# Matt's arXiv selection, Monday 3rd April 2005.

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Mon, 3 Apr 2006 11:43:18 +1000 (EST)

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

Lots of preprints this week! Instructions on signing up to this email can be
found here:

If anyone out there is looking for an experimental postdoctoral position in
quantum atom optics in a warm sunny climate, you might like to look at this:

Till next week,
Matt.

--
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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/
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Paper: cond-mat/0603639
Date: Fri, 24 Mar 2006 01:10:45 GMT   (10kb)
Title: Molecular Bose-Einstein condensates, resonance chemistry, and
enhancement of weak interactions
Authors: V.V. Flambaum, J.S.M. Ginges
Subj-class: Other
\\
With the creation of atomic and molecular Bose-Einstein condensates (BECs), a
new type of chemistry - "resonance" chemistry - emerges: chemical reactions can
occur when the energy of colliding atoms/molecules matches a bound state of the
combined molecule (Feshbach resonance). This chemistry is rather similar to
reactions that take place in nuclei at low energies. In this paper we suggest
some problems for future experimental and theoretical work related to the
resonance chemistry of molecular BECs. Molecular BECs are particularly
interesting because in this system collisions and chemical reactions are
extremely sensitive to weak fields. This sensitivity arises due to the high
density of narrow compound resonances and the macroscopic number of molecules
with kinetic energy E=0 (more accurately, in the ground state of a mean-field
potential). The high sensitivity to the magnetic field may be used to measure
the distribution of energy intervals, widths, and magnetic moments of compound
resonances and study the onset of quantum chaos. A difference in the production
rate of right-handed and left-handed chiral molecules may be produced by
external electric and magnetic fields and the finite width of the resonance.
The same effect may be produced by the parity-violating energy difference in
chiral molecules.
\\ ( http://arXiv.org/abs/cond-mat/0603639 ,  10kb)
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Paper: cond-mat/0603643
Date: Fri, 24 Mar 2006 06:46:59 GMT   (61kb)
Title: The 1D interacting anyon gas: low-energy properties and Haldane
exclusion statistics
Authors: M.T. Batchelor, X.-W. Guan and N. Oelkers
Subj-class: Statistical Mechanics
\\
The low energy properties of the one-dimensional anyon gas with
$\delta$-function interaction are discussed in the context of its Bethe ansatz
solution. It is found that the anyonic statistical parameter and the dynamical
coupling constant induce Haldane exclusion statistics interpolating between
bosons and fermions. Moreover, the anyonic parameter may trigger statistics
beyond Fermi statistics for which the Haldane exclusion parameter $\alpha$ is
greater than one. The model is discussed in detail in the Tonks-Girardeau and
the weak coupling limits. The results support the universal role of $\alpha$ in
the dispersion relations.
\\ ( http://arXiv.org/abs/cond-mat/0603643 ,  61kb)
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Paper: cond-mat/0603654
Date: Fri, 24 Mar 2006 14:10:55 GMT   (449kb)
Title: Dynamical density-density correlations in the one-dimensional Bose gas
Authors: J.-S. Caux and P. Calabrese
Subj-class: Statistical Mechanics
\\
The zero-temperature dynamical structure factor of the one-dimensional Bose
gas with delta-function interaction (Lieb-Liniger model) is computed using a
hybrid theoretical/numerical method based on the exact Bethe Ansatz solution,
which allows to interpolate continuously between the weakly-coupled
Thomas-Fermi and strongly-coupled Tonks-Girardeau regimes. The results should
be experimentally accessible with Bragg spectroscopy.
\\ ( http://arXiv.org/abs/cond-mat/0603654 ,  449kb)
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Paper: cond-mat/0603655
Date: Fri, 24 Mar 2006 14:18:28 GMT   (565kb)
Title: Onset of a Bose-Glass of ultracold atoms in a disordered crystal of
light
Authors: L. Fallani, J. E. Lye, V. Guarrera, C. Fort, M. Inguscio
Subj-class: Other
\\
Disorder is ubiquitous in nature, manifesting itself in many key physical and
biological processes. It plays a fundamental role in the physics of conduction
in metals and in the superfluid-insulator transition occurring in many
condensed-matter systems. Ultracold atoms in optical potentials can be used as
"quantum simulators" to model such disordered systems, taking advantage of the
possibility to accurately control the kind and amount of disorder. Starting
from a Mott Insulator state, we use a bichromatic optical lattice to add
controlled disorder to an ideal optical crystal where bosonic atoms are pinned
by repulsive interactions. Increasing disorder, we observe the onset of a
gapless insulating Bose-Glass phase induced by the cooperation of interactions
and disorder. This observation paves the way to the investigation of new
strongly correlated disordered phases of broad interest even beyond the realm
of physics.
\\ ( http://arXiv.org/abs/cond-mat/0603655 ,  565kb)
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Paper: cond-mat/0603665
Date: Fri, 24 Mar 2006 17:16:38 GMT   (1870kb)
Title: Pseudofermion scattering theory
Authors: J. M. P. Carmelo, D. Bozi, and P. D. Sacramento
Subj-class: Strongly Correlated Electrons
\\
In this paper we study the scattering theory associated with the
pseudofermion dynamical theory for the Hubbard chain. In terms of
pseudofermions the spectral properties are controlled by zero-momentum forward
scattering only. The pseudofermion $S$ matrix is expressed as a commutative
product of $S$ matrices, each corresponding to an elementary two-pseudofermion
scattering event. This commutative factorization is stronger than the usual
factorization associated with Yang-Baxter Equation for the original spin 1/2
electron bare $S$ matrix. Our results reveal the scattering mechanisms which
control the exotic finite-energy spectral properties of the low-dimensional
complex materials and correlated systems of cold fermionic atoms on an optical
lattice. Importantly, the exotic scatterers and scattering centers predicted by
the theory were observed by angle-resolved photoelectron spectroscopy in
low-dimensional organic metals.
\\ ( http://arXiv.org/abs/cond-mat/0603665 ,  1870kb)
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Paper (*cross-listing*): gr-qc/0603093
Date: Thu, 23 Mar 2006 14:36:20 GMT   (469kb)
Title: Black-Hole and White-Hole Horizons in Superfluids
Authors: G.E. Volovik
Comments: 14 pages, 5 Figures, draft for proceedings of the workshop "Universal
features in turbulence: from quantum to cosmological scales", December 2005,
Warwick
Subj-class: General Relativity and Quantum Cosmology; Fluid Dynamics; Soft
Condensed Matter
\\
Ripplons -- gravity-capillary waves on the free surface of a liquid or at the
interfaces between two superfluids -- are the most favourable excitations for
simulation of the general-relativistic effects related to horizons and
ergoregions. The white-hole horizon for the relativistic'' ripplons at the
surface of the shallow liquid is easily simulated using the kitchen-bath
hydraulic jump. The same white-hole horizon is observed in quantum liquid --
superfluid 4He. The ergoregion for the non-relativistic'' ripplons is
generated in the experiments with two sliding 3He superfluids. The common
property experienced by all these ripplons is the Miles instability inside the
ergoregion or horizon. Because of the universality of the Miles instability,
one may expect that it could take place inside the horizon of the astrophysical
black holes, if there is a preferred reference frame which comes from the
trans-Planckian physics. If this is the case, the black hole would evapotate
much faster than due to the Hawking radiation. Hawking radiation from the
artificial black hole in terms of the quantum tunneling of phonons and ripplons
is also discussed.
\\ ( http://arXiv.org/abs/gr-qc/0603093 ,  469kb)
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Paper (*cross-listing*): nlin.PS/0603050
Date: Thu, 23 Mar 2006 12:08:46 GMT   (267kb)
Title: Discrete Solitons in the Salerno Model with competing nonlinearities
Authors: J. Gomez-Gardenes, B.A. Malomed, L.M. Floria, and A.R. Bishop
Subj-class: Pattern Formation and Solitons; Soft Condensed Matter
Journal-ref: Physical Review E 73 036608 (2006)
DOI: 10.1103/PhysRevE.73.036608
\\
We consider a lattice equation (Salerno model) combining onsite self-focusing
and intersite self-defocusing cubic terms, which may describe a Bose-Einstein
condensate of dipolar atoms trapped in a strong periodic potential. In the
continuum approximation, the model gives rise to solitons in a finite band of
frequencies, with sechlike solitons near one edge, and an exact peakon solution
at the other. A similar family of solitons is found in the discrete system,
including a peakon; beyond the peakon, the family continues in the form of
cuspons. Stability of the lattice solitons is explored through computation of
eigenvalues for small perturbations, and by direct simulations. A small part of
the family is unstable (in that case, the discrete solitons transform into
robust pulsonic excitations); both peakons and cuspons are stable. The
Vakhitov-Kolokolov criterion precisely explains the stability of regular
solitons and peakons, but does not apply to cuspons. In-phase and out-of-phase
bound states of solitons are also constructed. They exchange their stability at
a point where the bound solitons are peakons. Mobile solitons, composed of a
moving core and background, exist up to a critical value of the strength of the
self-defocusing intersite nonlinearity. Colliding solitons always merge into a
single pulse.
\\ ( http://arXiv.org/abs/nlin/0603050 ,  267kb)
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Paper: cond-mat/0512103
replaced with revised version Fri, 24 Mar 2006 14:40:34 GMT   (98kb)
Title: Superglass Phase of Helium-four
Authors: M. Boninsegni, N. Prokof'ev and B. Svistunov
Subj-class: Statistical Mechanics
Journal-ref: Phys. Rev. Lett. 96, 105301 (2006)
\\ ( http://arXiv.org/abs/cond-mat/0512103 ,  98kb)
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Paper: cond-mat/0601006
replaced with revised version Thu, 23 Mar 2006 23:16:06 GMT   (67kb)
Title: Trapped Fermions across a Feshbach resonance with population imbalance
Authors: W. Yi and L.-M. Duan
Comments: 4 pages, 3 figures, replaced with the published version
Subj-class: Other
Journal-ref: Phys. Rev. A 73, 031604(R) (2006)
DOI: 10.1103/PhysRevA.73.031604
\\ ( http://arXiv.org/abs/cond-mat/0601006 ,  67kb)
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Paper: cond-mat/0602283
replaced with revised version Fri, 24 Mar 2006 17:14:29 GMT   (118kb)
Title: Time of flight observables and the formation of Mott domains of fermions
and bosons on optical lattices
Authors: M. Rigol, R. T. Scalettar, P. Sengupta, and G. G. Batrouni
Comments: 5 pages, 6 figures, published version
Subj-class: Strongly Correlated Electrons; Superconductivity
Journal-ref: Phys. Rev. B 73, 121103(R) (2006)
DOI: 10.1103/PhysRevB.73.121103
\\ ( http://arXiv.org/abs/cond-mat/0602283 ,  118kb)
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Paper: cond-mat/0603273
replaced with revised version Fri, 24 Mar 2006 11:12:21 GMT   (55kb)
Title: Ultracold atomic F=2 spinor gas in an optical lattice
Authors: L. Zawitkowski, K. Eckert, A. Sanpera, M.Lewenstein
Subj-class: Other
\\ ( http://arXiv.org/abs/cond-mat/0603273 ,  55kb)
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Paper: cond-mat/0603607
replaced with revised version Fri, 24 Mar 2006 05:35:17 GMT   (11kb)
Title: Enhancement of variation of fundamental constants in ultracold atom and
molecule systems near Feshbach resonances
Authors: Cheng Chin, V.V. Flambaum
Subj-class: Other; Disordered Systems and Neural Networks; Atomic Physics
\\ ( http://arXiv.org/abs/cond-mat/0603607 ,  11kb)
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Paper: cond-mat/0603675
Date: Fri, 24 Mar 2006 21:26:29 GMT   (465kb)
Title: Resonator-Aided Single-Atom Detection on a Microfabricated Chip
Authors: Igor Teper, Yu-Ju Lin, Vladan Vuletic
Comments: 4.1 pages, 5 figures, and submitted to Physical Review Letters
Subj-class: Other
\\
We use an optical cavity to detect single atoms magnetically trapped on an
atom chip. We implement the detection using both fluorescence into the cavity
and reduction in cavity transmission due to the presence of atoms. In
fluorescence, we register 2.0(2) photon counts per atom, which allows us to
detect single atoms with 75% efficiency in 250 microseconds. In absorption, we
measure transmission attenuation of 3.3(3)% per atom, which allows us to count
small numbers of atoms with a resolution of about 1 atom.
\\ ( http://arXiv.org/abs/cond-mat/0603675 ,  465kb)
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Paper: cond-mat/0603684
Date: Sat, 25 Mar 2006 09:23:15 GMT   (103kb)
Title: Gauge field in ultra-cold bipartite atoms
Authors: H. Wang, W. Wang, and X. X. Yi
Subj-class: Other
\\
The effects of entanglement and spin-spin collision on the gauge field in
ultracold atoms are presented in this paper. Two gauge fields are calculated
and discussed. One of the fields comes from space dependent spin-spin
collisions in ultra-cold atoms, while another results from the usual
Born-Oppenheimer method, which separates the center-of-mass motion from the
relative motion in the two-body problem. Adiabatic conditions that lead to the
key results of this paper are also presented and discussed. Entanglement shared
between the two atoms is shown to affect the atomic motion. In the presence of
entanglement, the additional scalar potential disappears, this is different
from the case of atoms in separable states.
\\ ( http://arXiv.org/abs/cond-mat/0603684 ,  103kb)
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Paper: cond-mat/0603686
Date: Mon, 27 Mar 2006 16:23:11 GMT   (29kb)
Title: Nonadiabatic production of spinor condensates with a QUIC trap
Authors: P. Zhang, Z. Xu and L. You
Subj-class: Statistical Mechanics
Journal-ref: Phys. Rev. A 73, 013623 (2006)
\\
Motivated by the recent experimental observation of multi-component spinor
condensates via a time-dependent quadrupole-Ioffe-configuration trap (QUIC
trap), we provide a general framework for the investigation of nonadiabatic
Landau-Zener dynamics of a hyperfine spin, e.g., from an atomic magnetic dipole
moment coupled to a weak time-dependent magnetic (B-) field. The spin flipped
population distribution, or the so-called Majorona formula is expressed in
terms of system parameters and experimental observables; thus, provides much
needed insight into the underlying mechanism for the production of spinor
condensates due to nonadiabatic level crossings.
\\ ( http://arXiv.org/abs/cond-mat/0603686 ,  29kb)
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Paper: cond-mat/0603699
Date: Mon, 27 Mar 2006 00:07:31 GMT   (739kb)
Title: Vortex creation during magnetic trap manipulations of spinor
Bose-Einstein condensates
Authors: A.P. Itin, T. Morishita, M. Satoh, O.I. Tolstikhin, and S. Watanabe
Comments: 16 pages, 8 figures (of reduced quality; original figures are
available upon request: alx_it_at_yahoo.com)
Subj-class: Other
\\
We investigate several mechanisms of vortex creation during splitting of a
spinor BEC in a magnetic trap controlled by a pair of current carrying wires
and bias magnetic fields. Our study is motivated by a recent MIT experiment on
splitting BECs with a similar trap, where unexpected fork-like structure
appeared in the interference fringes corresponding to interference of two
condensates, one with and the other without a singly quantized vortex. It is
well known that in a spin-1 BEC in a quadrupole trap a doubly quantized vortex
is produced topologically by reversal of bias magnetic field $B_z$. We find
that in the magnetic trap considered it is also possible to produce a 4- and
1-quantized vortex in a spin-1 BEC. The latter is possible, for example, during
the magnetic field switching-off process. We therefore provide a possible
explanation for the unexpected interference patterns in the experiment. We also
give an example of the creation of singly quantized vortices due to fast
splitting, which is a possible alternative mechanism of the interference
pattern.
\\ ( http://arXiv.org/abs/cond-mat/0603699 ,  739kb)
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Paper: cond-mat/0603709
Date: Mon, 27 Mar 2006 10:36:51 GMT   (138kb)
Title: Quantum squeezing by a parametric resonance in a SQUID
Authors: T. Ojanen, J. Salo
Subj-class: Mesoscopic Systems and Quantum Hall Effect; Superconductivity
\\
We study rotating squeezed quantum states created by a parametric resonance
in an open harmonic system. As a specific realization of the phenomenon we
study a mesoscopic SQUID loop where the state preparation procedure is simple
in principle and feasible with currently available experimental methods. By
solving dynamics and calculating spectral properties we show that quantum
fluctuations of SQUID observables can be reduced below their groundstate value.
The measurement is introduced by coupling the SQUID to a transmission line
carrying the radiation to a secondary measurement device. Besides the
theoretical interest, our studies are motivated by an opportunity for a
practical quantum noise engineering.
\\ ( http://arXiv.org/abs/cond-mat/0603709 ,  138kb)
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Paper: cond-mat/0603710
Date: Mon, 27 Mar 2006 10:51:03 GMT   (73kb)
Title: Regulating entanglement production in multitrap Bose-Einstein
condensates
Authors: V.I. Yukalov and E.P. Yukalova
Subj-class: Mesoscopic Systems and Quantum Hall Effect; Statistical Mechanics
Journal-ref: Phys. Rev. A 73 (2006) 022335-10
\\
A system of traps is considered, each containing a large number of
Bose-condensed atoms. This ensemble of traps is subject to the action of an
external modulating field generating nonequilibrium nonground-state
condensates. When the frequency of the modulating field is in resonance with
the transition frequency between two different topological coherent modes, each
trap becomes an analog of a finite-level resonant atom. Similarly to the case
of atoms in an electromagnetic resonant field, one can create entanglement
between atomic traps subject to a common resonant modulating field generating
higher coherent modes in each of the traps. A method is suggested for
regulating entanglement production in such a system of multitrap and multimode
Bose-Einstein condensates coupled through a common resonant modulating field.
Several regimes of evolutional entanglement production, regulated by
manipulating the external field, are illustrated by numerical calculations.
\\ ( http://arXiv.org/abs/cond-mat/0603710 ,  73kb)
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Paper: cond-mat/0603712
Date: Mon, 27 Mar 2006 12:56:43 GMT   (23kb)
Title: Effect of superradiance on transport of diffusing photons in cold atomic
gases
Authors: A. Gero and E. Akkermans
Comments: 4 pages and 1 figure
Subj-class: Mesoscopic Systems and Quantum Hall Effect
Journal-ref: Physical Review Letters 96, 093601 (2006)
\\
We show that in atomic gases cooperative effects like superradiance and
subradiance lead to a potential between two atoms that decays like $1/r$. In
the case of superradiance, this potential is attractive for close enough atoms
and can be interpreted as a coherent mesoscopic effect. The contribution of
superradiant pairs to multiple scattering properties of a dilute gas, such as
photon elastic mean free path and group velocity, is significantly different
from that of independent atoms. We discuss the conditions under which these
effects may be observed and compare our results to recent experiments on photon
transport in cold atomic gases.
\\ ( http://arXiv.org/abs/cond-mat/0603712 ,  23kb)
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Paper: cond-mat/0603721
Date: Mon, 27 Mar 2006 19:08:47 GMT   (53kb)
Title: Spectroscopy of ultracold atoms by periodic lattice modulations
Authors: C. Kollath, A. Iucci, T. Giamarchi, W. Hofstetter, U. Schollwoeck
Subj-class: Other
\\
We present a non-perturbative analysis of a new experimental technique for
probing ultracold bosons in an optical lattice by periodic lattice depth
modulations. This is done using the time-dependent density-matrix
renormalization group method. We find that sharp energy absorption peaks are
not unique to the Mott insulating phase at commensurate filling, but also exist
for superfluids at incommensurate filling. For strong interactions the peak
structure provides an experimental measure of the interaction strength.
Moreover, the peak height of the second peak can be employed as a measure of
the incommensurability of the system.
\\ ( http://arXiv.org/abs/cond-mat/0603721 ,  53kb)
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Paper: cond-mat/0512010
replaced with revised version Mon, 27 Mar 2006 09:30:33 GMT   (422kb)
Title: Sound velocity and dimensional crossover in a superfluid Fermi gas in an
optical lattice
Authors: T. Koponen, J.-P. Martikainen, J. Kinnunen, and P. Torma
Comments: 16 pages, 9 figures, replaced with the published version
Subj-class: Superconductivity
Journal-ref: Phys. Rev. A 73, 033620 (2006)
\\ ( http://arXiv.org/abs/cond-mat/0512010 ,  422kb)
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Paper: cond-mat/0512518
replaced with revised version Fri, 24 Mar 2006 22:54:17 GMT   (550kb)
Title: Rapid sympathetic cooling to Fermi degeneracy on a chip
Authors: S. Aubin, S. Myrskog, M. H. T. Extavour, L. J. LeBlanc, D. McKay, A.
Stummer, J. H. Thywissen
Comments: 5 pages, 4 figures (v3: new collision data, improved atom number
calibration, revised text, improved figures.)
Subj-class: Statistical Mechanics
\\ ( http://arXiv.org/abs/cond-mat/0512518 ,  550kb)
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Paper: cond-mat/0603513
replaced with revised version Sun, 26 Mar 2006 12:42:01 GMT   (70kb)
Title: Ultra Cold Atoms in Incommensurate 1D Optical Lattices - an Interacting
Aubry-Andre Model
Authors: Nir Bar-Gill, Rami Pugatch, Eitan Rowen, Nadav Katz, and Nir Davidson
Subj-class: Disordered Systems and Neural Networks
\\ ( http://arXiv.org/abs/cond-mat/0603513 ,  70kb)
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Paper: cond-mat/0603571
replaced with revised version Sun, 26 Mar 2006 06:55:04 GMT   (85kb)
Title: Identifying the Bose glass phase
Authors: R. Pugatch, N. Bar-gill, N. Katz, E. Rowen, N. Davidson
Comments: 4 pages, 3 figures (corrected bibliography)
Subj-class: Soft Condensed Matter; Other
\\ ( http://arXiv.org/abs/cond-mat/0603571 ,  85kb)
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Paper: quant-ph/0603229
Date: Sat, 25 Mar 2006 18:44:55 GMT   (23kb)
Title: Spin Decoherence in Superconducting Atom Chips
Authors: Per Kristian Rekdal, Ulrich Hohenester, Bo-Sture K. Skagerstam, Asier
Eiguren
\\
Using a consistent quantum-mechanical treatment for the electromagnetic
radiation, we theoretically investigate the magnetic spin-flip scatterings of a
neutral two-level atom trapped in the vicinity of a superconducting body. We
derive a simple scaling law for the corresponding spin-flip lifetime for such
an atom trapped near a superconducting thick slab. For temperatures below the
superconducting transition temperature T_c, the lifetime is found to be
enhanced by several orders of magnitude in comparison to the case of a normal
conducting slab. At zero temperature the spin-flip lifetime is given by the
unbounded free-space value.
\\ ( http://arXiv.org/abs/quant-ph/0603229 ,  23kb)
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Paper: quant-ph/0603245
Date: Mon, 27 Mar 2006 18:19:40 GMT   (22kb)
Title: On the statistics of quantum expectations for systems in thermal
equilibrium
Authors: Giovanni Jona-Lasinio, Carlo Presilla
Comments: 6 pages, 2 figures, contribution to Quantum Jumps Conference
\\
The recent remarkable developments in quantum optics, mesoscopic and cold
atom physics have given reality to wave functions. It is then interesting to
explore the consequences of assuming ensembles over the wave functions simply
related to the canonical density matrix. In this note we analyze a previously
introduced distribution over wave functions which naturally arises considering
the Schroedinger equation as an infinite dimensional dynamical system. In
particular, we discuss the low temperature fluctuations of the quantum
expectations of coordinates and momenta for a particle in a double well
potential. Our results may be of interest in the study of chiral molecules.
\\ ( http://arXiv.org/abs/quant-ph/0603245 ,  22kb)
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Paper: physics/0602108
replaced with revised version Mon, 27 Mar 2006 14:40:46 GMT   (516kb)
Title: All-optical generation and photoassociative probing of sodium
Bose-Einstein condensates
Authors: R. Dumke, M. Johanning, E. Gomez, J. D. Weinstein, K. M. Jones and P.
D. Lett
Subj-class: Atomic Physics
\\ ( http://arXiv.org/abs/physics/0602108 ,  516kb)
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Paper: cond-mat/0603732
Date: Tue, 28 Mar 2006 01:26:49 GMT   (37kb)
Title: A basis-set based Fortran program to solve the Gross-Pitaevskii Equation
for dilute Bose gases in harmonic and anharmonic traps
Authors: Rakesh P. Tiwari and Alok Shukla
Comments: 3 figures (included), to appear in Computer Physics Communications
Subj-class: Other; Mesoscopic Systems and Quantum Hall Effect
\\
Inhomogeneous boson systems, such as the dilute gases of integral spin atoms
in low-temperature magnetic traps, are believed to be well described by the
Gross-Pitaevskii equation (GPE). GPE is a nonlinear Schroedinger equation which
describes the order parameter of such systems at the mean field level. In the
present work, we describe a Fortran 90 computer program developed by us, which
solves the GPE using a basis set expansion technique. In this technique, the
condensate wave function (order parameter) is expanded in terms of the
solutions of the simple-harmonic oscillator (SHO) characterizing the atomic
trap. Additionally, the same approach is also used to solve the problems in
which the trap is weakly anharmonic, and the anharmonic potential can be
expressed as a polynomial in the position operators x, y, and z. The resulting
eigenvalue problem is solved iteratively using either the self-consistent-field
(SCF) approach, or the imaginary time steepest-descent (SD) approach. Our
results for harmonic traps are also compared with those published by other
authors using different numerical approaches, and excellent agreement is
obtained. GPE is also solved for a few anharmonic potentials, and the influence
of anharmonicity on the condensate is discussed. Additionally, the notion of
Shannon entropy for the condensate wave function is defined and studied as a
function of the number of particles in the trap. It is demonstrated numerically
that the entropy increases with the particle number in a monotonic way.
\\ ( http://arXiv.org/abs/cond-mat/0603732 ,  37kb)
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Paper: cond-mat/0603744
Date: Tue, 28 Mar 2006 08:33:22 GMT   (7kb)
Title: On the computation of the entropy in the microcanonical ensemble for
mean-field-like systems
Authors: Alessandro Campa
Subj-class: Statistical Mechanics
\\
Two recently proposed expressions for the computation of the entropy in the
microcanonical ensemble are compared, and their equivalence is proved. These
expressions are valid for a certain class of statistical mechanics systems,
that can be called mean-field-like systems. Among these, this work considers
only the systems with the most usual hamiltonian structure, given by a kinetic
energy term plus interaction terms depending only on the configurational
coordinates.
\\ ( http://arXiv.org/abs/cond-mat/0603744 ,  7kb)
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Paper: cond-mat/0603747
Date: Tue, 28 Mar 2006 09:23:03 GMT   (14kb)
Title: Pairing of a harmonically trapped fermionic Tonks-Girardeau gas
Authors: A. Minguzzi, M.D. Girardeau
Comments: 4 pages, 3 figures, revtex4
Subj-class: Superconductivity
\\
The fermionic Tonks-Girardeau (FTG) gas is a one-dimensional spin-polarized
Fermi gas with infinitely strong attractive zero-range odd-wave interactions,
arising from a confinement-induced resonance reachable via a three-dimensional
p-wave Feshbach resonance. We investigate the off-diagonal long-range order
(ODLRO) of the FTG gas subjected to a longitudinal harmonic confinement by
analyzing the two-particle reduced density matrix for which we derive a
closed-form expression. Using a variational approach and numerical
diagonalization we find that the largest eigenvalue of the two-body density
matrix is of order N/2, where N is the total particle number, and hence a
partial ODLRO is present for a FTG gas in the trap.
\\ ( http://arXiv.org/abs/cond-mat/0603747 ,  14kb)
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Paper: cond-mat/0603754
Date: Tue, 28 Mar 2006 12:43:54 GMT   (17kb)
Title: Bose-Einstein Condensation with Entangled Order Parameter
Authors: Yu Shi, Qian Niu
Comments: 5 pages, 4 figures. Accepted by Phys. Rev. Lett
Subj-class: Other
\\
We propose a practically accessible non-mean-field ground state of
Bose-Einstein condensation (BEC), which occurs in an interspecies two-particle
entangled state, and is thus described by an entangled order parameter. A
suitably defined entanglement entropy is used as the characterization of the
non-mean-field nature, and is found to persist in a wide parameter regime. The
interspecies entanglement leads to novel interference terms in the dynamical
equations governing the single particle orbital wavefunctions. Experimental
feasibility and several methods of probe are discussed. We urge the study of
multi-channel scattering between different species of atoms.
\\ ( http://arXiv.org/abs/cond-mat/0603754 ,  17kb)
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Paper: cond-mat/0603772
Date: Tue, 28 Mar 2006 20:02:55 GMT   (186kb)
Title: A condensate interferometer with long coherence time and large arm
separation
Authors: O. Garcia, B. Deissler, K. J. Hughes, J. M. Reeves and C.A. Sackett
Subj-class: Other
\\
A condensate Michelson interferometer is demonstrated with coherence times of
up to 44 ms and arm separations up to 180 micrometers. This coherence time is
four times longer than that of previous condensate interference experiments,
and the arm separation is more than an order of magnitude larger than that
observed for any previous atom interferometer. The device uses atoms weakly
confined in a novel magnetic guide and the atomic motion is controlled using
Bragg interactions with an off-resonant standing wave laser beam.
\\ ( http://arXiv.org/abs/cond-mat/0603772 ,  186kb)
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Paper: quant-ph/0603255
Date: Tue, 28 Mar 2006 09:53:14 GMT   (9kb)
Title: Generation of Entanglement from Nonclassical Photon Statistics
Authors: Solomon Ivan, N. Mukunda, and R. Simon
\\
The ability of the beam splitter to transform nonclassicality beyond
squeezing into entanglement is demonstrated. Taking product state of the form
$\rho_{{\rm in} =\rho_a\otimes |0>_b {_b}< 0|$ as input, we show that the
output of the beam splitter, $\rho_{{\rm out}}$, is entangled whenever the
photon number distribution (PND) statistics $\{p(n_a) \}$ associated with the
possibly mixed state $\rho_a$ of the a_mode is antibunched, or possesses any
other kind of nonclassicality.
\\ ( http://arXiv.org/abs/quant-ph/0603255 ,  9kb)
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Paper: quant-ph/0603256
Date: Tue, 28 Mar 2006 18:12:11 GMT   (693kb)
Title: Quantum Open System Theory: Bipartite Aspects
Authors: Ting Yu and J. H. Eberly
\\
We demonstrate in straightforward calculations that even under ideally weak
noise the relaxation of bipartite open quantum systems contains elements not
previously encountered in quantum noise physics and not predicted by the
standard theory of quantum open systems.
\\ ( http://arXiv.org/abs/quant-ph/0603256 ,  693kb)
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Paper: cond-mat/0603783
Date: Wed, 29 Mar 2006 09:25:06 GMT   (362kb)
Title: Nature of intrinsic relation between Bloch-band tunneling and
modulational instability
Authors: V.A. Brazhnyi, V.V. Konotop, and V. Kuzmiak
Comments: 5 pages, 3 figures, To appear in Phys.Rev.Lett
Subj-class: Soft Condensed Matter
\\
On examples of Bose-Einstein condensates embedded in two-dimensional optical
lattices we show that in nonlinear periodic systems modulational instability
and inter-band tunneling are intrinsically related phenomena. By direct
numerical simulations we found that tunneling results in attenuation or
enhancement of instability. On the other hand, instability results in
asymmetric nonlinear tunneling. The effect strongly depends on the band gap
structure and it is especially significant in the case of the resonant
tunneling. The symmetry of the coherent structures emerging from the
instability reflects the symmetry of both the stable and the unstable states
between which the tunneling occurs. Our results provide an evidence of profound
effect of the band structure on superfluid-insulator transition.
\\ ( http://arXiv.org/abs/cond-mat/0603783 ,  362kb)
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Paper: cond-mat/0603792
Date: Wed, 29 Mar 2006 15:03:44 GMT   (546kb)
Title: Bose-Einstein condensates in fast rotation
Authors: Sabine Stock (LKB - Lhomond), Baptiste Battelier (LKB - Lhomond),
Vincent Bretin (LKB - Lhomond), Zoran Hadzibabic (LKB - Lhomond), Jean
Dalibard (LKB - Lhomond)
Comments: Laser Physics Letters 2, 275 (2005)
Proxy: ccsd ccsd-00021948
Subj-class: Mesoscopic Systems and Quantum Hall Effect
\\
In this short review we present our recent results concerning the rotation of
atomic Bose-Einstein condensates confined in quadratic or quartic potentials,
and give an overview of the field. We first describe the procedure used to set
an atomic gas in rotation and briefly discuss the physics of condensates
containing a single vortex line. We then address the regime of fast rotation in
harmonic traps, where the rotation frequency is close to the trapping
frequency. In this limit the Landau Level formalism is well suited to describe
the system. The problem of the condensation temperature of a fast rotating gas
is discussed, as well as the equilibrium shape of the cloud and the structure
of the vortex lattice. Finally we review results obtained with a quadratic +
quartic potential, which allows to study a regime where the rotation frequency
is equal to or larger than the harmonic trapping frequency.
\\ ( http://arXiv.org/abs/cond-mat/0603792 ,  546kb)
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Paper: cond-mat/0603793
Date: Wed, 29 Mar 2006 15:03:49 GMT   (766kb)
Title: Vortex stability in nearly two-dimensional Bose-Einstein condensates
with attraction
Authors: Dumitru Mihalache, Dumitru Mazilu, Boris A. Malomed, Falk Lederer
Comments: 21 pages, 8 figures, to appear in Physical Review A
Subj-class: Other
\\
We perform accurate investigation of stability of localized vortices in an
effectively two-dimensional ("pancake-shaped") trapped BEC with negative
scattering length. The analysis combines computation of the stability
eigenvalues and direct simulations. The states with vorticity S=1 are stable in
a third of their existence region, $0<N<(1/3)N_{\max}^{(S=1)}$, where $N$ is
the number of atoms, and $N_{\max}^{(S=1)}$ is the corresponding collapse
threshold. Stable vortices easily self-trap from arbitrary initial
configurations with embedded vorticity. In an adjacent interval, $(1/3)N_{\max }^{(S=1)}<N<$ $\allowbreak 0.43N_{\max}^{(S=1)}$, the unstable vortex
periodically splits in two fragments and recombines. At $N>$ $\allowbreak 0.43N_{\max}^{(S=1)}$, the fragments do not recombine, as each one collapses by
itself. The results are compared with those in the full 3D Gross-Pitaevskii
equation. In a moderately anisotropic 3D configuration, with the aspect ratio
$\sqrt{10}$, the stability interval of the S=1 vortices occupies $\approx 40%$
of their existence region, hence the 2D limit provides for a reasonable
approximation in this case. For the isotropic 3D configuration, the stability
interval expands to 65% of the existence domain. Overall, the vorticity
heightens the actual collapse threshold by a factor of up to 2. All vortices
with $S\geq 2$ are unstable.
\\ ( http://arXiv.org/abs/cond-mat/0603793 ,  766kb)
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Paper: cond-mat/0408491
replaced with revised version Tue, 28 Mar 2006 21:23:29 GMT   (59kb)
Title: Vortices in attractive Bose-Einstein condensates in two dimensions
Authors: L. D. Carr and Charles W. Clark
Subj-class: Other; Pattern Formation and Solitons
\\ ( http://arXiv.org/abs/cond-mat/0408491 ,  59kb)
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Paper: cond-mat/0509241
replaced with revised version Wed, 29 Mar 2006 12:44:17 GMT   (128kb)
Title: UV light-induced atom desorption for large rubidium and potassium
magneto-optical traps
Authors: C. Klempt, T. van Zoest, T. Henninger, O. Topic, E. Rasel, W. Ertmer,
and J. Arlt
Subj-class: Other
Journal-ref: Phys. Rev. A 73, 013410 (2006)
DOI: 10.1103/PhysRevA.73.013410
\\ ( http://arXiv.org/abs/cond-mat/0509241 ,  128kb)
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Paper: quant-ph/0603265
Date: Wed, 29 Mar 2006 08:00:24 GMT   (192kb)
Title: Entanglement between remote continuous variable quantum systems: effects
of transmission loss
Authors: Lars Bojer Madsen, Klaus Molmer
\\
We study the effects of losses on the entanglement created between two
separate atomic gases by optical probing and homodyne detection of the
transmitted light. The system is well-described in the Gaussian state
formulation. Analytical results quantifying the degree of entanglement between
the two gases are derived and compared with the entanglement in a pair of light
pulses generated by an EPR source. For low (high) transmission losses the
highest degree of entanglement is obtained by probing with squeezed
(antisqueezed) light. In an asymmetric setup where light is only sent one way
through the atomic samples, we find that the logarithmic negativity of
entanglement attains a constant value $-\log_2(N)$ with $N=1/3$ irrespectively
of the loss along the transmission line.
\\ ( http://arXiv.org/abs/quant-ph/0603265 ,  192kb)
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Paper: cond-mat/0603821
Date: Thu, 30 Mar 2006 16:59:44 GMT   (41kb)
Title: Finite-temperature properties of quasi-2D Bose-Einstein condensates
Authors: Kwangsik Nho and D. P. Landau
Subj-class: Statistical Mechanics
Journal-ref: Phys. Rev. A 73, 033606 (2006)
\\
Using the finite-temperature path integral Monte Carlo method, we investigate
dilute, trapped Bose gases in a quasi-two dimensional geometry. The quantum
particles have short-range, s-wave interactions described by a hard-sphere
potential whose core radius equals its corresponding scattering length. The
effect of both the temperature and the interparticle interaction on the
equilibrium properties such as the total energy, the density profile, and the
superfluid fraction is discussed. We compare our accurate results with both the
semi-classical approximation and the exact results of an ideal Bose gas. Our
results show that for repulsive interactions, (i) the minimum value of the
aspect ratio, where the system starts to behave quasi-two dimensionally,
increases as the two-body interaction strength increases, (ii) the superfluid
fraction for a quasi-2D Bose gas is distinctly different from that for both a
quasi-1D Bose gas and a true 3D system, i.e., the superfluid fraction for a
quasi-2D Bose gas decreases faster than that for a quasi-1D system and a true
3D system with increasing temperature, and shows a stronger dependence on the
interaction strength, (iii) the superfluid fraction for a quasi-2D Bose gas
lies well below the values calculated from the semi-classical approximation,
and (iv) the Kosterlitz-Thouless transition temperature decreases as the
strength of the interaction increases.
\\ ( http://arXiv.org/abs/cond-mat/0603821 ,  41kb)
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Paper: cond-mat/0507460
replaced with revised version Thu, 30 Mar 2006 15:57:12 GMT   (323kb)
Title: Stability of Bosonic atomic and molecular condensates near a Feshbach
resonance
Authors: Sourish Basu, Erich J. Mueller
Subj-class: Other
\\ ( http://arXiv.org/abs/cond-mat/0507460 ,  323kb)
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Paper: physics/0603255
Date: Thu, 30 Mar 2006 07:22:15 GMT   (880kb)
Title: Spin-Polarizing Cold Sodium Atoms in a Strong Magnetic Field
Authors: K.M.R. van der Stam, A. Kuijk, R. Meppelink, J.M. Vogels, and P. van
der Straten
Comments: 7 pages, 9 figures, submitted to Phys. Rev. A
Subj-class: Atomic Physics
\\
The efficiency of evaporative cooling, which is used for the creation of a
Bose Einstein condensate, depends strongly on the number of particles at the
start of the evaporation. A high efficiency can be reached by filling the
magneto-optical trap with a large number of atoms and subsequently transferring
these atoms to the magnetic trap as efficiently as possible. In our case (for
sodium) this efficiency is limited to 1/3, because the magnetic substates of
the F = 1 state, which is used in the trapping process, are equally populated.
This limit can be overcome by spin-polarizing the sample before the transfer.
For sodium atoms, however, the improvement is very small when it is done in a
small magnetic field due to the large number of optical transitions in