# Matt's arXiv selection: week ending 17 March 2008.

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Wed, 02 Apr 2008 08:04:28 +1000

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

Apologies for the delay... it's right in the middle of the teaching semester. A
fortnight ago there were 34 new preprints and 15 replacements.

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arXiv:0803.1116
Date: Fri, 7 Mar 2008 15:34:52 GMT (99kb)

Title: Vacancy supersolid of hard-core bosons on the square lattice
Authors: Long Dang, Massimo Boninsegni and Lode Pollet
Categories: cond-mat.stat-mech
Comments: 4 pages, 8 figures
\\
The ground state of hard-core bosons on the square lattice with nearest and
next-nearest neighbor repulsion is studied by Quantum Monte Carlo simulations.
A supersolid phase with vacancy condensation and 'star' diagonal ordering is
found for filling less than a quarter. At fillings above one quarter, a
supersolid phase exists between the star and the stripe crystal at
half-filling, with continuous phase transitions between the various phases. No
supersolid phase occurs above quarter-filling, if the ground state at
half-filling is either a checkerboard crystal or a superfluid. No commensurate
supersolid phase is observed.
\\ ( http://arxiv.org/abs/0803.1116 , 99kb)
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arXiv:0803.1125
Date: Fri, 7 Mar 2008 16:04:15 GMT (61kb)

Title: Exact Relations for a Strongly-interacting Fermi Gas from the Operator
Product Expansion
Authors: Eric Braaten, Lucas Platter
Categories: cond-mat.other
Comments: 4 pages, 2 figures
\\
The momentum distribution in a Fermi gas with two spin states and a large
scattering length has a tail that falls off like 1/k^4 at large momentum k, as
pointed out by Shina Tan. He used novel methods to derive exact relations
between the coefficient of the tail in the momentum distribution and various
other properties of the system. We present simple derivations of these
relations using the operator product expansion for quantum fields. We identify
the coefficient as the integral over space of the expectation value of a local
operator that measures the density of pairs.
\\ ( http://arxiv.org/abs/0803.1125 , 61kb)
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arXiv:0803.1140
Date: Fri, 7 Mar 2008 17:38:12 GMT (286kb)

Title: Incompressible Liquid, Stripes and Bubbles in rapidly rotating Bose
atoms at $\nu=1$
Authors: Hidetsugu Seki and Kazusumi Ino
Categories: cond-mat.mes-hall
Comments: 11 pages, 22 figures
\\
We numerically study the system of rapidly rotating Bose atoms at the filling
factor (ratio of particle number to vortex number) $\nu=1$ with the dipolar
interaction. A moderate dipolar interaction stabilizes the incompressible
quantum liquid at $\nu=1$. Further addition induces a collapse of it. The state
after the collapse is a compressible state which has phases with stripes and
bubbles.
There are two types of bubbles with a different array. We also investigate
models constructed from truncated interactions and the models with the
three-body contact interaction. They also have phases with stripes and bubbles.
\\ ( http://arxiv.org/abs/0803.1140 , 286kb)
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arXiv:0803.1167
Date: Fri, 7 Mar 2008 20:10:53 GMT (55kb)

Title: Photoassociation of a Bose-Einstein Condensate near a Feshbach Resonance
Authors: M. Junker, D. Dries, C. Welford, J. Hitchcock, Y. P. Chen and R. G.
Hulet
Categories: cond-mat.other
Comments: 5 pages, 4 figures
\\
We measure the effect of a magnetically-tuned Feshbach resonance on the rate
and light-induced frequency shift of a photoassociation resonance in ultracold
$^7$Li. The photoassociation rate constant depends strongly on magnetic field,
varying by more than a factor of 10$^4$ for fields near the Feshbach resonance.
Intensity-dependent saturation and rollover in the rate constant are observed
in a thermal gas, while saturation is observed for the first time in a
Bose-Einstein condensate. The frequency shift is also strongly field-dependent
and exhibits an anomalous blue-shift for fields just below the Feshbach
resonance.
\\ ( http://arxiv.org/abs/0803.1167 , 55kb)
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arXiv:0803.1132
Date: Fri, 7 Mar 2008 20:53:30 GMT (372kb)

Title: Dynamics of Low-Density Ultracold Rydberg Gases
Authors: J. O. Day, E. Brekke, T. G. Walker
Categories: quant-ph
Comments: 9 pages, 7 figures
\\
Population dynamics in weakly-excited clouds of ultracold $^{87}$Rb Rydberg
atoms were studied by means of trap loss, fluorescence detection, and state
dependent stimulated emission. Rydberg atoms were excited to various nl Rydberg
states via continuous two-photon excitation from a magneto-optical trap. A
stimulated emission probe laser was then used to bring the Rydberg atoms down
to the 6P$_{3/2}$ state, allowing state-dependent detection of the Rydberg
atoms. Measurements of trap loss and fluorescent emission reveal information
about the evolution of the Rydberg populations. In particular, population in
the initial Rydberg state quickly transfers to other Rydberg states by a
non-collisional mechanism, likely superradiant emission. The trap-loss
measurements are consistent with black-body ionization as the dominant loss
mechanism.
\\ ( http://arxiv.org/abs/0803.1132 , 372kb)
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arXiv:0803.1039
Date: Fri, 7 Mar 2008 09:20:05 GMT (36kb)

Title: Frequency Light Shifts Caused by the Effects of Quantization of Atomic
Motion in an Optical Lattice
Authors: A. V. Taichenachev, V. I. Yudin, V. D. Ovsiannikov, V. G. Pal'chikov
Categories: physics.atom-ph physics.optics
Comments: 4 pages,1 figure, RevTex
\\
Frequency light shifts resulting from the localization effects and effects of
the quantization of translational atomic motion in an optical lattice is
studied for a forbidden optical transition $J$=0$\to$$J$=0. In the Lamb-Dicke
regime this shift is proportional to the square root from the lattice field
intensity. With allowance made for magneto-dipole and quadrupole transitions,
the shift does not vanish at the magic wavelength, at which the linear in
intensity shift is absent. Preliminary estimates show that this shift can have
a principal significance for the lattice-based atomic clocks with accuracy of
order of 10$^{-16}-10^{-18}$. Apart from this, we find that the numerical value
of the magic frequency depends on the concrete configuration of the lattice
field and it can vary within the limits 1-100 MHz (depending on element) as one
passes from one field configuration to another. Thus, theoretical and
experimental investigations of contributions originated from magneto-dipole and
quadrupole transitions are of principal self-dependent interest.
\\ ( http://arxiv.org/abs/0803.1039 , 36kb)
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arXiv:0803.1215
Date: Sat, 8 Mar 2008 05:21:48 GMT (21kb)

Title: Fermionic ground state at unitarity and Haldane Exclusion Statistics
Authors: R.K. Bhaduri, M.V.N. Murthy and M. Brack
Categories: cond-mat.other
Comments: 4 pages, 3 figures
\\
We consider a few-particle system of trapped neutral fermionic atoms at
ultra-low temperatures, with the attractive interaction tuned to Feshbach
resonance. We calculate the energies and the spatial densities of the few-body
systems using a generalisation of the extended Thomas-Fermi (ETF) method, and
assuming the particles obey the Haldane-Wu fractional exclusion statistics
(FES) at unitarity. This method is different from the scaled ETF version given
by Chang and Bertsch (Phys. Rev. A76,021603(R) (2007)). Our semiclassical FES
results are consistent with the Monte-Carlo calculations of the above authors,
but can hardly be distinguished from their over all scaling of the ETF result
at unitarity.
\\ ( http://arxiv.org/abs/0803.1215 , 21kb)
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arXiv:0803.1341
Date: Mon, 10 Mar 2008 04:00:31 GMT (39kb)

Title: Two ultracold atoms in a completely anisotropic trap
Authors: Jun-Jun Liang, Chao Zhang
Categories: cond-mat.supr-con
Comments: 4 pages, 2 figures
Journal-ref: Phys. Scr. 77 (2008) 025302
\\
As a limiting case of ultracold atoms trapped in deep optical lattices, we
consider two interacting atoms trapped in a general anisotropic harmonic
oscillator potential, and obtain exact solutions of the Schrodinger equation
for this system. The energy spectra for different geometries of the trapping
potential are compared.
\\ ( http://arxiv.org/abs/0803.1341 , 39kb)
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arXiv:0803.1349
Date: Mon, 10 Mar 2008 06:48:37 GMT (28kb)

Title: Dynamical mean-field approximation for unitary Fermi gas
Authors: Nir Barnea
Categories: cond-mat.stat-mech
Comments: 4 pages, 3 figures
\\
Dynamical mean-field approximation with explicit pairing is utilized to study
the properties of a two-component Fermi gas at unitarity. The problem is
approximated by the lattice Hubbard Hamiltonian, and the continuum limit is
realized by diluting the lattice. We have found that at zero temperature the
predictions of this theory for the energy and the pairing gap agree remarkably
well with the results of full numerical Monte-Carlo simulations. Investigating
the evolution of the system with temperature we identify the existence of a
second order phase transition associated with a jump in the heat capacity and
the collapse of the pairing gap.
\\ ( http://arxiv.org/abs/0803.1349 , 28kb)
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arXiv:0803.1405
Date: Mon, 10 Mar 2008 13:28:40 GMT (311kb,D)

Title: Collisional Properties of p-Wave Feshbach Molecules
Authors: Yasuhisa Inada, Munekazu Horikoshi, Shuta Nakajima, Makoto
Kuwata-Gonokami, Masahito Ueda, Takashi Mukaiyama
Categories: cond-mat.other
\\
We detected the formation of p-wave Feshbach molecules for all three
combinations of the two lowest atomic spin states of 6Li. By creating a pure
molecular sample in an optical trap, we measured the inelastic collision rates
of p-wave molecules. The elastic collision rate was measured from the
thermalization rate of a breathing mode excited spontaneously upon molecular
formation.
\\ ( http://arxiv.org/abs/0803.1405 , 311kb)
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arXiv:0803.1430
Date: Mon, 10 Mar 2008 14:43:10 GMT (53kb)

Title: A dynamical theory of thermalization of composite quantum systems
Authors: Sumiyoshi Abe, A. R. Usha Devi, A. K. Rajagopal
Categories: cond-mat.stat-mech
Comments: 14 pages, no figures
\\
A quantum theoretical approach to the foundations of thermalization is
presented. This is a dynamical generalization of the kinematical approach
examined in a recent work [S. Popescu, A. J. Short, and A. Winter, Nature
Physics 2, 754 (2006)]. It is shown that a sequential application of the
dynamical interaction of the objective system with its environment, represented
by unital positive operator-valued measures, makes the system evolve to the
chaotic state. The space of the objective system is considered, in which the
system is constrained to have a given value of the fidelity. Then, the maximum
entropy principle yields a thermal state described by the canonical density
matrix. This scheme is illustrated by examples of bipartite systems. Thus, a
confluence of three principles, viz. the maximum entropy principle, unital
dynamical maps, and system-environment entanglement, play a unified role in
establishing thermalization.
\\ ( http://arxiv.org/abs/0803.1430 , 53kb)
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arXiv:0803.1229
Date: Sat, 8 Mar 2008 09:17:03 GMT (49kb)

Title: Atomic current in optical lattices: Esaki-Tsu equation revisited
Authors: Andrey R. Kolovsky
Categories: quant-ph
\\
The paper discusses the master equation approach to derivation of the
Esaki-Tsu equation for drift current. It is shown that the relaxation term in
the master equation can be identified by measuring the velocity distribution of
the carriers. We also show that the standard form of the relaxation term, used
earlier to derive Esaki-Tsu equation, predicts unphysical velocity distribution
and suggest a more elaborated relaxation term, which is argued to correctly
capture the effect of bosonic bath in experiments on atomic current in optical
lattices.
\\ ( http://arxiv.org/abs/0803.1229 , 49kb)
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arXiv:0803.1406
Date: Mon, 10 Mar 2008 13:15:38 GMT (223kb,D)

Title: Single Particle Tunneling in Strongly Driven Double Well Potentials
Authors: E. Kierig and U. Schnorrberger, A. Schietinger, J. Tomkovic, and M.K.
Oberthaler
Categories: quant-ph
Comments: 4 pages, 5 figures
\\
We report on the first direct observation of coherent control of single
particle tunneling in a strongly driven double well potential. In our setup
atoms propagate in a periodic arrangement of double wells allowing the full
control of the driving parameters such as frequency, amplitude and even the
space-time symmetry. Our experimental findings are in quantitative agreement
with the predictions of the corresponding Floquet theory and are also compared
to the predictions of a simple two mode model. Our experiments reveal directly
the critical dependence of coherent destruction of tunneling on the generalized
parity symmetry.
\\ ( http://arxiv.org/abs/0803.1406 , 223kb)
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arXiv:0803.1482
Date: Mon, 10 Mar 2008 19:56:27 GMT (429kb)

Title: Quantum States and Phases in Driven Open Quantum Systems with Cold Atoms
Authors: S. Diehl (1,2), A. Micheli (1,2), A. Kantian (1,2), B. Kraus (1,2),
H.P. B\"uchler (3), and P. Zoller (1,2) ((1) Institute for Theoretical
Physics, University of Innsbruck, Austria, (2) Institute for Quantum Optics
and Quantum Information of the Austrian Academy of Sciences, Austria, (3)
Institute for Theoretical Physics III, University of Stuttgart, Germany)
Categories: quant-ph
Comments: 9 pages, 2 figures
\\
An open quantum system, whose time evolution is governed by a master
equation, can be driven into a given pure quantum state by an appropriate
design of the system-reservoir coupling. This points out a route towards
preparing many body states and non-equilibrium quantum phases by quantum
reservoir engineering. Here we discuss in detail the example of a \emph{driven
dissipative Bose Einstein Condensate} of bosons and of paired fermions, where
atoms in an optical lattice are coupled to a bath of Bogoliubov excitations via
the atomic current representing \emph{local dissipation}. In the absence of
interactions the lattice gas is driven into a pure state with long range order.
Weak interactions lead to a weakly mixed state, which in 3D can be understood
as a depletion of the condensate, and in 1D and 2D exhibits properties
reminiscent of a Luttinger liquid or a Kosterlitz-Thouless critical phase at
finite temperature, with the role of the finite temperature'' played by the
interactions.
\\ ( http://arxiv.org/abs/0803.1482 , 429kb)
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arXiv:0710.1575 (*cross-listing*)
Date: Mon, 8 Oct 2007 15:30:12 GMT (654kb)
Date (revised v2): Mon, 3 Mar 2008 09:25:53 GMT (847kb)

Title: Probing quantum and thermal noise in an interacting many-body system
Authors: S. Hofferberth, I. Lesanovsky, T. Schumm, A. Imambekov, V. Gritsev, E.
Demler, J. Schmiedmayer
Categories: cond-mat.other quant-ph
\\
The probabilistic character of the measurement process is one of the most
puzzling and fascinating aspects of quantum mechanics. In many-body systems
quantum mechanical noise reveals non-local correlations of the underlying
many-body states. Here, we provide a complete experimental analysis of the
shot-to-shot variations of interference fringe contrast for pairs of
independently created one-dimensional Bose condensates. Analyzing different
system sizes we observe the crossover from thermal to quantum noise, reflected
in a characteristic change in the distribution functions from Poissonian to
Gumbel-type, in excellent agreement with theoretical predictions based on the
Luttinger liquid formalism. We present the first experimental observation of
quasi long-range order in one-dimensional atomic condensates, which is a
hallmark of quantum fluctuations in one-dimensional systems. Furthermore, our
experiments constitute the first analysis of the full distribution of quantum
noise in an interacting many-body system.
\\ ( http://arxiv.org/abs/0710.1575 , 847kb)
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arXiv:0802.0386 (*cross-listing*)
Date: Mon, 4 Feb 2008 11:32:54 GMT (280kb)

Title: Long-Range Order in Electronic Transport through Disordered Metal Films
Authors: S. Aigner, L. Della Pietra, Y. Japha, O. Entin-Wohlman, T. David, R.
Salem, R. Folman, J. Schmiedmayer
Categories: cond-mat.mtrl-sci cond-mat.other quant-ph
Journal-ref: Science 319, 1226 - 1229, (2008)
DOI: 10.1126/science.1152458
\\
Ultracold atom magnetic field microscopy enables the probing of current flow
patterns in planar structures with unprecedented sensitivity. In
polycrystalline metal (gold) films we observe long-range correlations forming
organized patterns oriented at +/- 45 deg relative to the mean current flow,
even at room temperature and at length scales orders of magnitude larger than
the diffusion length or the grain size. The preference to form patterns at
these angles is a direct consequence of universal scattering properties at
defects. The observed amplitude of the current direction fluctuations scales
inversely to that expected from the relative thickness variations, the grain
size and the defect concentration, all determined independently by standard
methods. This indicates that ultracold atom magnetometry enables new insight
into the interplay between disorder and transport.
\\ ( http://arxiv.org/abs/0802.0386 , 280kb)
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arXiv:0803.1498
Date: Mon, 10 Mar 2008 20:41:38 GMT (18kb)

Title: Evolution from BCS to BKT superfluidity in one-dimensional optical
lattices
Authors: M. Iskin and C. A. R. S \'a de Melo
Categories: cond-mat.supr-con cond-mat.other
Comments: 4 pages with 2 figures
\\
We analyze the finite temperature phase diagram of fermion mixtures in
one-dimensional optical lattices as a function of interaction strength. At low
temperatures, the system evolves from an anisotropic three-dimensional
Bardeen-Cooper-Schrieffer (BCS) superfluid to an effectively two-dimensional
Berezinskii-Kosterlitz-Thouless (BKT) superfluid as the interaction strength
increases. We calculate the critical temperature as a function of interaction
strength, and identify the region where the dimensional crossover occurs for a
specified optical lattice potential. Finally, we show that the dominant vortex
excitations near the critical temperature evolve from multiplane elliptical
vortex loops in the three-dimensional regime to planar vortex-antivortex pairs
in the two-dimensional regime, and we propose a detection scheme for these
excitations.
\\ ( http://arxiv.org/abs/0803.1498 , 18kb)
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arXiv:0803.1503
Date: Mon, 10 Mar 2008 21:57:31 GMT (59kb)

Title: Variational HFB Equations in the Thomas-Fermi Limit for Ultracold
Trapped Gases
Authors: M. Benarous
Categories: cond-mat.stat-mech
Comments: 16 pages, 6 figures
\\
We derive variationally the HFB equations for a trapped self-interacting Bose
gas at finite temperature. In the Thomas-Fermi limit, we obtain simple
expressions for the condensate, the non condensate and the anomalous densities.
Their behavior in terms of the condensate fraction meets qualitatively the
experimental data. In particular, the non condensate and the anomalous
densities are peaked at the center of the trap and not at the edges as
predicted by the self-consistent HFB calculations.
\\ ( http://arxiv.org/abs/0803.1503 , 59kb)
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arXiv:0803.1548
Date: Tue, 11 Mar 2008 10:13:45 GMT (519kb)

Title: Adiabatic Loading of Cold Bosons in Three-Dimensional Optical Lattices
and Superfluid-Normal Phase Transition
Authors: S. Yoshimura, S. Konabe, and T. Nikuni
Categories: cond-mat.other
Comments: 4 pages, 8 figures
\\
We investigate the effects of the adiabatic loading of optical lattices to
the temperature by applying the mean-field approximation to the
three-dimensional Bose-Hubbard model at finite temperatures. We compute the
lattice-height dependence of the isentropic curves for the given initial
temperatures in case of the homogeneous system i.e., neglecting the trapping
potential. Taking the unit of temperatures as the recoil energy, the adiabatic
cooling/heating through superfluid (SF) - normal (N) phase transition is
clearly understood. It is found that the cooling occurs in SF phase while the
heating occurs in N phase and the efficiency of adibatic cooling/heating is
higher at higher temperatures. We also explain how its behavior can be
understood from the lattice-hight dependence of dispersion relation in each
phase. Furthermore, the connection of the adiabatic heating/cooling between the
cases with/without the trapping potential is discussed.
\\ ( http://arxiv.org/abs/0803.1548 , 519kb)
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arXiv:0803.1647
Date: Tue, 11 Mar 2008 18:29:27 GMT (7kb)

Title: Virial theorem for confined universal Fermi gases
Authors: J. E. Thomas
Categories: cond-mat.stat-mech cond-mat.other
\\
Optically-trapped two-component Fermi gases near a broad Feshbach resonance
exhibit universal thermodynamics, where the properties of the gas are
independent of the details of the two-body scattering interactions. We present
a global proof that such a universal gas obeys the virial theorem for {\it any}
trapping potential $U$ and any spin mixture, without assuming either the local
density approximation or harmonic confinement. The total energy of the gas is
given in scale invariant form by $E=<\epsilon\partial U/\partial\epsilon>$,
where $\epsilon$ is an {\it arbitrary} energy scale in terms of which all
length and energy scales that appear in the confining potential are written.
This result enables model-independent energy measurement in traps that are
anharmonic as well as anisotropic by observing only the cloud profile, and
provides a consistency check for many-body calculations in the universal
regime.
\\ ( http://arxiv.org/abs/0803.1647 , 7kb)
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arXiv:0803.1280 (*cross-listing*)
Date: Sun, 9 Mar 2008 15:10:28 GMT (723kb)

Title: The ground state energy at unitarity
Authors: Dean Lee (North Carolina State University)
Categories: nucl-th cond-mat.other hep-lat
Comments: 27 pages, 9 figures
\\
We consider two-component fermions on the lattice in the unitarity limit.
This is an idealized limit of attractive fermions where the range of the
interaction is zero and the scattering length is infinite. Using Euclidean time
projection, we compute the ground state energy using four computationally
different but physically identical auxiliary-field methods. The best
performance is obtained using a bounded continuous auxiliary field and a
non-local updating algorithm called hybrid Monte Carlo. With this method we
calculate results for 10 and 14 fermions at lattice volumes 4^3, 5^3, 6^3, 7^3,
8^3 and extrapolate to the continuum limit. For 10 fermions in a periodic cube,
the ground state energy is 0.292(12) times the ground state energy for
non-interacting fermions. For 14 fermions the ratio is 0.329(5).
\\ ( http://arxiv.org/abs/0803.1280 , 723kb)
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arXiv:0803.1478 (*cross-listing*)
Date: Mon, 10 Mar 2008 19:21:51 GMT (19kb)

Title: Measurement-based quantum computer in the gapped ground state of a
two-body Hamiltonian
Authors: Gavin K. Brennen, Akimasa Miyake
Categories: quant-ph cond-mat.other
Comments: 5 pages, 1 figure
\\
We propose a scheme of the ground-code measurement-based quantum computer,
which enjoys two major advantages. (i) Every logical qubit is encoded in the
gapped degenerate ground subspace of a spin-1 chain with nearest-neighbor
two-body interactions, so that it equips built-in robustness against noise.
(ii) Computation is processed by single-spin measurements along multiple chains
dynamically coupled on demand, so as to keep teleporting only logical
information into a gap-protected ground state of the rest chains after the
interactions with spins to be measured are adiabatically turned off. We
describe implementations using trapped atoms or polar molecules in an optical
lattice, where the gap is expected to be as large as 0.2 KHz or 4.8 KHz
respectively.
\\ ( http://arxiv.org/abs/0803.1478 , 19kb)
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arXiv:0803.1499
Date: Mon, 10 Mar 2008 21:11:52 GMT (42kb)

Title: Multipartite Entanglement in Non-Equilibrium Quantum Phase Transition in
a Collective Atomic System
Authors: Kishore T. Kapale and Girish S. Agarwal
Categories: quant-ph
Comments: 4 pages, 7 figures
\\
We study multipartite entanglement in non-equilibrium quantum phase
transition (NEQPT) attainable in a coherently driven atomic ensemble undergoing
collective decay. The NEQPT arises in the steady state of the system as the
drive field strength is varied in comparison with the decay parameter. A close
connection is observed between the critical behavior and the multi-partite
entanglement in the system determined via the von Neumann entropy. The
derivative of the von Neumann entropy shows Lambda-type behavior typical of the
second order phase transitions. We further show that the calculated bi- and
tri- partite entropies satisfy the Lieb inequality.
\\ ( http://arxiv.org/abs/0803.1499 , 42kb)
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arXiv:0803.1643
Date: Tue, 11 Mar 2008 18:38:16 GMT (815kb,D)

Title: Quantum Many-Body Dynamics of Coupled Double-Well Superlattices
Authors: Peter Barmettler, Ana Maria Rey, Eugene Demler, Mikhail D. Lukin,
Immanuel Bloch, Vladimir Gritsev
Categories: quant-ph
Comments: 13 pages, 10 figures
\\
We propose a method for controllable generation of non-local entangled pairs
using spinor atoms loaded in an optical superlattice. Our scheme iteratively
increases the distance between entangled atoms by controlling the coupling
between the double wells. When implemented in a finite linear chain of 2N
atoms, it creates a triplet valence bond state with large persistency of
entanglement (of the order of N). We also study the non-equilibrium dynamics of
the one-dimensional ferromagnetic Heisenberg Hamiltonian and show that the time
evolution of a state of decoupled triplets on each double well leads to the
formation of a highly entangled state where short-distance antiferromagnetic
correlations coexist with longer-distance ferromagnetic ones. We present
methods for detection and characterization of the various dynamically generated
states. These ideas are a step forward towards the use of atoms trapped by
light as quantum information processors and quantum simulators.
\\ ( http://arxiv.org/abs/0803.1643 , 815kb)
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arXiv:0803.1774
Date: Wed, 12 Mar 2008 14:00:12 GMT (272kb)

Title: Disorder-induced trapping versus Anderson localization in Bose-Einstein
condensates expanding in disordered potentials
Authors: Laurent Sanchez-Palencia (LCFIO), David Cl\'ement (LCFIO), Pierre
Lugan (LCFIO), Philippe Bouyer (LCFIO), Alain Aspect (LCFIO)
Categories: cond-mat.other
Comments: To appear in the New Journal of Physics; focus issue "Quantum
Correlations in Tailored Matter - Common perspectives of mesoscopic systems
and quantum gases"; 30 pages, 10 figures
Proxy: ccsd hal-00263549
\\
We theoretically investigate the localization of an expanding Bose-Einstein
condensate with repulsive atom-atom interactions in a disordered potential. We
focus on the regime where the initial inter-atomic interactions dominate over
the kinetic energy and the disorder. At equilibrium in a trapping potential and
for small disorder, the condensate shows a Thomas-Fermi shape modified by the
disorder. When the condensate is released from the trap, a strong suppression
of the expansion is obtained in contrast to the situation in a periodic
potential with similar characteristics. This effect crucially depends on both
the momentum distribution of the expanding BEC and the strength of the
disorder. For strong disorder, the suppression of the expansion results from
the fragmentation of the core of the condensate and from classical reflections
from large modulations of the disordered potential in the tails of the
condensate. We identify the corresponding disorder-induced trapping scenario
for which large atom-atom interactions and strong reflections from single
modulations of the disordered potential play central roles. For weak disorder,
the suppression of the expansion signals the onset of Anderson localization,
which is due to multiple scattering from the modulations of the disordered
potential. We compute analytically the localized density profile of the
condensate and show that the localization crucially depends on the correlation
function of the disorder. In particular, for speckle potentials the long-range
correlations induce an effective mobility edge in 1D finite systems. Numerical
calculations performed in the mean-field approximation support our analysis for
both strong and weak disorder.
\\ ( http://arxiv.org/abs/0803.1774 , 272kb)
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arXiv:0803.1482 (*cross-listing*)
Date: Mon, 10 Mar 2008 19:56:27 GMT (429kb)

Title: Quantum States and Phases in Driven Open Quantum Systems with Cold Atoms
Authors: S. Diehl (1,2), A. Micheli (1,2), A. Kantian (1,2), B. Kraus (1,2),
H.P. B\"uchler (3), and P. Zoller (1,2) ((1) Institute for Theoretical
Physics, University of Innsbruck, Austria, (2) Institute for Quantum Optics
and Quantum Information of the Austrian Academy of Sciences, Austria, (3)
Institute for Theoretical Physics III, University of Stuttgart, Germany)
Categories: quant-ph cond-mat.stat-mech cond-mat.str-el
Comments: 9 pages, 2 figures
\\
An open quantum system, whose time evolution is governed by a master
equation, can be driven into a given pure quantum state by an appropriate
design of the system-reservoir coupling. This points out a route towards
preparing many body states and non-equilibrium quantum phases by quantum
reservoir engineering. Here we discuss in detail the example of a \emph{driven
dissipative Bose Einstein Condensate} of bosons and of paired fermions, where
atoms in an optical lattice are coupled to a bath of Bogoliubov excitations via
the atomic current representing \emph{local dissipation}. In the absence of
interactions the lattice gas is driven into a pure state with long range order.
Weak interactions lead to a weakly mixed state, which in 3D can be understood
as a depletion of the condensate, and in 1D and 2D exhibits properties
reminiscent of a Luttinger liquid or a Kosterlitz-Thouless critical phase at
finite temperature, with the role of the finite temperature'' played by the
interactions.
\\ ( http://arxiv.org/abs/0803.1482 , 429kb)
------------------------------------------------------------------------------
\\
arXiv:0803.1665
Date: Tue, 11 Mar 2008 20:06:39 GMT (318kb)

Title: Many body effects and cluster state quantum computation in strongly
interacting systems of photons
Authors: Dimitris G. Angelakis, Sougato Bose, Alastair Kay, Marcelo F. Santos
Categories: quant-ph
Comments: 10 pages. Contribution to proceedings of "Quantum Information and
Many-Body Quantum Systems" Workshop, 26-31 Mar 2007, Pisa
\\
We discuss the basic properties of a recently proposed hybrid light-matter
system of strongly interacting photons in an array of coupled cavities each
doped with a single two level system. Using the non-linearity generated from
the photon blockade effect, we predict strong correlations between the hopping
photons in the array, and show the possibility of observing a phase transition
from a polaritonic insulator to a superfluid of photons. In the Mott phase,
this interaction can be mapped to an array of spins. We show how the remaining
Hamiltonian, in conjunction with individual spin manipulation, can thus be used
for simulating spin chains (useful for state transfer protocols) and cluster
state quantum computation.
\\ ( http://arxiv.org/abs/0803.1665 , 318kb)
------------------------------------------------------------------------------
\\
arXiv:0803.1760
Date: Wed, 12 Mar 2008 12:36:15 GMT (23kb)

Title: Entanglement of two distant Bose-Einstein condensates by detection of
Bragg-scattered photons
Authors: B. Deb and G. S. Agarwal
Categories: quant-ph
Comments: 8 pages, 7 figures
\\
We show that it is possible to entangle two distant Bose-Einstein condensates
by detection of Hanbury Brown-Twiss type correlations in photons
Bragg-scattered by the condensates. The generated entanglement is either in
quasiparticle number or quadrature phase variables. We present selective
results which exhibit complementary squeezing behavior in relative
quasi-particle number and phase operators. Our proposed scheme can be
generalized for multiple condensates and also for spinor condensates with Bragg
scattering of polarized light with the latter capable of producing hyper
entanglement.
\\ ( http://arxiv.org/abs/0803.1760 , 23kb)
------------------------------------------------------------------------------
\\
arXiv:0803.1799
Date: Wed, 12 Mar 2008 16:51:14 GMT (82kb)

Title: Dynamics and stability of Bose-Einstein condensates with attractive 1/r
interaction
Authors: Holger Cartarius, Toma\v{z} Fab\v{c}i\v{c}, J\"org Main, G\"unter
Wunner
Categories: quant-ph
Comments: 12 pages, 12 figures
\\
The time-dependent extended Gross-Pitaevskii equation for Bose-Einstein
condensates with attractive 1/r interaction is investigated with both a
variational approach and numerically exact calculations. We show that these
condensates exhibit signatures known from the nonlinear dynamics of autonomous
Hamiltonian systems. The two stationary solutions created in a tangent
bifurcation at a critical value of the scattering length are identified as
elliptical and hyperbolical fixed points, corresponding to stable and unstable
stationary states of the condensate. The stable stationary state is surrounded
by elliptical islands, corresponding to condensates periodically oscillating in
time, whereas condensate wave functions in the unstable region undergo a
collapse within finite time. For negative scattering lengths below the tangent
bifurcation no stationary solutions exist, i.e., the condensate is always
unstable and collapses.
\\ ( http://arxiv.org/abs/0803.1799 , 82kb)
------------------------------------------------------------------------------
\\
arXiv:0803.1810
Date: Wed, 12 Mar 2008 16:40:44 GMT (146kb)

Title: Entanglement Swapping with Storage and Retrieval of Light: A Building
Block of Quantum Repeaters
Authors: Zhen-Sheng Yuan, Yu-Ao Chen, Bo Zhao, Shuai Chen, Joerg Schmiedmayer,
Jian-Wei Pan
Categories: quant-ph
Comments: 18 pages, 4 figures
\\
Here we report on the realization of a key element of a quantum repeater:
Entanglement connection between two remote stored atomic qubits mediated by two
photon interference and the transfer of the stored entanglement back to photon
for further transmission. In the experiment, two atomic ensembles, each
entangled with a single photon they emit, are projected into an entangled state
by performing a joint Bell state measurement on the two single photons after
passing through a 300 m long fiber-based communication channel. The
entanglement is stored and later mapped back onto two photons whose
entanglement is verified by the violation of Bell's inequality or by an
entanglement witness. Our method is intrinsically phase insensitive and
establishes the essential element to realize quantum repeaters with stationary
atomic qubits as quantum memories and flying photonic qubits as quantum
messengers.
\\ ( http://arxiv.org/abs/0803.1810 , 146kb)
------------------------------------------------------------------------------

\\
arXiv:0803.1889
Date: Thu, 13 Mar 2008 03:48:41 GMT (120kb)

Title: Atom-Pair Tunneling in Optical Lattices Beyond the Bose-Hubbard Model
Authors: J.-Q. Liang, J.-L. Liu, W.-D. Li, Z.-J. Li
Categories: cond-mat.other
\\
We demonstrate that the Bose-Hubbard model of ultracold spinless atoms in
strongly interacting regime should be extended to include the two-body
interaction of nearest neighbors.. An atom-pair tunneling term appeared
naturally in the extended model, which leads to essentially no effect in the
weak interaction limit, plays a crucial role in the strong atom-atom
interaction regime. The tunneling dynamics of two-atom occupation in a
double-well trap is studied in terms of both the Bose-Hubbard and extended
Hamiltonians showing significant difference and the later results in a good
agreement with the experimental observation of atom-pair tunneling.
\\ ( http://arxiv.org/abs/0803.1889 , 120kb)
------------------------------------------------------------------------------
\\
arXiv:0803.2015
Date: Thu, 13 Mar 2008 17:37:48 GMT (684kb)

Title: Noise correlation spectroscopy of the broken order of a Mott insulating
phase
Authors: V. Guarrera, N. Fabbri, L. Fallani, C. Fort, K. M. R. van der Stam,
and M. Inguscio
Categories: cond-mat.other
\\
We use a two-color lattice to break the homogeneous site occupation of an
atomic Mott Insulator of bosonic 87Rb. We detect the disruption of the ordered
Mott domains via noise correlation analysis of the atomic density distribution
after time-of-flight. The appearance of additional correlation peaks evidences
the redistribution of the atoms into a strongly inhomogeneous insulating state,
in quantitative agreement with the predictions.
\\ ( http://arxiv.org/abs/0803.2015 , 684kb)
------------------------------------------------------------------------------
\\
arXiv:0803.1501 (*cross-listing*)
Date: Mon, 10 Mar 2008 21:38:20 GMT (230kb)

Title: Self-consistent crystalline condensate in chiral Gross-Neveu and
Bogoliubov-de Gennes systems
Authors: Gokce Basar and Gerald V. Dunne
Categories: hep-th cond-mat.supr-con hep-lat hep-ph quant-ph
Comments: 5 pages, 5 figures
\\
We derive a new exact self-consistent crystalline condensate in the 1+1
dimensional chiral Gross-Neveu model. This also yields a new exact crystalline
solution for the one dimensional Bogoliubov-de Gennes equations and the
Eilenberger equation of semiclassical superconductivity. We show that the
functional gap equation can be reduced to a solvable nonlinear equation, and
discuss implications for the temperature-chemical potential phase diagram.
\\ ( http://arxiv.org/abs/0803.1501 , 230kb)
------------------------------------------------------------------------------
\\
arXiv:0803.1887
Date: Thu, 13 Mar 2008 03:45:17 GMT (54kb)

Title: Hybrid phase-space simulation method for interacting Bose fields
Authors: Scott E. Hoffmann, Joel F. Corney and Peter D. Drummond
Categories: quant-ph
Comments: 13 pages; 6 figures
\\
We introduce an approximate phase-space technique to simulate the quantum
dynamics of interacting bosons. With the future goal of treating Bose-Einstein
condensate systems, the method is designed for systems with a natural
separation into highly occupied (condensed) modes and lightly occupied modes.
The method self-consistently uses the Wigner representation to treat highly
occupied modes and the positive-P representation for lightly occupied modes. In
this method, truncation of higher-derivative terms from the Fokker-Planck
equation is usually necessary. However, at least in the cases investigated
here, the resulting systematic error, over a finite time, vanishes in the limit
of large Wigner occupation numbers. We tested the method on a system of two
interacting anharmonic oscillators, with high and low occupations,
respectively. The Hybrid method successfully predicted atomic quadratures to a
useful simulation time 60 times longer than that of the positive-P method. The
truncated Wigner method also performed well in this test. For the prediction of
the correlation in a quantum nondemolition measurement scheme, for this same
system, the Hybrid method gave excellent agreement with the exact result, while
the truncated Wigner method showed a large systematic error.
\\ ( http://arxiv.org/abs/0803.1887 , 54kb)
------------------------------------------------------------------------------

The replacements:

------------------------------------------------------------------------------
\\
arXiv:0803.0059
Date: Sat, 1 Mar 2008 11:13:43 GMT (454kb)
Date (revised v2): Tue, 4 Mar 2008 09:14:59 GMT (469kb)

Title: Probing Mott lobes via the AC Josephson effect
Authors: M.X. Huo, Ying Li, Z. Song and C.P. Sun
Categories: quant-ph cond-mat.str-el
Comments: 5 pages, 4 figures
\\
The alternating-current (AC) Josephson effect is studied in a system
consisting of two weakly coupled Bose Hubbard models. In the framework of the
mean field theory, Gross-Pitaevskii equations show that the amplitude of the
Josephson current is proportional to the product of superfluid order
parameters. In addition, the chemical potential--current relation for a small
size system is obtained via the exact numerical computation. This allows us to
propose a feasible experimental scheme to measure the Mott lobes of the quantum
phase transition.
\\ ( http://arxiv.org/abs/0803.0059 , 469kb)
------------------------------------------------------------------------------
\\
arXiv:0704.3906
replaced with revised version Mon, 10 Mar 2008 18:24:31 GMT (64kb)

Title: Area laws in quantum systems: mutual information and correlations
Authors: M.M. Wolf, F. Verstraete, M.B. Hastings, J.I. Cirac
Categories: quant-ph cond-mat.stat-mech
Comments: 5 pages, 2 figures, published version with appendix
Journal-ref: Phys. Rev. Lett. 100, 070502 (2008)
\\ ( http://arxiv.org/abs/0704.3906 , 64kb)
------------------------------------------------------------------------------
\\
arXiv:0706.3879
replaced with revised version Mon, 10 Mar 2008 03:22:38 GMT (130kb)

Title: Coherent Quantum Optical Control with Subwavelength Resolution
Authors: Alexey V. Gorshkov, Liang Jiang, Markus Greiner, Peter Zoller, and
Mikhail D. Lukin
Categories: quant-ph cond-mat.mes-hall cond-mat.other
Comments: 4 pages, 2 figures. V2: changes in presentation (text, figures,
tables) and new references - final version as published in Phys. Rev. Lett.
Journal-ref: Phys. Rev. Lett. 100, 093005 (2008)
DOI: 10.1103/PhysRevLett.100.093005
\\ ( http://arxiv.org/abs/0706.3879 , 130kb)
------------------------------------------------------------------------------
\\
arXiv:0708.3241
replaced with revised version Mon, 10 Mar 2008 19:43:56 GMT (148kb)

Title: Supersolid Bose-Fermi Mixtures in Optical Lattices
Authors: I. Titvinidze, M. Snoek, W. Hofstetter
Categories: cond-mat.other
Comments: 4 pages, 5 pictures, Published version
Journal-ref: Phys. Rev. lett. 100, 100401 (2008)
DOI: 10.1103/PhysRevLett.100.100401
\\ ( http://arxiv.org/abs/0708.3241 , 148kb)
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\\
arXiv:0711.3015
replaced with revised version Sun, 9 Mar 2008 10:22:21 GMT (534kb,D)

Title: Quantum magnetism and criticality
Authors: Subir Sachdev
Categories: cond-mat.str-el cond-mat.supr-con hep-th quant-ph
Comments: 39 pages, 10 figures, review article for non-specialists; (v2) added
clarifications and references; (v3) minor corrections; (v4) added footnote on
hydrodynamic long-time tails
Journal-ref: Nature Physics 4, 173 (2008)
DOI: 10.1038/nphys894
\\ ( http://arxiv.org/abs/0711.3015 , 534kb)
------------------------------------------------------------------------------
\\
arXiv:0802.3158
replaced with revised version Mon, 10 Mar 2008 17:48:40 GMT (59kb)

Title: Probing ultra-cold Fermi atoms with a single ion
Authors: Y. Sherkunov, B. Muzykantskii, N. d'Ambrumenil, B.D Simons
Categories: cond-mat.str-el
Comments: 4 pages, 2 figures
\\ ( http://arxiv.org/abs/0802.3158 , 59kb)
------------------------------------------------------------------------------
\\
arXiv:0803.0846
replaced with revised version Mon, 10 Mar 2008 10:47:03 GMT (520kb)

Title: Ground State Properties of a Tonks-Girardeau Gas in a Split Trap
Authors: J. Goold and Th. Busch
Categories: cond-mat.other quant-ph
Comments: 7 pages, 9 figures
\\ ( http://arxiv.org/abs/0803.0846 , 520kb)
-----------------------------------------------------------------------------
\\
arXiv:0706.3879
replaced with revised version Mon, 10 Mar 2008 03:22:38 GMT (130kb)

Title: Coherent Quantum Optical Control with Subwavelength Resolution
Authors: Alexey V. Gorshkov, Liang Jiang, Markus Greiner, Peter Zoller, and
Mikhail D. Lukin
Categories: quant-ph cond-mat.mes-hall cond-mat.other
Comments: 4 pages, 2 figures. V2: changes in presentation (text, figures,
tables) and new references - final version as published in Phys. Rev. Lett.
Journal-ref: Phys. Rev. Lett. 100, 093005 (2008)
DOI: 10.1103/PhysRevLett.100.093005
\\ ( http://arxiv.org/abs/0706.3879 , 130kb)
------------------------------------------------------------------------------
\\
arXiv:0706.0839
replaced with revised version Tue, 11 Mar 2008 12:39:03 GMT (166kb)

Title: Correlated bosons on a lattice: Dynamical mean-field theory for
Bose-Einstein condensed and normal phases
Authors: Krzysztof Byczuk and Dieter Vollhardt
Categories: cond-mat.other quant-ph
Comments: 17 pages, 4 figures, extended version
\\ ( http://arxiv.org/abs/0706.0839 , 166kb)
------------------------------------------------------------------------------
\\
arXiv:0710.1213
replaced with revised version Tue, 11 Mar 2008 13:36:21 GMT (117kb)

Title: Exploiting soliton decay and phase fluctuations in atom chip
interferometry of Bose-Einstein condensates
Authors: R.G. Scott, T.E. Judd, T.M. Fromhold
Categories: cond-mat.other
Comments: 5 pages, 5 figures
\\ ( http://arxiv.org/abs/0710.1213 , 117kb)
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\\
arXiv:0710.4493
replaced with revised version Tue, 11 Mar 2008 16:55:41 GMT (631kb)

Title: Transport of strong-coupling polarons in optical lattices
Authors: M. Bruderer, A. Klein, S. R. Clark, D. Jaksch
Categories: quant-ph
Comments: 25 pages, 6 figures
Journal-ref: New J. Phys. 10, 033015 (2008)
DOI: 10.1088/1367-2630/10/3/033015
\\ ( http://arxiv.org/abs/0710.4493 , 631kb)
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\\
arXiv:0706.4434
replaced with revised version Wed, 12 Mar 2008 09:52:21 GMT (75kb)

Title: Pairing of 1D Bose-Fermi mixtures with unequal masses
Authors: M. Rizzi, A. Imambekov
Categories: cond-mat.str-el cond-mat.other
Comments: 7 pages, 5 figures
Journal-ref: Phys. Rev. A 77, 023621 (2008) (6 pages)
DOI: 10.1103/PhysRevA.77.023621
\\ ( http://arxiv.org/abs/0706.4434 , 75kb)
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\\
arXiv:0803.1405
replaced with revised version Wed, 12 Mar 2008 04:10:59 GMT (311kb,D)

Title: Collisional Properties of p-Wave Feshbach Molecules
Authors: Yasuhisa Inada, Munekazu Horikoshi, Shuta Nakajima, Makoto
Kuwata-Gonokami, Masahito Ueda, Takashi Mukaiyama
Categories: cond-mat.other
\\ ( http://arxiv.org/abs/0803.1405 , 311kb)
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\\
arXiv:0711.3006 (*cross-listing*)
replaced with revised version Wed, 12 Mar 2008 20:56:08 GMT (24kb,D)

Title: Strongly paired fermions: Cold atoms and neutron matter
Authors: Alexandros Gezerlis and J. Carlson
Categories: nucl-th cond-mat.other
Comments: 5 pages, 4 figures; 3 references added; v2 corresponds to the
published version
Report-no: LA-UR-07-7894
Journal-ref: Phys. Rev. C 77, 032801(R) (2008)
DOI: 10.1103/PhysRevC.77.032801
\\ ( http://arxiv.org/abs/0711.3006 , 24kb)
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\\
arXiv:0803.1430
replaced with revised version Thu, 13 Mar 2008 14:39:20 GMT (54kb)

Title: A dynamical theory of thermalization in composite quantum systems
Authors: Sumiyoshi Abe, A. R. Usha Devi, A. K. Rajagopal
Categories: cond-mat.stat-mech quant-ph
Comments: 14 pages, no figures. The title slightly changed
\\ ( http://arxiv.org/abs/0803.1430 , 54kb)
-----------------------------------------------------------------------------

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 Apr 02 2008 - 09:39:35 EST

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