[Matts-arxiv] Matt's arXiv selection: week ending 25 September 2009

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Thu, 05 Nov 2009 20:48:07 +1000

Dear subscribers,

This week's email was collated by Mike Garrett. There are 32 new preprints and
17 replacements.

Date: Fri, 18 Sep 2009 06:03:31 GMT (104kb)

Title: Reentrance of Bose-Einstein condensation in spinor atomic gases in
   magnetic field
Authors: Chengjun Tao, Zhirong Jiao, and Qiang Gu
Categories: cond-mat.quant-gas cond-mat.supr-con
Comments: 6 pages, 6 figures
   We calculate the Bose-Einstein condensation (BEC) temperature of spin-1
atomic bosons in external magnetic field, taking into account the influence of
the quadratic Zeeman effect. In case that the quadratic Zeeman coefficient is
positive, the BEC temperature exhibits a nontrivial dependance on the magnetic
field and a magnetic-field-induced reentrant phenomenon of BEC is observed.
This phenomenon could be well understood by the competition between the linear
and quadratic Zeeman effects. Reentrance of BEC in a trapped spinor Bose gas is
also discussed.
\\ ( http://arxiv.org/abs/0909.3357 , 104kb)
Date: Fri, 18 Sep 2009 14:55:58 GMT (304kb,D)

Title: Sound propagation in a Bose-Einstein condensate at finite temperatures
Authors: R. Meppelink, S.B. Koller, and P. van der Straten
Categories: cond-mat.quant-gas
   We study the propagation of a density wave in a magnetically trapped
Bose-Einstein condensate at finite temperatures. The thermal cloud is in the
hydrodynamic regime and the system is therefore described by the two-fluid
model. A phase-contrast imaging technique is used to image the cloud of atoms
and allows us to observe small density excitations. The propagation of the
density wave in the condensate is used to determine the speed of sound as a
function of the temperature. We find the speed of sound to be in good agreement
with calculations based on the Landau two-fluid model.
\\ ( http://arxiv.org/abs/0909.3455 , 304kb)
Date: Fri, 18 Sep 2009 18:51:10 GMT (386kb)

Title: Metastable states and macroscopic quantum tunneling in a cold atom
   Josephson ring
Authors: Dmitry Solenov, Dmitry Mozyrsky
Categories: cond-mat.quant-gas
Comments: 4 pages, 2 figures
   We study macroscopic properties of a system of weakly interacting neutral
bosons confined in a ring-shaped potential with a Josephson junction. We derive
an effective low energy action for this system and evaluate its properties. In
particular we find that the system possesses a set of metastable
current-carrying states and evaluate the rates of transitions between these
states due to macroscopic quantum tunneling. Finally we discuss signatures of
different metastable states in the time-of-flight images and argue that the
effect is observable within currently available experimental technique.
\\ ( http://arxiv.org/abs/0909.3501 , 386kb)
Date: Thu, 17 Sep 2009 21:32:10 GMT (1024kb)

Title: Analytic Approximation of the Tavis-Cummings Ground State via Projected
Authors: Octavio Castanos, Eduardo Nahmad-Achar, Ramon Lopez-Pena, and Jorge G.
Categories: quant-ph
Comments: 22 pages, 13 figures, accepted for publication in Physics Scripta
   We show that an excellent approximation to the exact quantum solution of the
ground state of the Tavis-Cummings model is obtained by means of a
semi-classical projected state. This state has an analytical form in terms of
the model parameters and, in contrast to the exact quantum state, it allows for
an analytical calculation of the expectation values of field and matter
observables, entanglement entropy between field and matter, squeezing
parameter, and population probability distributions. The fidelity between this
projected state and the exact quantum ground state is very close to 1, except
for the region of classical phase transitions. We compare the analytical
results with those of the exact solution obtained through the direct
Hamiltonian diagonalization as a function of the atomic separation energy and
the matter-field coupling.
\\ ( http://arxiv.org/abs/0909.3322 , 1024kb)
Date: Fri, 18 Sep 2009 13:18:22 GMT (619kb)

Title: Towards Bose-Einstein condensation of excitons in an asymmetric
   multi-quantum state magnetic lattice
Authors: A. Abdelrahman, M. Vasiliev, K. Alameh, P. Hannaford, Byoung S. Ham,
   and Yong-Tak Lee
Categories: quant-ph cond-mat.quant-gas
Comments: Conference Paper: NUSOD 2009
   An asymmetric multi-quantum state magnetic lattice is proposed to host
excitons formed in a quantum degenerate gas of ultracold fermionic atoms to
simulate Bose-Einstein condensation (BEC) of excitons. A Quasi-two dimensional
degenerate gas of excitons can be collected in the in-plane asymmetric magnetic
bands created at the surface of the proposed magnetic lattice, where the
ultracold fermions simulate separately direct and indirect confined
electronhole pairs (spin up fermions-spin down fermions) rising to the
statistically degenerate Bose gas and eventually through controlled tunnelling
to BEC of excitons. The confinement of the coupled magnetic quantum well
(CMQWs) system may significantly improve the condition for long lived exciton
BEC. The exciton BEC, formed in CMQWs can be regarded as a suitable host for
the multi-qubits (multipartite) systems to be used in quantum information
\\ ( http://arxiv.org/abs/0909.3430 , 619kb)
Date: Fri, 18 Sep 2009 13:30:41 GMT (543kb)

Title: Multipartite Entanglement in a Discrete Magnetic Bands Magnetic Lattice
Authors: A. Abdelrahman, P. Hannaford, M. Vasiliev and K. Alameh
Categories: quant-ph
Comments: Conference Paper:Asia Communications and Photonics Conference and
   Exhibition (ACP)
   Using magneto-optical materials, an asymmetric multi-quantum state magnetic
lattice is proposed to host an entangled multipartite system formed by using a
quantum degenerate gas of ultracold atoms in a Bose Einstein Condensate (BEC).
The discrete magnetic bands magnetic lattice is devised to locate a
controllable long-range entanglement of a many harmonic oscillator system well
separated in space. The confinement of the coupled magnetic quantum well (CMQW)
system may significantly improve the condition for the long-range entanglement
of the multipartite (multi-qubits) to be used in quantum information
\\ ( http://arxiv.org/abs/0909.3433 , 543kb)
Date: Fri, 18 Sep 2009 13:53:02 GMT (30kb)

Title: Optimized Dynamical Decoupling for Power Law Noise Spectra
Authors: S. Pasini and G.S. Uhrig
Categories: quant-ph
Comments: 9 pages, 5 figures
   We analyze the suppression of decoherence by means of dynamical decoupling in
the pure-dephasing spin-boson model for baths with power law spectra. The
sequence of ideal $\pi$ pulses is optimized according to the power of the bath.
We expand the decoherence function and separate the cancelling divergences from
the relevant terms. The proposed sequence is chosen to be the one minimizing
the decoherence function. By construction, it provides the best performance. We
analytically derive the conditions that must be satisfied. The resulting
equations are solved numerically. The solutions are very close to the
Carr-Purcell-Meiboom-Gill (CPMG) sequence for a soft cutoff of the bath while
they approach the Uhrig dynamical-decoupling (UDD) sequence as the cutoff
becomes harder.
\\ ( http://arxiv.org/abs/0909.3439 , 30kb)
Date: Fri, 18 Sep 2009 22:37:58 GMT (737kb,D)

Title: Pure Mott phases in confined ultra-cold atomic systems
Authors: V.G. Rousseau, G.G. Batrouni, D.E. Sheehy, J. Moreno, and M. Jarrell
Categories: cond-mat.quant-gas
Comments: 4 Pages, 6 figures
   We propose a novel scheme for confining atoms to optical lattices by
engineering a spatially-inhomogeneous hopping matrix element in the
Hubbard-model (HM) description, a situation we term off-diagonal confinement
(ODC). We show, via an exact numerical solution of the boson HM with ODC, that
this scheme possesses distinct advantages over the conventional method of
confining atoms using an additional trapping potential, including the presence
of incompressible Mott phases at commensurate filling and a phase diagram that
is similar to the uniform HM. The experimental implementation of ODC will thus
allow a more faithful realization of correlated phases of interest in cold atom
\\ ( http://arxiv.org/abs/0909.3543 , 737kb)
Date: Mon, 21 Sep 2009 11:08:56 GMT (429kb)

Title: Study of Kosterlitz-Thouless transition of Bose systems governed by a
   random potential using quantum Monte Carlo simulations
Authors: Hiroki Kuroyanagi, Mitsuaki Tsukamoto and Makoto Tsubota
Categories: cond-mat.stat-mech
Comments: 6 pages, 11 figures
   We study the effects of a random potential on Kosterlitz-Thouless (KT)
transitions in two-dimensional Bose systems by means of quantum Monte Carlo
simulation. We use the Bose-Hubbard model imposed on the hard-core limit. The
potential differs among different sites, whose distribution is assumed to obey
a Gaussian distribution. Calculating the superfluid density, the specific heat
and the correlation functions leads to a superfluid-disordered phase diagram.
As the potential becomes more random, the KT transition temperature reduces,
but the superfluid phase survives for broad values of the randomness. Our work
is related to recent experiments as $^4$He in porous materials and disordered
cold atomic gases.
\\ ( http://arxiv.org/abs/0909.3563 , 429kb)
Date: Mon, 21 Sep 2009 06:09:15 GMT (49kb)

Title: Density matrix renormalization group for bosonic quantum Hall effect
Authors: D. L. Kovrizhin
Categories: cond-mat.str-el cond-mat.quant-gas
Comments: 8 pages, 7 figures
   We developed a new Density Matrix Renormalization Group technique to study
quantum Hall fractions of fast rotating bosons. In this paper we present a
discussion of the method together with the results which we obtain in three
distinct cases of the narrow channel, cylinder and spherical geometries. In the
narrow channel case, which is relevant to anisotropic confining traps in the
limit of extremely fast rotation, we find a series of zero-temperature phase
transitions in the strongly interacting regime as a function of the interaction
strength between bosons. We compute energies and density profiles for different
filling fractions on a cylinder and compare the convergence rates of the method
in the cylinder and a sphere geometries.
\\ ( http://arxiv.org/abs/0909.3693 , 49kb)
Date: Mon, 21 Sep 2009 13:09:45 GMT (163kb)

Title: Hierarchical theory of quantum dissipation: Partial fraction
   decomposition scheme
Authors: Jian Xu, Rui-Xue Xu, Meng Luo, and YiJing Yan
Categories: cond-mat.stat-mech
Comments: 8 pages, 3 figures
   We propose a partial fraction decomposition scheme to the construction of
hierarchical equations of motion theory for bosonic quantum dissipation
systems. The expansion of Bose--Einstein function in this scheme shows similar
properties as it applies for Fermi function. The performance of the resulting
quantum dissipation theory is exemplified with spin--boson systems. In all
cases we have tested the new theory performs much better, about an order of
magnitude faster, than the best available conventional theory based on
Matsubara spectral decomposition scheme.
\\ ( http://arxiv.org/abs/0909.3762 , 163kb)
Date: Mon, 21 Sep 2009 14:01:50 GMT (196kb)

Title: Statistics of a Free Single Quantum Particle at a Finite Temperature
Authors: Jian-Ping Peng
Categories: cond-mat.stat-mech
Comments: 9 pages, 2figures
   We present a model to study the statistics of a single structureless quantum
particle freely moving in a space at a finite temperature. It is shown that the
quantum particle feels the temperature and can exchange energy with its
environment in the form of heat transfer. The underlying mechanism is
diffraction at the edge of the wave front of its matter wave. Within the
framework of modern quantum and statistical mechanics, analytical expressions
are obtained for an exact description of the whole irreversible process.
\\ ( http://arxiv.org/abs/0909.3775 , 196kb)
Date: Mon, 21 Sep 2009 15:13:33 GMT (9kb)

Title: Motion of a Vortex Filament in Superfluid 4He: Effects of Friction Force
   in the Hall-Vinen Phenomenological Model
Authors: Bhimsen K. Shivamoggi
Categories: cond-mat.other
   Motion of a vortex filament in superfluid 4He is considered by using the
Hall-Vinen phenomenological model for the scattering process between the vortex
and thermal excitations in liquid 4He. Hall-Vinen equations are formulated
first in the intrinsic geometric parameter space to obtain insights (like the
fundamental importance of one aspect of the friction term, associated with the
friction coefficient alpha, in the Hall-Vinen notation, as well as a proper
rationale for the previous neglect of the other aspect of the friction term,
associated with the friction coefficient alpha^prime) into the underlying
physical features as well as highlight difficulties in making further progress
on this route. A reformulation of the Hall-Vinen equation in the extrinsic
vortex filament coordinate space is then shown to provide a useful alternative
approach in this regard. Though the friction term associated with alpha, for
very small alpha, has little capacity to make significant contribution to the
vortex motion in a quantitative way it appears to be able to change the vortex
motion aspects in a quantitative way.
\\ ( http://arxiv.org/abs/0909.3799 , 9kb)
Date: Mon, 21 Sep 2009 17:13:21 GMT (1757kb,D)

Title: Delocalization to self-trapping transition of a Bose fluid confined in a
   double well potential. An analysis via one- and two-body correlation
Authors: S. F. Caballero Benitez, V. Romero-Rochin, and R. Paredes
Categories: cond-mat.quant-gas cond-mat.stat-mech
Comments: 16 pages, 9 figures
   We revisit the coherent or delocalized to self-trapping transition in an
interacting bosonic quantum fluid confined in a double well potential, in the
context of full quantum calculations. We show that an $N$-particle Bose-Hubbard
fluid reaches an stationary state through the two-body interactions. These
stationary states are either delocalized or self-trapped in one of the wells,
the former appearing as coherent oscillations in the mean-field approximation.
By studying one- and two-body properties in the energy eigenstates and in a set
of coherent states, we show that the delocalized to self-trapped transition
occurs as a function of the energy of the fluid, provided the interparticle
interaction is above a critical or threshold value. We argue that this is a
type of symmetry-breaking continuous phase transition.
\\ ( http://arxiv.org/abs/0909.3819 , 1757kb)
Date: Mon, 21 Sep 2009 17:55:30 GMT (197kb)

Title: Clock shifts of optical transitions in ultracold atomic gases
Authors: Zhenhua Yu, C.J. Pethick
Categories: cond-mat.quant-gas
Comments: 4 pages, 1 figure, NORDITA-2009-58
   We calculate the shift, due to interatomic interactions, of an optical
transition in an atomic Fermi gas trapped in an optical lattice, as in recent
experiments of Campbell {\it et al.}, Science {\bf 324}, 360 (2009). Using a
pseudospin formalism to describe the density matrix of the internal two states
of the optical transition, we derive a Bloch equation which incorporates both
the spatial inhomogeneity of the probe laser field and the interatomic
interactions. Expressions are given for the frequency shift as a function of
the pulse duration, detuning of the probe laser, and the spatial dependence of
the electric field of the probe beam. In the low temperature semiclassical
regime, we find that the magnitude of the shift is proportional to the
\\ ( http://arxiv.org/abs/0909.3825 , 197kb)
Date: Sun, 20 Sep 2009 17:14:41 GMT (699kb)

Title: Hyperfine structure in the microwave spectra of ultracold polar
Authors: Hong Ran, J. Aldegunde, Jeremy M. Hutson
Categories: physics.chem-ph quant-ph
   We investigate the microwave spectra of ultracold alkali metal dimers in
magnetic, electric and combined fields, taking account of the hyperfine
structure due to the nuclear spins. We consider the molecules 41K87Rb and
7Li133Cs, which are the targets of current experiments and demonstrate two
extremes of large and small nuclear quadrupole coupling. We calculate the
frequencies and intensities of transitions that may be used to transfer
ultracold molecules between hyperfine states in a magnetic field, employing
different polarizations of microwave radiation. In an electric field, the
hyperfine levels display narrow avoided crossings at specific fields that we
explain in terms of molecular alignment. The hyperfine splittings that arise in
electric fields may hinder individual addressing in schemes to use ultracold
molecules in quantum computation, but the structure of the spectra is
suppressed in combined fields.
\\ ( http://arxiv.org/abs/0909.3644 , 699kb)
Date: Mon, 21 Sep 2009 20:01:03 GMT (393kb)

Title: Coreless vorticity in multicomponent Bose and Fermi superfluids
Authors: G. Catelani, E. A. Yuzbashyan
Categories: cond-mat.quant-gas
Comments: 7 pages, 4 figures
   We consider quantized vortices in two-component Bose-Einstein condensates and
three-component Fermi gases with attractive interactions. In these systems, the
vortex core can be either empty (normal in the fermion case) or filled with
another superfluid. We determine critical values of the parameters -- chemical
potentials, scattering lengths and, for Fermi gases, temperature -- at which a
phase transition between the two types of vortices occurs. Population imbalance
can lead to superfluid core (coreless) vorticity in multicomponent superfluids
which otherwise support only usual vortices. For multicomponent Fermi gases, we
construct the phase diagram including regions of coreless vorticity. We extend
our results to trapped bosons and fermions using an appropriate local
approximation, which goes beyond the usual Thomas-Fermi approximation for
trapped bosons.
\\ ( http://arxiv.org/abs/0909.3851 , 393kb)
Date: Tue, 22 Sep 2009 06:53:35 GMT (10kb)

Title: Gross-Pitaevskii Equation for a System of Randomly Interacting Cold
Authors: J. van Baardewijk
Categories: cond-mat.dis-nn cond-mat.stat-mech
Comments: 6 pages
   Random interaction models have been successful in describing the amorphous
properties of solids such as spin-glasses and structural glasses. This
modelling approach is applied to a system of zero-spin cold bosons moving in an
amorphous environment. The bosons are given to interact according to a
non-random hard-core interaction. Additionally the bosons are subjected to a
random interaction potential similar to that used for glasses. The approach is
to apply a combination of replica methods and field theoretic techniques
developed for superfluid Bose systems. This leads to an equation for the
low-temperature Bose-Einstein condensate which is derived in the Hartree-Fock
approximation. The equation is similar to the Gross-Pitaevskii equation, but
the hard-core coupling constant is renormalised by the presence of the random
interactions in a position dependent way. The amorphous contribution contains
the replica diagonal and off-diagonal Green's functions, for which the Dyson
equations are formulated.
\\ ( http://arxiv.org/abs/0909.3920 , 10kb)
Date: Tue, 22 Sep 2009 10:09:28 GMT (100kb)

Title: Gauge-Away Effect in Cold Gases on Optical Lattices
Authors: O. Boada, A. Celi and J.I. Latorre
Categories: cond-mat.quant-gas cond-mat.other
Comments: 4 pages, 2 figures, revtex style
   It is shown that a simple modification of the geometry in which Raman lasers
are applied to a cold gas in an optical lattice results in transforming the
emerging effective electromagnetic field into a pure gauge. This contrived
gauge-away effect can be observed experimentally by measuring the
Mott-Insulator to Superfluid critical point. The underlying mechanism for this
phenomenon is the ability to engineer the transfer of the transverse component
of the gauge potential into its longitudinal one.
\\ ( http://arxiv.org/abs/0909.3937 , 100kb)
Date: Tue, 22 Sep 2009 13:49:25 GMT (346kb)

Title: Supersymmetric Response of Bose-Fermi Mixture to Photoassociation
Authors: T. Shi, Yue Yu, and C. P. Sun
Categories: cond-mat.other
Comments: 5 pages, 3 figures
   We study supersymmetric (SUSY) responses to a photoassociation process in a
mixture of Bose molecules $b$ and Fermi atoms $f$ which turn to mutual
superpartners for a set of proper parameters. We consider the molecule $b$ to
be a bound state of the atom $f$ and another Fermi atom $F$ with different
species. The $b$-$f$ mixture and a free $F$ atom gas are loaded in an optical
lattice. The SUSY nature of the mixture can be signaled in the response to a
photon induced atom-molecule transition: While two new types of fermionic
excitations, an individual $b$ particle-$f$ hole pair continuum and the
Goldstino-like collective mode, are concomitant for a generic $b$-$f$ mixture,
the former is completely suppressed in the SUSY $b$-$f$ mixture and the
zero-momentum mode of the latter approaches to an exact eigenstate. This SUSY
response can be detected by means of the spectroscopy method, e.g., the
photoassociation spectrum which displays the molecular formation rate of $%
Ff\to b$.
\\ ( http://arxiv.org/abs/0909.3996 , 346kb)
Date: Tue, 22 Sep 2009 18:01:37 GMT (258kb,D)

Title: Weakly Bound Cluster States of Efimov Character
Authors: Javier von Stecher
Categories: cond-mat.quant-gas
Comments: 4+ pages, 3 figures
   We study the behavior of weakly bound clusters and their relation to the
well-known three-body Efimov states. We propose a model Hamiltonian that allows
the independent control of two- and three-body physics. To test the validity of
the model potential, we reproduce predictions of three- and four-body universal
states. Then we extend our study to larger cluster systems by combining
numerical techniques such as correlated-Gaussian and diffusion Monte Carlo
methods. We identify a series of universal cluster states that can be
qualitatively interpreted as adding one particle at a time to an Efimov trimer.
Experimental signatures of these cluster states are discussed.
\\ ( http://arxiv.org/abs/0909.4056 , 258kb)
Date: Tue, 22 Sep 2009 11:06:31 GMT (213kb)

Title: Geomeric phases in Quantum Mechanics
Authors: Y.Ben-Aryeh
Categories: quant-ph
Comments: 31 pages
   Various phenomena related to geometric phases in quantum mechanics are
reviewed and explained by analyzing some examples.The concepts of 'parallelism'
,'connections' and 'curvatures' are applied to Aharonov-Bohm (AB) effect, to
U(1)phase rotation, to SU(2) phase rotation and to holonomic quantum
computation (HQC). The connections in Schrodinger equations are treated by two
alternative approaches. Implementation of HQC is demonstrated by the use of
'dark states' including detailed calculations with the connections, for
implementing the quantum gates. 'Anyons' are related to the symmetries of the
wave functions,in a two-dimensional space, and the use of this concept is
demonstrated by analyzing an example taken from the field of Quantum Hall
\\ ( http://arxiv.org/abs/0909.3958 , 213kb)
Date: Tue, 22 Sep 2009 20:59:52 GMT (2369kb)

Title: Vortex Synchronization in Bose-Einstein Condensates: A Time-Dependent
   Gross-Pitaevskii Equation Approach
Authors: Ryan Barnett, Edward Chen, and Gil Refael
Categories: cond-mat.quant-gas
Comments: 6.1 pages, 3 figures
   In this work we consider vortex lattices in rotating Bose-Einstein
Condensates composed of two species of bosons having different masses.
Previously [1] it was claimed that the vortices of the two species form bound
pairs and the two vortex lattices lock. Remarkably, the two condensates and the
external drive all rotate at different speeds due to the disparity of the
masses of the constituent bosons. In this paper we study the system by solving
the full two-component Gross-Pitaevskii equations numerically. Using this
approach we verify the stability of the putative locked state which is found to
exist within a disk centered on the axis of rotation and which depends on the
mass ratio of the two bosons. We also show that an analytic estimate of this
locking radius based on a two-body force calculation agrees well with the
numerical results.
\\ ( http://arxiv.org/abs/0909.4072 , 2369kb)
Date: Tue, 22 Sep 2009 21:08:04 GMT (162kb)

Title: Superfluid-insulator transition of disordered bosons in one-dimension
Authors: Ehud Altman, Yariv Kafri, Anatoli Polkovnikov, Gil Refael
Categories: cond-mat.dis-nn cond-mat.supr-con
Comments: 16 pages
   We study the superfluid-insulator transition in a one dimensional system of
interacting bosons, modeled as a disordered Josephson array, using a strong
randomness real space renormalization group technique. Unlike perturbative
methods, this approach does not suffer from run-away flows and allows us to
study the complete phase diagram. We show that the superfluid insulator
transition is always Kosterlitz- Thouless like in the way that length and time
scales diverge at the critical point. Interestingly however, we find that the
transition at strong disorder occurs at a non universal value of the Luttinger
parameter, which depends on the disorder strength. This result places the
transition in a universality class different from the weak disorder transition
first analyzed by Giamarchi and Schulz [Europhys. Lett. {\bf 3}, 1287 (1987)].
While the details of the disorder potential are unimportant at the critical
point, the type of disorder does influence the properties of the insulating
phases. We find three classes of insulators which arise for different classes
of disorder potential. For disorder only in the charging energies and Josephson
coupling constants, at integer filling we find an incompressible but gapless
Mott glass phase. If both integer and half integer filling factors are allowed
then the corresponding phase is a random singlet insulator, which has a
divergent compressibility. Finally in a generic disorder potential the
insulator is a Bose glass with a finite compressibility.
\\ ( http://arxiv.org/abs/0909.4096 , 162kb)
Date: Wed, 23 Sep 2009 10:13:28 GMT (11kb)

Title: Delayed response of a fermion-pair condensate to a modulation of the
   interaction strength
Authors: J. Plata
Categories: cond-mat.quant-gas
Comments: 6 pages
Journal-ref: Europhysics Letters 87 (2009) 50001
   The effect of a sinusoidal modulation of the interaction strength on a
fermion-pair condensate is analytically studied. The system is described by a
generalization of the coupled fermion-boson model that incorporates a
time-dependent intermode coupling induced via a magnetic Feshbach resonance.
Nontrivial effects are shown to emerge depending on the relative magnitude of
the modulation period and the relaxation time of the condensate. Specifically,
a nonadiabatic modulation drives the system out of thermal equilibrium: the
external field induces a variation of the quasiparticle energies, and, in turn,
a disequilibrium of the associated populations. The subsequent relaxation
process is studied and an analytical description of the gap dynamics is
obtained. Recent experimental findings are explained: the delay observed in the
response to the applied field is understood as a temperature effect linked to
the condensate relaxation time.
\\ ( http://arxiv.org/abs/0909.4168 , 11kb)
Date: Wed, 23 Sep 2009 14:32:27 GMT (333kb)

Title: Effective magnetic fields for stationary light
Authors: J. Otterbach, J. Ruseckas, R. G. Unanyan, G. Juzeliunas, M.
Categories: quant-ph
   We describe a method to create effective gauge potentials for
stationary-light polaritons in two or three spatial dimensions. When stationary
light is created in the interaction with a uniformly rotating ensemble of
coherently driven double $\Lambda$ atoms, the equation of motion is that of a
massive Schr\"odinger particle in an effective magnetic field. In addition a
repulsive scalar potential emerges which can however be compensated by a
space-dependent detuning. Since the effective interaction area for the
polaritons can be made large, degenerate Landau levels can be created with
degeneracy well above 100. This opens the possibility to study the bosonic
analogue of the fractional quantum Hall effect for interacting stationary-light
\\ ( http://arxiv.org/abs/0909.4219 , 333kb)
Date: Thu, 24 Sep 2009 10:34:19 GMT (598kb)

Title: Two-channel model of photoassociation in the vicinity of a Feshbach
Authors: Philipp-Immanuel Schneider and Alejandro Saenz
Categories: cond-mat.quant-gas
Comments: 4 pages, 2 figures
   We derive the two-channel (TC) description of the photoassociation (PA)
process in the presence of a magnetic Feshbach resonance and compare to full
coupled multi-channel calculations for the scattering of $^{6}$Li-$^{87}$Rb.
Previously derived results [P. Pellegrini et al., Phys. Rev. Lett. 101, 053201
(2008)] are corrected. The PA process is shown to be fully described by two
parameters: the maximal transition rate and the point of vanishing transition
rate. The TC approximation reproduces excellently the PA transition rates of
the full multi-channel calculation and reveals, e.g., that the enhancement of
the rate at a resonance is directly connected to the position of vanishing
rate. For the description of two independent resonances it was found that only
three parameters completely characterize the PA process.
\\ ( http://arxiv.org/abs/0909.4406 , 598kb)
Date: Thu, 24 Sep 2009 12:38:40 GMT (2899kb,D)

Title: Phase contrast imaging of Bose condensed clouds
Authors: R. Meppelink, R. A. Rozendaal, S. B. Koller, J. M. Vogels and P. van
   der Straten
Categories: cond-mat.quant-gas
Comments: 12 pages, submitted to Physical Review A
   Phase contrast imaging is used to observe Bose-Einstein condensates (BECs) at
finite temperature in situ. The imaging technique is used to accurately derive
the absolute phase shift of a probe laser beam due to both the condensate and
the thermal cloud. The accuracy of the method is enhanced by using the
periodicity of the intensity signal as a function of the accumulated phase. The
measured density profiles can be described using a two relevant parameter fit,
in which only the chemical potential and the temperature are to be determined.
This allows us to directly compare the measured density profiles to different
mean-field models in which the interaction between the condensed and thermal
atoms is taken into account to various degrees.
\\ ( http://arxiv.org/abs/0909.4429 , 2899kb)
Date: Thu, 24 Sep 2009 11:01:04 GMT (3414kb)

Title: Particles-vortex interactions and flow visualization in He4
Authors: Yuri A. Sergeev and Carlo F. Barenghi
Categories: cond-mat.other
Comments: To appear in the J Low Temperature Physics
   Recent experiments have demonstrated a remarkable progress in implementing
and use of the Particle Image Velocimetry (PIV) and particle tracking
techniques for the study of turbulence in He4. However, an interpretation of
the experimental data in the superfluid phase requires understanding how the
motion of tracer particles is affected by the two components, the viscous
normal fluid and the inviscid superfluid. Of a particular importance is the
problem of particle interactions with quantized vortex lines which may not only
strongly affect the particle motion, but, under certain conditions, may even
trap particles on quantized vortex cores. The article reviews recent
theoretical, numerical, and experimental results in this rapidly developing
area of research, putting critically together recent results, and solving
apparent inconsistencies. Also discussed is a closely related technique of
detection of quantized vortices negative ion bubbles in He4.
\\ ( http://arxiv.org/abs/0909.4451 , 3414kb)
Date: Thu, 24 Sep 2009 16:42:11 GMT (5651kb)

Title: Quantum control and measurement of atomic spins in polarization
Authors: Ivan H. Deutsch, Poul S. Jessen
Categories: quant-ph
   Quantum control and measurement are two sides of the same coin. To affect a
dynamical map, well-designed time-dependent control fields must be applied to
the system of interest. To read out the quantum state, information about the
system must be transferred to a probe field. We study a particular example of
this dual action in the context of quantum control and measurement of atomic
spins through the light-shift interaction with an off-resonant optical probe.
By introducing an irreducible tensor decomposition, we identify the coupling of
the Stokes vector of the light field with moments of the atomic spin state.
This shows how polarization spectroscopy can be used for continuous weak
measurement of atomic observables that evolve as a function of time.
Simultaneously, the state-dependent light shift induced by the probe field can
drive nonlinear dynamics of the spin, and can be used to generate arbitrary
unitary transformations on the atoms. We revisit the derivation of the master
equation in order to give a unified description of spin dynamics in the
presence of both nonlinear dynamics and photon scattering. Based on this
formalism, we review applications to quantum control, including the design of
state-to-state mappings, and quantum-state reconstruction via continuous weak
measurement on a dynamically controlled ensemble.
\\ ( http://arxiv.org/abs/0909.4506 , 5651kb)
Date: Thu, 24 Sep 2009 02:01:44 GMT (418kb)

Title: Resonant Coupling in the Heteronuclear Alkali Dimers for Direct
   Photoassociative Formation of X(0,0) Ultracold Molecules
Authors: W.C. Stwalley, J. RayMajumder, M. Bellos, R. Carollo, M. Recore, M.
Categories: physics.atom-ph
Comments: 20 pages, 12 figures, Submitted to Journal of Physical Chemistry A
   Promising pathways for photoassociative formation of ultracold heteronuclear
alkali metal dimers in their lowest rovibronic levels (denoted X(0,0)) are
examined using high quality ab initio calculations of potential energy curves
currently available. A promising pathway for KRb, involving the resonant
coupling of the $2 ^1\Pi$ and $1 ^1\Pi $ states just below the lowest excited
asymptote (K($4s$)+Rb($5p_{1/2}$)), is found to occur also for RbCs and less
promisingly for KCs as well. The resonant coupling of the $3 ^1 \Sigma ^+ $ and
$1 ^1\Pi $ states, also just below the lowest excited asymptote, is found to be
promising for LiNa, LiK, LiRb, and less promising for LiCs and KCs. Direct
photoassociation to the $1 ^1\Pi $ state near dissociation appears promising in
the final dimers, NaK, NaRb, and NaCs, although detuning more than 100
cm$^{-1}$ below the lowest excited asymptote may be required.
\\ ( http://arxiv.org/abs/0909.4347 , 418kb)
Date: Thu, 24 Sep 2009 14:07:37 GMT (1453kb)

Title: Mimicking multi-channel scattering with single-channel approaches
Authors: Sergey Grishkevich, Philipp-Immanuel Schneider, Yulian V. Vanne and
   Alejandro Saenz
Categories: physics.atom-ph physics.atm-clus
Comments: 15 pages, 10 figures
   The collision of two atoms is an intrinsic multi-channel (MC) problem as
becomes especially obvious in the presence of Feshbach resonances. Due to its
complexity, however, single-channel (SC) approximations, which reproduce the
long-range behavior of the open channel, are often applied in calculations. In
this work the complete MC problem is solved numerically for the magnetic
Feshbach resonances (MFRs) in collisions between generic ultracold 6Li and 87Rb
atoms in the ground state and in the presence of a static magnetic field B. The
obtained MC solutions are used to test various existing as well as presently
developed SC approaches. It was found that many aspects even at short
internuclear distances are qualitatively well reflected. This can be used to
investigate molecular processes in the presence of an external trap or in
many-body systems that can be feasibly treated only within the framework of the
SC approximation. The applicability of various SC approximations is tested for
a transition to the absolute vibrational ground state around an MFR. The
conformance of the SC approaches is explained by the two-channel approximation
for the MFR.
\\ ( http://arxiv.org/abs/0909.4448 , 1453kb)

The replacements:

replaced with revised version Fri, 18 Sep 2009 10:05:44 GMT (54kb)

Title: The effects of next to nearest neighbor hopping on Bose-Einstein
   condensation in cubic lattices
Authors: G. K. Chaudhary and R. Ramakumar
Categories: cond-mat.stat-mech cond-mat.other
Comments: revised version, 10 pages with figures, intro and conclusions
   modified, more results added, references added
\\ ( http://arxiv.org/abs/0803.3888 , 54kb)
replaced with revised version Fri, 18 Sep 2009 09:44:45 GMT (167kb)

Title: Bose-Einstein condensate in a quartic potential: Static and Dynamic
Authors: G. K. Chaudhary, Amit K Chattopadhyay, R. Ramakumar
Categories: cond-mat.other cond-mat.stat-mech
Comments: revised version, content reorganized, 15 pages including figures,
   references added
\\ ( http://arxiv.org/abs/0812.0246 , 167kb)
replaced with revised version Thu, 17 Sep 2009 22:51:32 GMT (115kb)

Title: A geometrical approach to the dynamics of spinor condensates I:
Authors: Ryan Barnett, Daniel Podolsky, Gil Refael
Categories: cond-mat.other cond-mat.str-el
Comments: 12 pages. First paper in two-part series
Journal-ref: Phys. Rev. B 80, 024420 (2009)
\\ ( http://arxiv.org/abs/0812.3403 , 115kb)
replaced with revised version Thu, 17 Sep 2009 22:53:52 GMT (93kb)

Title: A geometrical approach to the dynamics of spinor condensates II:
   Collective modes
Authors: Ryan Barnett, Daniel Podolsky, Gil Refael
Categories: cond-mat.other cond-mat.str-el
Comments: 13 Pages. Sequel to arXiv:0812.3403
Journal-ref: Phys. Rev. B 80, 024420 (2009)
\\ ( http://arxiv.org/abs/0903.1863 , 93kb)
replaced with revised version Fri, 18 Sep 2009 10:25:35 GMT (356kb)

Title: Anderson localization of a weakly interacting one dimensional Bose gas
Authors: T. Paul, M. Albert, P. Schlagheck, P. Leboeuf, N. Pavloff
Categories: cond-mat.quant-gas nlin.PS
Comments: 20 pages, 13 figures
Journal-ref: Phys. Rev. A 80, 033615 (2009)
DOI: 10.1103/PhysRevA.80.033615
\\ ( http://arxiv.org/abs/0907.0098 , 356kb)
replaced with revised version Fri, 18 Sep 2009 08:50:01 GMT (658kb)

Title: Controlled deflection of cold atomic clouds and of Bose-Einstein
Authors: Naceur Gaaloul (PPM, LSAMA), Laurence Pruvost (LAC), Mourad Telmini
   (LSAMA), Eric Charron (PPM)
Categories: quant-ph
Journal-ref: European Physical Journal D 53, 3 (2009) 343
DOI: 10.1140/epjd/e2009-00130-9
\\ ( http://arxiv.org/abs/0709.2636 , 658kb)
replaced with revised version Mon, 21 Sep 2009 02:09:58 GMT (104kb)

Title: Imbalanced superfluid state in an annular disk
Authors: Fei Ye, Yan Chen, Z. D. Wang and F. C. Zhang
Categories: cond-mat.supr-con cond-mat.quant-gas
Comments: 8 pages, 10 figures. Final version with references added and
   discussion on Sarma state removed
Journal-ref: J. Phys.: Condens. Matter 21 (2009) 355701
\\ ( http://arxiv.org/abs/0807.4990 , 104kb)
replaced with revised version Mon, 21 Sep 2009 16:50:22 GMT (18kb)

Title: Correlation dynamics of strongly-correlated bosons in time-dependent
   optical lattices
Authors: Karen Rodriguez, Arturo Arg\"uelles and Luis Santos
Categories: cond-mat.quant-gas cond-mat.other
Comments: 4 pages, 4 figures
\\ ( http://arxiv.org/abs/0905.3312 , 18kb)
replaced with revised version Sun, 20 Sep 2009 07:55:37 GMT (65kb)

Title: Feynman path-integral treatment of the BEC-impurity polaron
Authors: J. Tempere, W. Casteels, M.K. Oberthaler, E. Timmermans, J.T. Devreese
Categories: cond-mat.quant-gas
Comments: 13 pages, 3 figures
\\ ( http://arxiv.org/abs/0906.4455 , 65kb)
replaced with revised version Tue, 22 Sep 2009 06:22:09 GMT (214kb)

Title: 7616: Critical number of ideal Bose gas confined in a cubic box
Authors: Jeong-Hyuck Park and Sang-Woo Kim
Categories: cond-mat.stat-mech cond-mat.other
Comments: 1+20 pages; 3 figures (2 color and 1 B/W), title changed, major
\\ ( http://arxiv.org/abs/0809.4652 , 214kb)
replaced with revised version Tue, 22 Sep 2009 06:47:24 GMT (81kb)

Title: Effect of realistic interatomic interactions and two-body correlation on
   the heat capacity of a trapped BEC
Authors: Anindya Biswas
Categories: cond-mat.quant-gas
Comments: 15 pages, 5 figures
\\ ( http://arxiv.org/abs/0906.5426 , 81kb)
replaced with revised version Tue, 22 Sep 2009 17:34:09 GMT (2065kb)

Title: Vortex structures in rotating Bose-Einstein condensates
Authors: S. I. Matveenko, D. Kovrizhin, S. Ouvry, G. V. Shlyapnikov
Categories: cond-mat.quant-gas cond-mat.stat-mech
Comments: 17 pages, 12 figures, with additions
\\ ( http://arxiv.org/abs/0908.2172 , 2065kb)
replaced with revised version Tue, 22 Sep 2009 14:22:30 GMT (171kb,D)

Title: Quantum jumps and spin dynamics of interacting atoms in a strongly
   coupled atom-cavity system
Authors: M. Khudaverdyan, W. Alt, T. Kampschulte, S. Reick, A. Thobe, A. Widera
   and D. Meschede
Categories: quant-ph
Comments: 4 pages, 4 figures, published version
Journal-ref: Phys. Rev. Lett. 103, 123006 (2009)
DOI: 10.1103/PhysRevLett.103.123006
\\ ( http://arxiv.org/abs/0901.3738 , 171kb)
replaced with revised version Wed, 23 Sep 2009 12:35:54 GMT (587kb)

Title: Creating p-wave superfluids and topological excitations in optical
Authors: P. Massignan, A. Sanpera, M. Lewenstein
Categories: cond-mat.quant-gas
Comments: 4 pages, 4 figures; substantial changes in both text and figures
\\ ( http://arxiv.org/abs/0908.4568 , 587kb)
replaced with revised version Wed, 23 Sep 2009 03:41:37 GMT (346kb)

Title: Supersymmetric Response of Bose-Fermi Mixture to Photoassociation
Authors: T. Shi, Yue Yu, and C. P. Sun
Categories: cond-mat.other
Comments: 5 pages, 3 figures
\\ ( http://arxiv.org/abs/0909.3996 , 346kb)
replaced with revised version Tue, 22 Sep 2009 22:20:03 GMT (271kb)

Title: Space-time sensors using multiple-wave atom levitation
Authors: F. Impens and Ch. J. Bord\'e
Categories: physics.atom-ph cond-mat.other quant-ph
Comments: 5 pages, 4 figures.Final version
Journal-ref: Phys. Rev. A 80, R031602 (2009) (Rapid. Comm.)
\\ ( http://arxiv.org/abs/0808.3380 , 271kb)
replaced with revised version Thu, 24 Sep 2009 14:54:06 GMT (1387kb)

Title: Laser Cooling by Collisional Redistribution of Radiation
Authors: Ulrich Vogl and Martin Weitz
Categories: cond-mat.quant-gas physics.atom-ph
Comments: 4 figures
Journal-ref: Nature 461, 70 (2009)
\\ ( http://arxiv.org/abs/0906.2904 , 1387kb)

Till next time,

Dr M. J. Davis,                      Associate Professor in Physics
School of Mathematics and Physics,   ph  : +61 7 334 69824
The University of Queensland,        fax : +61 7 336 51242
Brisbane, QLD 4072,                  mdavis_at_physics.uq.edu.au
Australia.                           www.physics.uq.edu.au/people/mdavis/
Matt's arXiv selection: weekly summary of cold-atom papers from arXiv.org
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Received on Fri Nov 20 2009 - 18:56:28 EST

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