattice
Authors: Michal Matuszewski, Boris A. Malomed, Marek Trippenbach
Categories: cond-mat.other
\\
We consider effects of inter-species attraction on two-component gap solitons
(GSs) in the binary BEC with intra-species repulsion, trapped in the
one-dimensional optical lattice (OL). Systematic simulations of the coupled
Gross-Pitaevskii equations (GPEs) corroborate an assumption that, because the
effective mass of GSs is negative, the inter-species attraction may
\emph{split} the two-component soliton. Two critical values, $\kappa_{1}$ and
$\kappa_{2}$, of the OL strength ($\kappa$) are identified. Two-species GSs
with fully overlapping wave functions are stable in strong lattices ($\kappa >\kappa_{1}$). In an intermediate region, $\kappa_{1}>\kappa >\kappa_{2}$, the
soliton splits into a double-humped state with separated components. Finally,
in weak lattices ($\kappa <\kappa_{2}$%), the splitting generates a pair of
freely moving single-species GSs. We present and explain the dependence of
$\kappa_{1}$ and $\kappa_{2}$ on thenumber of atoms (total norm), and on the
relative strength of the competing inter-species attraction and intra-species
repulsion. The splitting of asymmetric solitons, with unequal norms of the two
species, is briefly considered too. It is found and explained that the
splitting threshold grows with the increase of the asymmetry.
\\ ( http://arxiv.org/abs/0709.1511 , 564kb)
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arXiv:0709.1542
Date: Tue, 11 Sep 2007 08:17:21 GMT (121kb)

Title: Coherent particle oscillations between two Bose-Einstein condensates
mediated by a single localized impurity atom
Authors: Uwe R. Fischer, Christian Iniotakis, Anna Posazhennikova
Categories: cond-mat.other
Comments: 4 pages of RevTex4, 4 figures
\\
We study an atomic quantum dot representing a single hyperfine impurity''
atom which is coherently coupled to two well-separated Bose-Einstein
condensates. It is demonstrated that the quantum dot by itself can induce
coherent oscillations of the particle imbalance between the condensates even
when the conventional tunneling between the two condensates can be completely
neglected. In the limit of noninteracting condensates, we provide an
approximate analytical solution to the coupled nonlinear equations of motion
which is in excellent agreement with the full numerical treatment.
\\ ( http://arxiv.org/abs/0709.1542 , 121kb)
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arXiv:0709.1617
Date: Tue, 11 Sep 2007 13:19:05 GMT (12kb)

Title: Frequency and damping of the Scissors Mode of a Fermi gas
Authors: G. M. Bruun and H. Smith
Categories: cond-mat.stat-mech cond-mat.other
\\
We calculate the frequency and damping of the scissors mode in a classical
gas as a function of temperature and coupling strength. Our results show good
agreement with the main features observed in recent measurements of the
scissors mode in an ultracold gas of $^6$Li atoms. The comparison between
theory and experiment involves no fitting parameters and thus allows an
identification of non-classical effects at and near the unitarity limit.
\\ ( http://arxiv.org/abs/0709.1617 , 12kb)
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arXiv:0709.1669
Date: Tue, 11 Sep 2007 16:12:00 GMT (492kb)

Title: Mott transition of fermionic atoms in a three-dimensional optical trap
Authors: R. W. Helmes, T. A. Costi and A. Rosch
Categories: cond-mat.str-el
Comments: 4 pages and 5 figures
\\
We study theoretically the Mott metal-insulator transition for a system of
fermionic atoms confined in a three-dimensional optical lattice and a harmonic
trap. We describe an inhomogeneous system of several thousand sites using an
adaptation of dynamical mean field theory solved efficiently with the numerical
renormalization group method. Above a critical value of the on-site
interaction, a Mott-insulating phase appears in the system. We investigate
signatures of the Mott phase in the density profile and in time-of-flight
experiments.
\\ ( http://arxiv.org/abs/0709.1669 , 492kb)
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arXiv:0709.1690
Date: Tue, 11 Sep 2007 17:52:10 GMT (58kb)

Title: Equilibrium and dynamics of a trapped superfluid Fermi gas with unequal
masses
Authors: G. Orso, L.P. Pitaevskii and S. Stringari
Categories: cond-mat.soft cond-mat.supr-con
\\
Interacting Fermi gases with equal populations but unequal masses are
investigated at zero temperature using local density approximation and the
hydrodynamic theory of superfluids in the presence of harmonic trapping.
We derive the conditions of energetic stability of the superfluid
configuration with respect to phase separation and the frequencies of the
collective oscillations in terms of the mass ratio and the trapping frequencies
of the two components. We discuss the behavior of the gas after the trapping
potential of a single component is switched off and show that, near a Feshbach
resonance, the released component can still remain trapped due to many-body
interaction effects. Explicit predictions are presented for a mixture of $^6$Li
and $^{40}$K with resonant interaction.
\\ ( http://arxiv.org/abs/0709.1690 , 58kb)
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arXiv:0709.1533
Date: Tue, 11 Sep 2007 07:04:13 GMT (331kb)

Title: Bright continuous-variable entanglement from the quantum optical dimer
Authors: M.J. Mallon, M.D. Reid and M.K. Olsen
Categories: quant-ph
Comments: 19 pages, 13 figures, theoretical
\\
We show theoretically that two evanescently coupled $\chi^{(2)}$ second
harmonic generators inside a Fabry-Perot cavity provide a tunable source of
quadrature squeezed light, Einstein-Podolsky-Rosen correlations and quantum
entanglement. Unlike systems using coupled downconverters, second harmonic
generation has no oscillation threshhold, so that the entangled fields become
macroscopically occupied as soon as the pumping fields are turned on. This
system also gives two frequencies at which the entangled fields can have
macroscopic intensity. We show how the entanglement properties can be
controlled by adjusting the pumping, the coupling strengths and the cavity
detunings.
\\ ( http://arxiv.org/abs/0709.1533 , 331kb)
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arXiv:0709.1763
Date: Wed, 12 Sep 2007 06:59:30 GMT (76kb)

Title: Trions, pairing and phase transitions in one-dimensional strongly
attractive three-component ultracold fermions
Authors: X.W. Guan, M.T. Batchelor, C. Lee and H.-Q. Zhou
Categories: cond-mat.stat-mech cond-mat.str-el
\\
We investigate the nature of trions, pairing and quantum phase transitions in
one-dimensional three-component ultracold fermions. Exact results for the
ground state energy, phase diagrams, critical fields and magnetization are
obtained analytically from the Bethe ansatz solution. At zero temperature,
unequally spaced Zeeman splitting triggers exotic phases of trions, bound
pairs, a normal Fermi liquid and four mixtures of these states. In contrast,
for equally spaced Zeeman splitting, a critical field $H_{c1}$ is required to
break the trionic phase. A fully-polarized normal Fermi liquid occurs when the
field is greater than the upper critical value $H_{c2}$. A mixture of trions
and unpaired fermions occurs for $H_{c1}<H<H_{c2}$.
\\ ( http://arxiv.org/abs/0709.1763 , 76kb)
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arXiv:0709.1825
Date: Wed, 12 Sep 2007 12:15:52 GMT (406kb)

Title: Cold Atoms and Molecules in Self-Assembled Dipolar Lattices
Authors: G. Pupillo, A. Griessner, A. Micheli, M. Ortner, D.-W. Wang, and P.
Zoller
Categories: cond-mat.other
\\
We study the realization of lattice models, where cold atoms and molecules
move as extra particles in a dipolar crystal of trapped polar molecules. The
crystal is a self-assembled floating mesoscopic lattice structure with quantum
dynamics given by phonons. We show that within an experimentally accessible
parameter regime extended Hubbard models with tunable long-range
phonon-mediated interactions describe the effective dynamics of dressed
particles.
\\ ( http://arxiv.org/abs/0709.1825 , 406kb)
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arXiv:0709.1899
Date: Wed, 12 Sep 2007 15:32:52 GMT (58kb)

Title: Yang-Yang thermodynamics on an atom chip
Authors: A.H. van Amerongen, J.J.P. van Es, P. Wicke, K.V. Kheruntsyan, N.J.
van Druten
Categories: cond-mat.other
\\
We investigate the behavior of a weakly interacting nearly one-dimensional
(1D) trapped Bose gas at finite temperature. We perform in situ measurements of
spatial density profiles and show that they are very well described by a model
based on exact solutions obtained using the Yang-Yang thermodynamic formalism,
in a regime where other, approximate theoretical approaches fail. We
demonstrate Bose gas focusing as a means to gain experimental access to the
axial momentum distribution of the gas, and find good agreement with the in
situ results.
\\ ( http://arxiv.org/abs/0709.1899 , 58kb)
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arXiv:0709.1938
Date: Wed, 12 Sep 2007 18:18:30 GMT (294kb)

Title: Partial delocalization of two-component condensates in optical lattices
Authors: H. A. Cruz, V. A. Brazhnyi, V. V. Konotop
Categories: cond-mat.other
\\
We study management of localized modes in two-component (spinor)
Bose-Einstein condensates embedded in optical lattices by changing interspecies
interactions. By numerical integration of the coupled Gross-Pitaevskii
equations, we find three different regimes of the delocalizing transition: i)
the partial delocalization when the chemical potential of one of the components
collapses with a gap edge and the respective component transforms into a Bloch
state, while the other component remains localized; ii) the partial
delocalization as consequence of instability of one of the components; and iii)
the situation where the vector soliton reaches limits of the existence domain.
It is shown that there exists a critical value for interspecies scattering
length, below which solutions can be manipulated and above which one of the
components is irreversibly destroyed.
\\ ( http://arxiv.org/abs/0709.1938 , 294kb)
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arXiv:0709.1785
Date: Wed, 12 Sep 2007 10:05:00 GMT (504kb)

Title: Storage and Retrieval of a Squeezed Vacuum
Authors: Kazuhito Honda, Daisuke Akamatsu, Manabu Arikawa, Yoshihiko Yokoi,
Keiichirou Akiba, Satoshi Nagatsuka, Takahito Tanimura, Akira Furusawa, Mikio
Kozuma
Categories: quant-ph
\\
Quantum entanglement plays a central role for implementing quantum
information processing. Deterministic control of quantum entanglement has been
realized using a squeezed vacuum state. However, since photons are hard to
localize, coherent transfer of quantum squeezing between information carrying
photons and spatially localized atoms has long been desired. This coherent
transfer is equivalent to the storage and retrieval of quantum entanglement and
is one of the most important building blocks for implementing the intricate
tasks of quantum information processing. Here, for the first time, we
successfully demonstrate the storage and retrieval of a squeezed vacuum state
with electromagnetically induced transparency using a cold ensemble of Rb atoms
as a memory medium. These results will lead to the deterministic manipulation
of quantum fluctuations of atoms as well as the generation of highly
non-classical atomic states.
\\ ( http://arxiv.org/abs/0709.1785 , 504kb)
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arXiv:0709.1810
Date: Wed, 12 Sep 2007 11:38:49 GMT (319kb)

Title: Shaping the waveform of entangled photons
Authors: Alejandra Valencia, Alessandro Cer\e, Xiaojuan Shi, Gabriel
Molina-Terriza, and Juan P. Torres
Categories: quant-ph
\\
We demonstrate experimentally the tunable control of the joint spectrum, i.e.
waveform and degree of frequency correlations, of paired photons generated in
spontaneous parametric downconversion. This control is mediated by the spatial
shape of the pump beam in a type-I noncollinear configuration. We discuss the
applicability of this technique to other sources of frequency entangled
photons, such as electromagnetically induced Raman transitions.
\\ ( http://arxiv.org/abs/0709.1810 , 319kb)
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arXiv:0709.1703 (*cross-listing*)
Date: Tue, 11 Sep 2007 19:14:08 GMT (17kb)

Title: Existence, uniqueness and approximation of stochastic Schrodinger
equation: the diffusive case
Authors: Clement Pellegrini (ICJ)
Categories: math.PR quant-ph
Proxy: ccsd hal-00171129
\\
Recent developments in quantum physics make heavy use of so-called quantum
trajectories''. Mathematically, this theory gives rise to stochastic
Schr\"odinger equations'', that is, pertubations of Schrodinger-type equations
under the form of stochastic differential equations. But such equations are in
general not of the usual type as considered in the litterature. They pose a
serious problem in terms of: justifying the existence and uniqueness of a
we concentrate on a particular case: the diffusive case, for a two-level
system. We prove existence and uniqueness of the associated stochastic
Schrodinger equation. We physically justify the equations by proving that they
are continuous time limit of a concrete physical procedure for obtainig quantum
trajectory.
\\ ( http://arxiv.org/abs/0709.1703 , 17kb)
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arXiv:0709.1900
Date: Wed, 12 Sep 2007 15:19:28 GMT (41kb)

Title: Quantum Chaos and Regularity in Ultracold Fermi Gases
Authors: M. Puig von Friesen, M. Ogren and S. Aberg
Categories: physics.atom-ph
\\
Quantum fluctuation of the energy is studied for an ultracold gas of
interacting fermions trapped in a three-dimensional potential. Periodic-orbit
theory is explored, and energy fluctuations are studied versus particle number
for generic regular and chaotic systems, as well for a system defined by a
harmonic confinement potential. Temperature effects on the energy fluctuations
are investigated.
\\ ( http://arxiv.org/abs/0709.1900 , 41kb)
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arXiv:0709.1906
Date: Wed, 12 Sep 2007 15:28:40 GMT (71kb)

Title: Factorization of Numbers with the temporal Talbot effect: Optical
implementation by a sequence of shaped ultrashort pulses
Authors: Damien Bigourd (LCAR), B\'eatrice Chatel (LCAR), Wolfgang P. Schleich,
Bertrand Girard (LCAR)
Categories: physics.optics
Proxy: ccsd hal-00171664
\\
We report on the successful operation of an analogue computer designed to
factor numbers. Our device relies solely on the interference of classical light
and brings together the field of ultrashort laser pulses with number theory.
Indeed, the frequency component of the electric field corresponding to a
sequence of appropriately shaped femtosecond pulses is determined by a Gauss
sum which allows us to find the factors of a number.
\\ ( http://arxiv.org/abs/0709.1906 , 71kb)
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arXiv:0709.2004
Date: Thu, 13 Sep 2007 14:56:57 GMT (893kb)

Title: Bright Solitary-Matter-Wave Collisions in a Harmonic Trap: Regimes of
Soliton-like Behaviour
Authors: A. D. Martin, C. S. Adams and S. A. Gardiner
Categories: cond-mat.other
\\
Systems of solitary-waves in the 1D Gross-Pitaevskii equation, which models a
trapped atomic Bose-Einstein condensate, are investigated theoretically. To
analyse the soliton-like nature of these solitary-waves, a particle analogy for
the solitary-waves is formulated. Exact soliton solutions exist in the absence
of an external trapping potential, which behave in a particle-like manner, and
we find the particle analogy we employ to be a good model also when a harmonic
trapping potential is present. In the case of two solitons, the particle model
is integrable, and the dynamics are completely regular. The extension to three
particles supports chaotic regimes. The agreement between the particle model
and the wave dynamics remains good even in chaotic regimes. In the case of a
system of two solitary waves of equal norm, the solitons are shown to retain
their phase difference for repeated collisions. This implies that soliton-like
regimes may be found in 3D geometries where solitary waves can be made to
repeatedly collide out of phase, stabilising the condensate against collapse.
\\ ( http://arxiv.org/abs/0709.2004 , 893kb)
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\\
arXiv:0709.2094
Date: Thu, 13 Sep 2007 15:28:57 GMT (75kb,D)

Title: Quantum spin dynamics of squeezed Luttinger liquids in two-component
atomic gases
Authors: Artur Widera, Stefan Trotzky, Patrick Cheinet, Simon F\"olling,
Fabrice Gerbier, Immanuel Bloch, Vladimir Gritsev, Mikhail D. Lukin and
Eugene Demler
Categories: cond-mat.other
\\
We report on the observation of the phase dynamics of interacting
one-dimensional ultracold bosonic gases with two internal degrees of freedom.
By controlling the non-linear atomic interactions close to a Feshbach resonance
we are able to induce a phase diffusive many-body spin dynamics. We monitor
this dynamical evolution by Ramsey interferometry, supplemented by a novel,
many-body echo technique. We find that the time evolution of the system is well
described by a Luttinger liquid initially prepared in a multimode squeezed
state. Our approach allows us to probe the non-equilibrium evolution of
one-dimensional many-body quantum systems.
\\ ( http://arxiv.org/abs/0709.2094 , 75kb)
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\\
arXiv:0709.2100
Date: Thu, 13 Sep 2007 15:20:09 GMT (92kb,D)

Title: Real Time Evolution in Quantum Many-Body Systems With Unitary
Perturbation Theory
Authors: A. Hackl and S. Kehrein
Categories: cond-mat.str-el
\\
We develop a new analytical method for solving real time evolution problems
of quantum many-body systems. Our approach is a direct generalization of the
well-known canonical perturbation theory for classical systems. Similar to
canonical perturbation theory, secular terms are avoided in a systematic
expansion and one obtains stable long-time behavior. These general ideas are
illustrated by applying them to the spin-boson model and studying its
non-equilibrium spin dynamics.
\\ ( http://arxiv.org/abs/0709.2100 , 92kb)
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\\
arXiv:0709.1986
Date: Thu, 13 Sep 2007 03:50:11 GMT (18kb)

Title: Quantum walk and quantum phase transition in optical lattice
Authors: C. M. Chandrashekar and Raymond Laflamme
Categories: quant-ph
\\
We show that the quantum walk and its properties can be exploited to
redistribute the ultra-cold atoms in optical lattice into desired density
profile and quadratically speed up the the process of quantum phase transition.
We show this by evolving the density profile with every step of quantum walk by
numerical integration, where the correlation during the evolution can be
theoretically studied. We also discuss, how this can be implemented in the
realistic physical situations.
\\ ( http://arxiv.org/abs/0709.1986 , 18kb)
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\\
arXiv:0709.2011
Date: Thu, 13 Sep 2007 15:09:10 GMT (187kb)

Title: Highly non-Gaussian states created via cross-Kerr nonlinearity
Authors: Tomas Tyc and Natalia Korolkova
Categories: quant-ph
\\
We propose a feasible scheme for generation of strongly non-Gaussian states
using the cross-Kerr nonlinearity. The resultant states are highly
non-classical states of electromagnetic field and exhibit negativity of their
Wigner function, sub-Poissonian photon statistics, and amplitude squeezing.
Furthermore, the Wigner function has a distinctly pronounced banana'' or
crescent'' shape specific for the Kerr-type interactions, which so far was
not demonstrated experimentally. We show that creating and detecting such
states should be possible with the present technology using electromagnetically
induced transparency in a four-level atomic system in N-configuration.
\\ ( http://arxiv.org/abs/0709.2011 , 187kb)
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\\
arXiv:0709.2095
Date: Thu, 13 Sep 2007 15:04:28 GMT (719kb)

Title: Probing quantum vacuum geometrical effects with cold atoms
Authors: Diego A. R. Dalvit, Paulo A. Maia Neto, Astrid Lambrecht, Serge
Reynaud
Categories: quant-ph
\\
The lateral Casimir-Polder force between an atom and a corrugated surface
should allow one to study experimentally non trivial geometrical effects in
quantum vacuum. Here, we derive the theoretical expression of this force in a
scattering approach that accounts for the optical properties of the corrugated
surface. We show that large corrections to the proximity force
approximation'' could be measured using present-day technology with a
Bose-Einstein condensate used as a vacuum field sensor.
\\ ( http://arxiv.org/abs/0709.2095 , 719kb)
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\\
arXiv:0709.2132
Date: Thu, 13 Sep 2007 17:13:33 GMT (177kb)

Title: Dynamics of vortices in weakly interacting Bose-Einstein condensates
Authors: Alexander Klein, Dieter Jaksch, Yanzhi Zhang and Weizhu Bao
Categories: quant-ph
Comments: 8 pages, 7 figures, accepted for publication in Phys. Rev. A
\\
We study the dynamics of vortices in ideal and weakly interacting
Bose-Einstein condensates using a Ritz minimization method to solve the
two-dimensional Gross-Pitaevskii equation. For different initial vortex
configurations we calculate the trajectories of the vortices. We find
conditions under which a vortex-antivortex pair annihilates and is created
again. For the case of three vortices we show that at certain times two
additional vortices may be created, which move through the condensate and
annihilate each other again. For a non-interacting condensate this process is
periodic, whereas for small interactions the essential features persist, but
the periodicity is lost. The results are compared to exact numerical solutions
of the Gross-Pitaevskii equation confirming our analytical findings.
\\ ( http://arxiv.org/abs/0709.2132 , 177kb)
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\\
arXiv:0709.2143
Date: Thu, 13 Sep 2007 18:42:21 GMT (127kb)

Title: Optimized Double-well quantum interferometry with Gaussian
squeezed-states
Authors: Y. P. Huang and M. G. Moore
Categories: quant-ph
\\
A Mach-Zehnder interferometer with a Gaussian number-squeezed input state can
exhibit beyond standard-quantum-limit (SQL) phase resolution over a large range
of measured phase-shifts in $(-\pi/2,\pi/2)$. For a single measurement, the
smallest achievable phase uncertainty is $1.63 \tan^{1/3}|\theta|/N^{2/3}$ for
nonzero phase $\theta$. Due to the explicit $\theta$ dependence, the
uncertainty converges quickly to Heisenberg scaling $\sim 1/N$ with only a few
degrade to worse than SQL for nonzero phases, and are not amenable to multiple
in a double-well Bose-Einstein condensate system.
\\ ( http://arxiv.org/abs/0709.2143 , 127kb)
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The replacements:

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\\
arXiv:cond-mat/0703322
replaced with revised version Mon, 10 Sep 2007 12:53:29 GMT (355kb)

Title: Heteronuclear molecules in an optical lattice: Theory and experiment
Authors: Frank Deuretzbacher, Kim Plassmeier, Daniela Pfannkuche, F\'elix
Werner, Christian Ospelkaus, Silke Ospelkaus, Klaus Sengstock, Kai Bongs
Categories: cond-mat.other physics.atom-ph
\\ ( http://arxiv.org/abs/cond-mat/0703322 , 355kb)
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\\
arXiv:0707.2625
replaced with revised version Mon, 10 Sep 2007 09:00:27 GMT (33kb)

Title: Radio Frequency Spectroscopy of Trapped Fermi Gases with Population
Imbalance
Authors: Yan He, Chih-Chun Chien, Qijin Chen, and K. Levin
Categories: cond-mat.str-el cond-mat.supr-con
Comments: 4 page, 3 figures, submitted to PRA Rapid
\\ ( http://arxiv.org/abs/0707.2625 , 33kb)
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\\
arXiv:0706.1840
replaced with revised version Tue, 11 Sep 2007 09:06:09 GMT (301kb)

Title: Vortex pump for dilute Bose-Einstein condensates
Authors: Mikko Mottonen, Ville Pietila, Sami M. M. Virtanen
Categories: cond-mat.mes-hall cond-mat.other
\\ ( http://arxiv.org/abs/0706.1840 , 301kb)
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\\
arXiv:0709.0362
replaced with revised version Tue, 11 Sep 2007 07:12:49 GMT (230kb)

Title: Non-perturbative renormalization-group approach to zero-temperature Bose
systems
Authors: N. Dupuis and K. Sengupta
Categories: cond-mat.other hep-th
\\ ( http://arxiv.org/abs/0709.0362 , 230kb)
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\\
arXiv:0705.1634 (*cross-listing*)
replaced with revised version Wed, 12 Sep 2007 15:17:53 GMT (142kb)

Title: Relativistic BCS-BEC Crossover at Finite Temperature and Its Application
to Color Superconductivity
Authors: Lianyi He and Pengfei Zhuang
Categories: hep-ph astro-ph cond-mat.supr-con nucl-th
Comments: 13 pages, 7 figures. V2: comparision with other theories and new
results on color superconductivity are added. V3: version published in PRD
Journal-ref: Phys. Rev. D 76, 056003 (2007)
DOI: 10.1103/PhysRevD.76.056003
\\ ( http://arxiv.org/abs/0705.1634 , 142kb)
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\\
arXiv:0707.0383
replaced with revised version Wed, 12 Sep 2007 16:52:14 GMT (208kb)

Title: Pair condensation of bosonic atoms induced by optical lattices
Authors: Maria Eckholt, Juan Jose Garcia-Ripoll
Categories: cond-mat.other quant-ph
Report-no: NSF-KITP-07-155
\\ ( http://arxiv.org/abs/0707.0383 , 208kb)
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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 Sun Oct 07 2007 - 00:55:00 EST

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