Matt's arXiv selection: week ending 18 April 2008.

From: Matthew Davis <>
Date: Fri, 02 May 2008 21:06:23 +1000

The following message was sent to the matts_arxiv list by Matthew Davis <>

Hi all,

There are 37 new preprints and 20 replacements in this week's mailing.

Date: Fri, 11 Apr 2008 06:31:04 GMT (10kb)

Title: Phase coherence and fragmentation in weakly interacting bosonic gases
Authors: G. S. Paraoanu
Categories: cond-mat.stat-mech
Comments: 5 pages
Journal-ref: Phys. Rev. A 77, 041605(R) (2008)
   We present a theory of measurement-induced interference for weakly
interacting Bose-Einstein condensed (BEC) gases. The many-body state resulting
from the evolution of an initial fragmented (Fock) state can be approximated as
a continuous superposition of Gross-Pitaevskii (GP) states; the measurement
breaks the initial phase symmetry, producing a distribution pattern
corresponding to only one of the GP solutions. We discuss also analytically
solvable models, such as two-mode on-chip adiabatic recombination and soliton
generation in quasi one-dimensional condensates.
\\ ( , 10kb)
Date: Fri, 11 Apr 2008 08:28:40 GMT (228kb)

Title: Realizing and Detecting the Haldane's Quantum Hall effect with Ultracold
Authors: L. B. Shao, Shi-Liang Zhu, L. Sheng, D. Y. Xing, and Z. D. Wang
Categories: cond-mat.mes-hall
Comments: 5 pages
   We design an ingenious scheme to realize the Haldane's quantum Hall model
without Landau level by using ultracold atoms trapped in an optical lattice.
Three standing-wave laser beams are used to construct a wanted honeycomb
lattice, where different on-site energies in two sublattices required in the
Haldane's model can be implemented through tuning the phase of one of the laser
beams. The staggered magnetic field is generated from the Berry phase
associated with the atom moving in a region with other three standing-wave
laser beams. Moreover, we establish a relation between the Hall conductivity
and the equilibrium atomic density upon turning on a stimulated uniform
magnetic field, which enables us to detect the topological Chern number with
the density profile measurement technique that is typically used in ultracold
atoms experiments.
\\ ( , 228kb)
Date: Fri, 11 Apr 2008 08:35:51 GMT (25kb)

Title: Bose-Einstein Quantum Statistics and the Ground State of Solid 4He
Authors: C. Cazorla, G. E. Astrakharchik, J. Casulleras, and J. Boronat
Categories: cond-mat.other
Comments: 5 pages, 4 figures
   The ground state of solid $^4$He is studied using the diffusion Monte Carlo
method and a new trial wave function able to describe the supersolid. The new
wave function is symmetric under the exchange of particles and reproduces the
experimental equation of state. Results for the one-body density matrix show
the existence of off-diagonal long-range order with a very small condensate
fraction $\sim 10^{-4}$. The superfluid density of the commensurate system is
below our resolution threshold, $\rho_s/\rho < 10^{-5}$. With a 1%
concentration of vacancies the superfluid density is manifestly larger,
$\rho_s/\rho=3.2(1) \cdot 10^{-3}$.
\\ ( , 25kb)
Date: Fri, 11 Apr 2008 09:52:45 GMT (157kb)

Title: Statisticsb of the total number of collisions and the ordering time in a
   freely expanding hard-point gas
Authors: Sanjib Sabhapandit, Ioana Bena, and Satya N. Majumdar
Categories: cond-mat.stat-mech
Comments: 18 pages, 5 figures
   We consider a Jepsen gas of $N$ hard-point particles undergoing free
expansion on a line, starting from random initial positions of the particles
having random initial velocities. The particles undergo binary elastic
collisions upon contact and move freely in-between collisions. After a certain
ordering time $T_{o}$, the system reaches a ``fan'' state where all the
velocities are completely ordered from left to right in an increasing fashion
and there is no further collision. We compute analytically the distributions of
(i) the total number of collisions and (ii) the ordering time $T_{o}$. We show
that several features of these distributions are universal.
\\ ( , 157kb)
Date: Fri, 11 Apr 2008 11:48:43 GMT (29kb)

Title: The Binder Cumulant at the Kosterlitz-Thouless Transition
Authors: Martin Hasenbusch
Categories: cond-mat.stat-mech
Comments: 27 pages, 1 figure
   We study the behaviour of the Binder cumulant on finite square lattices at
the Kosterlitz-Thouless phase transition. We determine the fixed point value of
the Binder cumulant and the coefficient of the leading logarithmic correction.
These calculations are supplemented with Monte Carlo simulations of the
classical XY (plane rotator) model, the Villain model and the dual of the
absolute value solid-on-solid model. Using the single cluster algorithm, we
simulate lattices up to L=4096. For the lattice sizes reached, subleading
corrections are needed to fit the data for the Binder cumulant. We demonstrate
that the combined analysis of the Binder cumulant and the second moment
correlation length over the lattice size allows for an accurate determination
of the Kosterlitz-Thouless transition temperature on relatively small lattices.
We test the new method at the example of the 2-component phi^4 model on the
\\ ( , 29kb)
Date: Fri, 11 Apr 2008 12:17:31 GMT (377kb)

Title: Collisional Properties of a Polarized Fermi Gas with Resonant
Authors: G. M. Bruun, A. Recati, C. J. Pethick, H. Smith and S. Stringari
Categories: cond-mat.stat-mech
Comments: 4 pages, 2 figures. Nordita preprint 2008-14
   Two-component polarized Fermi gases at low temperature represent a new normal
Fermi liquid. We show that measurements of the relaxation of the dipole mode
for relative motion of the two components, which corresponds to the giant
resonance in nuclei, will give valuable information about amplitudes for mutual
scattering of the two components. Using the concepts of Fermi-liquid theory, we
estimate the relaxation time for counterflow of the two components, and show
that for current experimental conditions, the motion of the dipole mode would
be intermediate between the hydrodynamic and collisionless limits.
\\ ( , 377kb)
Date: Fri, 11 Apr 2008 14:36:03 GMT (82kb)

Title: Bose-Einstein Condensation of Gases in the Frame of Quantum
   Electrodynamics: Interconnection of Constituents
Authors: Mark E. Perel'man
Categories: cond-mat.other physics.gen-ph
Comments: 6 pages
   Bose-Einstein condensate of rarified atomic gases is considered as the state
formed by exchange of virtual photons, resonant to the lowest levels of atoms;
such representation corresponds to the Einstein opinion about an
inter-influence of condensable particles. Considered interactions directly lead
to the QED structure of nonlinear potential in the Gross-Pitaevskii equation.
Linear momenta that correspond to the thermal energy of condensable atoms are
connected to near field of particles and therefore leave atoms immovable. The
estimations of these effects do not contradict the observed data; the general
quantum principles predict possibility of stimulating of BEC formation by
resonant irradiation. All this requires the spectroscopic investigation of BEC
on different steps of formation.
\\ ( , 82kb)
Date: Fri, 11 Apr 2008 16:24:05 GMT (62kb)

Title: Phase separated charge density wave phase in two species extended
   Bose-Hubbard model
Authors: Tapan Mishra, B. K. Sahoo, Ramesh V. Pai
Categories: cond-mat.stat-mech cond-mat.other
   We study the quantum phase transitions in a two component bose-mixture in a
one-dimensional optical lattice. The calculations have been performed in the
framework of the extended Bose-Hubbard model using the finite size density
matrix renormalization group method. We obtain different phase transitions for
the system for integer filling. When the inter-species on-site and the nearest
neighbor interactions are larger than the intra-species on-site and also the
nearest neighbor interactions, the system exhibits a phase separated charge
density wave (PSCDW) order that is characterized by the two species being
spatially separated and existing in the density wave phases.
\\ ( , 62kb)
Date: Fri, 11 Apr 2008 12:52:44 GMT (31kb)

Title: Quantum circuits for strongly correlated quantum systems
Authors: Frank Verstraete, J. Ignacio Cirac, Jose I. Latorre
Categories: quant-ph
   In recent years, we have witnessed an explosion of experimental tools by
which quantum systems can be manipulated in a controlled and coherent way. One
of the most important goals now is to build quantum simulators, which would
open up the possibility of exciting experiments probing various theories in
regimes that are not achievable under normal lab circumstances. Here we present
a novel approach to gain detailed control on the quantum simulation of strongly
correlated quantum many-body systems by constructing the explicit quantum
circuits that diagonalize their dynamics. We show that the exact quantum
circuits underlying some of the most relevant many-body Hamiltonians only need
a finite amount of local gates. As a particularly simple instance, the full
dynamics of a one-dimensional Quantum Ising model in a transverse field with
four spins is shown to be reproduced using a quantum circuit of only six local
gates. This opens up the possibility of experimentally producing strongly
correlated states, their time evolution at zero time and even thermal
superpositions at zero temperature. Our method also allows to uncover the exact
circuits corresponding to models that exhibit topological order and to
stabilizer states.
\\ ( , 31kb)
Date: Fri, 11 Apr 2008 17:56:41 GMT (10kb)

Title: Counting statistics of interfering Bose-Einstein condensates
Authors: A. L. Shelankov, J. Rammer
Categories: quant-ph
Comments: 7 pages, LaTeX
   A method able to deal with snapshot experimental data, such as the
instantaneous particle distributions in a quantum many-body system, is
presented. Subjecting the many-body wave function to a phase transformation
allows introducing as variables the discrete number of particles detected at
various locations, and the complete statistics of particle distributions is
obtained. To demonstrate the efficiency of the method, we apply it to the
snapshot density statistics of two interfering Bose-Einstein condensates, and
show that it allows a complete discussion of the statistics of interference
fringes in the matter waves.
\\ ( , 10kb)
Date: Sat, 12 Apr 2008 05:33:04 GMT (107kb)

Title: Ground-state properties of interacting two-component Bose gases in a
   one-dimensional harmonic trap
Authors: Yajiang Hao, Shu Chen
Categories: cond-mat.str-el cond-mat.stat-mech
Comments: 6 pages, 5 figures
   We study ground-state properties of interacting two-component boson gases in
a one-dimensional harmonic trap by using the exact numerical diagonalization
method. Based on numerical solutions of many-body Hamiltonians, we calculate
the ground-state density distributions in the whole interaction regime for
different atomic number ratio, intra- and inter-atomic interactions. For the
case with equal intra- and inter-atomic interactions, our results clearly
display the evolution of density distributions from a Bose condensate
distribution to a Fermi-like distribution with the increase of the repulsive
interaction. Particularly, we compare our result in the strong interaction
regime to the exact result in the infinitely repulsive limit which can be
obtained by a generalized Bose-Fermi mapping. We also discuss the general case
with different intra- and inter-atomic interactions and show the rich
configurations of the density profiles.
\\ ( , 107kb)
Date: Mon, 14 Apr 2008 16:51:48 GMT (564kb,D)

Title: Mott-Insulator Transition for Ultracold Fermions in Two-Dimensional
   Optical Lattices
Authors: N. Goldman
Categories: cond-mat.mes-hall
Comments: 7 pages, 7 figures
   In this work we study ultracold Fermions confined in a two-dimensional
optical lattice and we explore the Mott-insulator transition with the
Fermi-Hubbard model. On the basis of a mean-field approach, we study the phase
diagrams in the presence of a harmonic trapping potential. Local Mott-insulator
phases are shown to be generally situated in the center of the trap and
correspond to a vanishing variance of the local density. We then study the
effects induced by rotation on the Mott-insulator phase transition. In
particular, we show that the phase boundary reproduces the edge of the
Hofstadter butterfly.
\\ ( , 564kb)
Date: Sun, 13 Apr 2008 14:36:54 GMT (151kb)

Title: Dynamical self-trapping of Bose-Einstein condensates in shallow optical
Authors: M. Rosenkranz, D. Jaksch, F. Y. Lim, W. Bao
Categories: quant-ph cond-mat.other
Comments: 7 pages, 5 figures, RevTeX4
   We observe a sudden breakdown of the transport of a strongly repulsive
Bose-Einstein condensate through a shallow optical lattice of finite width. By
using accurate numerical methods and an analytical description in terms of
nonlinear Bloch waves, we attribute this behavior to the development of a
self-trapped state. The dependence of this drop on the lattice depth and the
interaction strength is investigated. We show that by applying a constant
offset potential to the lattice region it is possible to prohibit this
self-trapping. We also observe the disappearance of the self-trapped state
after a finite time as a result of the finiteness of the lattice.
\\ ( , 151kb)
Date: Fri, 11 Apr 2008 20:08:04 GMT (640kb)

Title: Limits of the Plane Wave Approximation in the Measurement of Molecular
Authors: Zachary B. Walters, Stefano Tonzani, Chris H. Greene
Categories: physics.atom-ph
   Rescattering electrons offer great potential as probes of molecular
properties on ultrafast timescales. The most famous example is molecular
tomography, in which high harmonic spectra of oriented molecules are mapped to
``tomographic images'' of the relevant molecular orbitals. The accuracy of such
reconstructions may be greatly affected by the distortion of scattering
wavefunctions from their asymptotic forms due to interactions with the parent
ion. We investigate the validity of the commonly used plane wave approximation
in molecular tomography, showing how such distortions affect the resulting
orbital reconstructions.
\\ ( , 640kb)
Date: Sun, 13 Apr 2008 17:12:00 GMT (704kb)

Title: Nonlinear dynamics in an alternating gradient guide for neutral
Authors: M. R. Tarbutt and E. A. Hinds
Categories: physics.atom-ph
Comments: 31 pages, 12 figures
   Neutral particles can be guided and focussed using electric field gradients
that focus in one transverse direction and defocus in the other, alternating
between the two directions. Such a guide is suitable for transporting particles
that are attracted to strong electric fields, which cannot be guided using
static fields. Particles are only transmitted if their initial positions and
transverse speeds lie within the guide's phase space acceptance. Nonlinear
forces are always present in the guide and can severely reduce this acceptance.
We consider the effects of the two most important nonlinear forces, a term in
the force that is cubic in the off-axis displacement, and a nonlinear term
which couples together the two transverse motions. We use approximate
analytical techniques, along with numerical methods, to calculate the influence
of these nonlinear forces on the particle trajectories and on the phase space
acceptance. The cubic term alters the focussing and defocussing powers, leading
either to an increase or a decrease of the acceptance depending on its sign. We
find an approximate analytical result for the phase space acceptance including
this cubic term. Using a perturbation method we show how the coupling term
leads to slow changes in the amplitudes of the transverse oscillations. This
term reduces the acceptance when it reduces the focussing power, but has little
influence when it increases that power. It is not possible to eliminate both
nonlinear terms, but one can be made small at the expense of the other. We show
how to choose the guide parameters so that the acceptance is optimized.
\\ ( , 704kb)
arXiv:0804.1986 (*cross-listing*)
Date: Sat, 12 Apr 2008 04:28:13 GMT (431kb,D)

Title: Evolution from a molecular Rydberg gas to an ultracold plasma in a
   seeded supersonic expansion of NO
Authors: J. P. Morrison, C. J. Rennick, J. S. Keller, and E. R. Grant
Categories: physics.chem-ph physics.atom-ph
Comments: 4 pages (two column) 3 figures
   We report the spontaneous formation of a plasma from a gas of cold Rydberg
molecules. Double-resonant laser excitation promotes nitric oxide, cooled to 1
K in a seeded supersonic molecular beam, to single Rydberg states extending as
deep as 80 cm$^{-1}$ below the lowest ionization threshold. The density of
excited molecules in the illuminated volume is as high as 1 x 10$^{13}$
cm$^{-3}$. This population evolves to produce prompt free electrons and a
durable cold plasma of electrons and intact NO$^{+}$ ions.
\\ ( , 431kb)
Date: Mon, 14 Apr 2008 21:01:05 GMT (10kb)

Title: Non-linear Differential Equations for Correlation Functions of Fermi Gas
   in One Dimension
Authors: E. Bettelheim, A. G. Abanov, and P. Wiegmann
Categories: cond-mat.mes-hall
Comments: 5 pages
   We present new non-linear differential equations for space-time correlation
functions of Fermi gas in one spatial dimension. The correlation functions we
consider describe non-stationary processes out of equilibrium. The equations we
obtain are integrable equations. They generalize known non-linear differential
equations for correlation functions at equilibrium and provide vital tools to
study non-equilibrium dynamics of electronic systems. The method we developed
is based only on Wick's theorem and the hydrodynamic description of the Fermi
gas. Differential equations appear directly in bilinear form.
\\ ( , 10kb)
Date: Tue, 15 Apr 2008 18:23:55 GMT (36kb)

Title: A Mean Field Analysis of Pairing in Asymmetric Fermi Systems at Finite
Authors: Rishi Sharma, Sanjay Reddy
Categories: cond-mat.supr-con cond-mat.stat-mech
Comments: 17 pages, 7 figures
Report-no: LA-UR-08-2124
   We study the phase diagram of a two component Fermi system with a weak
attractive interaction. Our analysis includes the leading order Hartree energy
shifts and pairing correlations at finite temperature and chemical potential
difference between the two fermion species. We show that in an asymmetric
system, the Hartree shift to the single particle energies are important for the
phase competition between normal and superfluid phase and can change the phase
transition curve qualitatively. At large asymmetry we find that a novel but
somewhat fragile superfluid state can be favored due to finite temperature
effects. We also investigate the transition between the normal phase and an
inhomogeneous superfluid phase to study how gradient instabilities evolve with
temperature and asymmetry. Finally, we adopt our analysis to study the density
profiles of similar asymmetric Fermi systems that are being observed in cold
atom experiments.
\\ ( , 36kb)
Date: Tue, 15 Apr 2008 17:04:57 GMT (306kb)

Title: Time evolution of 1D gapless models from a domain-wall initial state:
   SLE continued?
Authors: Pasquale Calabrese, Christian Hagendorf, and Pierre Le Doussal
Categories: cond-mat.stat-mech
Comments: 27 pages, 10 figures
   We study the time evolution of quantum one-dimensional gapless systems
evolving from initial states with a domain-wall. We generalize the
path-integral imaginary time approach that together with boundary conformal
field theory allows to derive the time and space dependence of general
correlation functions. The latter are explicitly obtained for the Ising
universality class, and the typical behavior of one- and two-point functions is
derived for the general case. Possible connections with the stochastic Loewner
evolution are discussed and explicit results for one-point time dependent
averages are obtained for generic \kappa for boundary conditions corresponding
to SLE. We use this set of results to predict the time evolution of the
entanglement entropy and obtain the universal constant shift due to the
presence of a domain wall in the initial state.
\\ ( , 306kb)
Date: Tue, 15 Apr 2008 04:20:29 GMT (549kb)

Title: Optical bistability at low light level due to collective atomic recoil
Authors: M. Vengalattore, M. Hafezi, M. D. Lukin and M. Prentiss
Categories: quant-ph
   We demonstrate optical nonlinearities due to the interaction of weak optical
fields with the collective motion of a strongly dispersive ultracold gas. The
combination of a recoil-induced resonance (RIR) in the high gain regime and
optical waveguiding within the dispersive medium enables us to achieve a
collective atomic cooperativity of $275 \pm 50$ even in the absence of a
cavity. As a result, we observe optical bistability at input powers as low as
20 pW. The present scheme allows for dynamic optical control of the dispersive
properties of the ultracold gas using very weak pulses of light. The
experimental observations are in good agreement with a theoretical model.
\\ ( , 549kb)
Date: Wed, 16 Apr 2008 00:57:00 GMT (282kb)

Title: Applying matrix product operators to model systems with long-range
Authors: Gregory M. Crosswhite, Andrew C. Doherty, Guifre Vidal
Categories: cond-mat.other
Comments: 6 pages, 3 figures
   An algorithm is presented which computes a translationally invariant matrix
product state approximation of the ground state of an infinite 1D system; it
does this by embedding sites into an approximation of the infinite
``environment'' of the chain, allowing the sites to relax, and then merging
them with the environment in order to refine the approximation. By making use
of matrix product operators, our approach is able to directly model any
long-range interaction that can be systematically approximated by a series of
decaying exponentials. We apply our techniques to compute the ground state of
the Haldane-Shastry model and present results.
\\ ( , 282kb)
Date: Wed, 16 Apr 2008 19:02:06 GMT (59kb)

Title: Infinite size density matrix renormalization group, revisited
Authors: I. P. McCulloch
Categories: cond-mat.str-el
Comments: 12 pages, 3 figures
   I revisit the infinite-size variant of the Density Matrix Renormalization
Group (iDMRG) algorithm for obtaining a fixed-point translationally invariant
matrix product wavefunction in the context of one-dimensional quantum systems.
A crucial ingredient of this algorithm is an efficient transformation for
obtaining the matrix elements of the wavefunction as the lattice size is
increased, and I introduce here a versatile transformation that is demonstrated
to be much more effective than previous versions. The resulting algorithm has a
surprisingly close relationship to Vidal's Time Evolving Block Decimation for
infinite systems, but allows much faster convergence. Access to a
translationally invariant matrix product state allows the calculation of
correlation functions based on the transfer matrix, which directly gives the
spectrum of all correlation lengths. I also show some advantages of the Matrix
Product Operator (MPO) technique for constructing expectation values of higher
moments, such as the exact variance $<(H-E)^2>$.
\\ ( , 59kb)
Date: Wed, 16 Apr 2008 12:08:06 GMT (22kb)

Title: Free expansion of a Lieb-Liniger gas: Asymptotic form of the wave
Authors: D. Juki\'c, R. Pezer, T. Gasenzer, H. Buljan
Categories: cond-mat.other
Comments: 7 pages, 2 figures
   The asymptotic form of the wave functions describing a freely expanding
Lieb-Liniger gas is derived by using a Fermi-Bose transformation for
time-dependent states, and the stationary phase approximation. We find that
asymptotically, the wave functions approach the Tonks-Girardeau structure,
while the interaction energy decays as a power law with time,
$E_\mathrm{int}\propto t^{-3}$. The analysis encompasses a large class of
initial conditions, including the ground states of a Lieb-Liniger gas in
physically realistic external potentials.
\\ ( , 22kb)
Date: Wed, 16 Apr 2008 17:22:09 GMT (850kb)

Title: Correlation Effects in Ultracold Two-Dimensional Bose Gases
Authors: Lih-King Lim, C. Morais Smith, and H. T. C. Stoof
Categories: cond-mat.stat-mech
   We study various properties of an ultracold two-dimensional (2D) Bose gas
that are beyond a mean-field description. We first derive the effective
interaction for such a system as realized in current experiments, which
requires the use of an energy dependent $T$-matrix. Using this result, we then
solve the mean-field equation of state of the modified Popov theory, and
compare it with the usual Hartree-Fock theory. We show that even though the
former theory does not suffer from infrared divergences in both the normal and
superfluid phases, there is an unphysical density discontinuity close to the
Berezinskii-Kosterlitz-Thouless transition. We then improve upon the mean-field
description by using a renormalization group approach and show how the density
discontinuity is resolved. The flow equations in 2D, in particular of the
symmetry-broken phase, already contain some unique features pertinent to the 2D
XY model, even though vortices have not been included explicitly. We also
compute various many-body correlators, and show that correlation effects beyond
the Hartree-Fock theory are important already in the normal phase as
criticality is approached. We finally extend our results to the inhomogeneous
case of a trapped Bose gas using the local-density approximation and show that
close to criticality, the renormalization group approach is required for the
accurate determination of the density profile.
\\ ( , 850kb)
Date: Wed, 16 Apr 2008 14:23:50 GMT (876kb)

Title: Anderson localization of a non-interacting Bose-Einstein condensate
Authors: G. Roati, C. D'Errico, L. Fallani, M. Fattori, C. Fort, M. Zaccanti,
   G. Modugno, M. Modugno, M. Inguscio
Categories: cond-mat.dis-nn
Comments: 5 pages
   One of the most intriguing phenomena in physics is the localization of waves
in disordered media. This phenomenon was originally predicted by Anderson,
fifty years ago, in the context of transport of electrons in crystals. Anderson
localization is actually a much more general phenomenon, and it has been
observed in a large variety of systems, including light waves. However, it has
never been observed directly for matter waves. Ultracold atoms open a new
scenario for the study of disorder-induced localization, due to high degree of
control of most of the system parameters, including interaction. Here we employ
for the first time a noninteracting Bose-Einstein condensate to study Anderson
localization. The experiment is performed with a onedimensional quasi-periodic
lattice, a system which features a crossover between extended and exponentially
localized states as in the case of purely random disorder in higher dimensions.
Localization is clearly demonstrated by investigating transport properties,
spatial and momentum distributions. We characterize the crossover, finding that
the critical disorder strength scales with the tunnelling energy of the atoms
in the lattice. Since the interaction in the condensate can be controlled at
will, this system might be employed to solve open questions on the interplay of
disorder and interaction and to explore exotic quantum phases.
\\ ( , 876kb)
Date: Wed, 16 Apr 2008 14:31:51 GMT (57kb)

Title: Phase diagram and binding energy of interacting Bose gases
Authors: M. M\"annel, K. Morawetz, M. Schreiber, P. Lipavsk\'y
Categories: cond-mat.stat-mech
   From the many-body T-matrix the condition for a medium-dependent bound state
and its binding energy is derived for a homogeneous interacting Bose gas. This
condition provides the critical line in the phase diagram in terms of the
medium-dependent scattering length. Separating the Bose pole from the
distribution function the influence of a Bose condensate is discussed and a
thermal minimum of the critical scattering length is found.
\\ ( , 57kb)
Date: Wed, 16 Apr 2008 14:37:00 GMT (115kb)

Title: A Maxwell's demon in the generation of an intense and slow guided beam
Authors: Ga\"el Reinaudi (LKB - Lhomond), David Guery-Odelin (LKB - Lhomond,
Categories: cond-mat.other
Proxy: ccsd hal-00273918
   We analyze quantitatively the generation of a continuous beam of atoms by the
periodic injection of individual packets in a guide, followed by their
overlapping. We show that slowing the packets using a moving mirror before
their overlapping enables an optimal gain on the phase space density of the
generated beam. This is interpreted as a Maxwell's demon type strategy as the
experimentalist exploits the information on the position and velocity of the
center of mass of each packet.
\\ ( , 115kb)
Date: Wed, 16 Apr 2008 16:23:52 GMT (26kb)

Title: Normal state of highly polarized Fermi gases: Full many-body treatment
Authors: R. Combescot and S. Giraud
Categories: cond-mat.soft cond-mat.stat-mech cond-mat.str-el
Comments: 5 pages, 1 figure
   We consider a single \down atom within a Fermi sea of \up atoms. We elucidate
by a full many-body analysis the quite mysterious agreement between Monte-Carlo
results and approximate calculations taking only into account single
particle-hole excitations. It results from a nearly perfect destructive
interference of the contributions of states with more than one particle-hole
pair. This is linked to the remarkable efficiency of the expansion in powers of
hole wavevectors, the lowest order leading to perfect interference. Going up to
two particle-hole pairs gives an essentially perfect agreement with known exact
results. Hence our treatment amounts to an exact solution of this problem.
\\ ( , 26kb)
Date: Wed, 16 Apr 2008 13:13:59 GMT (155kb)

Title: Cold Fermi atomic gases in a pumped optical resonator
Authors: Jonas Larson, Giovanna Morigi, Maciej Lewenstein
Categories: quant-ph
Comments: Two column, three figures
   We study systems of fully polarized ultracold atomic gases obeying Fermi
statistics. The atomic transition interacts dispersively with a mode of a
standing-wave cavity, which is coherently pumped by a laser. In this setup, the
intensity of the intracavity field is determined by the refractive index of the
atomic medium, and thus by the atomic density distribution. Vice-versa, the
density distribution of the atom is determined by the cavity field potential,
whose depth is proportional to the intracavity field amplitude. In this work we
show that this nonlinearity leads to a novel kind of instability in the
intracavity intensity, which differs substantially from dispersive optical
bistability, as this effect is already present in the regime, where the atomic
dipole is proportional to the cavity field. Such instability is driven by the
matter waves fluctuations and exhibits a peculiar dependence on the
fluctuations in the atomic density distribution.
\\ ( , 155kb)
Date: Thu, 17 Apr 2008 00:24:57 GMT (299kb)

Title: Phase Separation in Bose-Fermi-Fermi Mixtures as a Probe of Fermi
Authors: S. G. Bhongale and H. Pu
Categories: cond-mat.stat-mech cond-mat.supr-con
Comments: 4 pages, 3 figures
   We study the phase diagram of a mixture of Bose-Einstein condensate and a
two-component Fermi gas. In particular, we identify the regime where the
homogeneous system becomes unstable again phase separation. We show that, under
proper conditions, the phase separation phenomenon can be exploited as a robust
probe of Fermi superfluid.
\\ ( , 299kb)
Date: Thu, 17 Apr 2008 10:22:58 GMT (222kb)

Title: Ground-state properties of few-Boson system in a one-dimensional hard
   wall potential with split
Authors: Xiangguo Yin, Yajiang Hao, Shu Chen, Yunbo Zhang
Categories: cond-mat.str-el cond-mat.other
Comments: 7 pages, 9 figures
   We carry out a detailed examination of the ground state property of few-boson
system in a one-dimensional hard wall potential with a $\delta -$ split in the
center. In the Tonks-Girardeau limit with infinite repulsion between particles,
we use the Bose-Fermi mapping to construct the exact $N-$ particle ground state
wavefunction which allows us to study the correlation properties accurately.
For the general case with finite inter-particle interaction, the exact
diagonalization method is exploited to study the ground-state density
distribution, occupation number distribution, and momentum distribution for
variable interaction strengths and barrier heights. The secondary peaks in the
momentum distribution reveal the interference between particles on the two
sides of the split, which is more prominent for large barrier strength and
small interaction strength.
\\ ( , 222kb)
Date: Thu, 17 Apr 2008 10:34:50 GMT (43kb)

Title: Fast Convergence of Path Integrals for Many-body Systems
Authors: Aleksandar Bogojevic, Ivana Vidanovic, Antun Balaz, Aleksandar Belic
Categories: cond-mat.stat-mech
Comments: 20 pages, 6 figures, 1 table
Journal-ref: Phys. Lett. A372 (2008) 3341
DOI: 10.1016/j.physleta.2008.01.079
   We generalize a recently developed method for accelerated Monte Carlo
calculation of path integrals to the physically relevant case of generic
many-body systems. This is done by developing an analytic procedure for
constructing a hierarchy of effective actions leading to improvements in
convergence of $N$-fold discretized many-body path integral expressions from
1/N to $1/N^p$ for generic $p$. In this paper we present explicit solutions
within this hierarchy up to level $p=5$. Using this we calculate the low lying
energy levels of a two particle model with quartic interactions for several
values of coupling and demonstrate agreement with analytical results governing
the increase in efficiency of the new method. The applicability of the
developed scheme is further extended to the calculation of energy expectation
values through the construction of associated energy estimators exhibiting the
same speedup in convergence.
\\ ( , 43kb)
Date: Thu, 17 Apr 2008 11:13:34 GMT (116kb)

Title: Probing correlated phases of bosons in optical lattices via trap
Authors: Tommaso Roscilde
Categories: cond-mat.str-el cond-mat.dis-nn
Comments: 4 pages, 4 figures
   We theoretically analyze the response properties of ultracold bosons in
optical lattices to the static variation of the trapping potential. We show
that, upon an increase of such potential (trap squeezing), the density
variations in a central region, with linear size of >~ 10 wavelengths, reflect
that of the bulk system upon changing the chemical potential: hence measuring
the density variations gives direct access to the bulk compressibility. When
combined with standard time-of-flight measurements, this approach has the
potential of unambiguously detecting the appearence of the most fundamental
phases realized by bosons in optical lattices, with or without further external
potentials: superfluid, Mott insulator, band insulator and Bose glass.
\\ ( , 116kb)
Date: Thu, 17 Apr 2008 14:16:10 GMT (92kb)

Title: Perturbation theory for bright spinor Bose--Einstein condensate solitons
Authors: Evgeny V. Doktorov, Jiandong Wang, Jianke Yang
Categories: cond-mat.other
Comments: 12 pages, 3 figures
Journal-ref: Phys. Rev. A 77, 043617 (2008)
   We develop a perturbation theory for bright solitons of the F=1 integrable
spinor Bose-Einstein condensate (BEC) model. The formalism is based on using
the Riemann-Hilbert problem and provides the means to analytically calculate
evolution of the soliton parameters. Both rank-one and rank-two soliton
solutions of the model are obtained. We prove equivalence of the rank-one
soliton and the ferromagnetic rank-two soliton. Taking into account a splitting
of a perturbed polar rank-two soliton into two ferromagnetic solitons, it is
sufficient to elaborate a perturbation theory for the rank-one solitons only.
   Treating a small deviation from the integrability condition as a
perturbation, we describe the spinor BEC soliton dynamics in the adiabatic
approximation. It is shown that the soliton is quite robust against such a
perturbation and preserves its velocity, amplitude, and population of different
spin components, only the soliton frequency acquires a small shift. Results of
numerical simulations agree well with the analytical predictions, demonstrating
only slight soliton profile deformation.
\\ ( , 92kb)
Date: Thu, 17 Apr 2008 19:23:14 GMT (262kb,D)

Title: Soliton response to transient trap variations
Authors: S. Sree Ranjani, Utpal Roy, P. K. Panigrahi and A. K. Kapoor
Categories: cond-mat.other
   The response of bright and dark solitons to rapid variations in an expulsive
longitudinal trap is investigated. We concentrate on the effect of transient
changes in the trap frequency in the form of temporal delta kicks and the
hyperbolic cotangent functions. Exact expressions are obtained for the soliton
profiles. This is accomplished using the fact that a suitable linear
Schrodinger stationary state solution in time can be effectively combined with
the solutions of non-linear Schrodinger equation, for obtaining solutions of
the Gross-Pitaevskii equation with time dependent scattering length in a
harmonic trap. Interestingly, there is rapid pulse amplification in certain
\\ ( , 262kb)
arXiv:0804.1377 (*cross-listing*)
Date: Tue, 8 Apr 2008 22:12:17 GMT (85kb)

Title: Quantum Noise as an Entanglement Meter
Authors: Israel Klich, Leonid Levitov
Categories: quant-ph astro-ph cond-mat.mes-hall hep-th
   Entanglement entropy, which is a measure of quantum correlations between
separate parts of a many-body system, has emerged recently as a fundamental
quantity in broad areas of theoretical physics, from cosmology and field theory
to condensed matter theory and quantum information. The universal appeal of the
entanglement entropy concept is related, in part, to the fact that it is
defined solely in terms of the many-body density matrix of the system, with no
relation to any particular observables. However, for the same reason, it has
not been clear how to access this quantity experimentally. Here we derive a
universal relation between entanglement entropy and the fluctuations of current
flowing through a quantum point contact (QPC) which opens a way to perform a
direct measurement of entanglement entropy. In particular, by utilizing
space-time duality of 1d systems, we relate electric noise generated by opening
and closing the QPC periodically in time with the seminal S = 1/3 log L
prediction of conformal field theory.
\\ ( , 85kb)
Date: Thu, 17 Apr 2008 18:41:46 GMT (163kb)

Title: Analytical solution for optimal squeezing of wave packet of a trapped
   quantum particle
Authors: Ilya Grigorenko
Categories: quant-ph
   Optimal control problem with a goal to squeeze wave packet of a trapped
quantum particle is considered and solved analytically using adiabatic
approximation. The analytical solution that drives the particle into a highly
localized final state is presented for a case of an infinite well trapping
potential. The presented solution may be applied to increase the resolution of
atom lithography.
\\ ( , 163kb)

The replacements:

replaced with revised version Fri, 11 Apr 2008 17:32:04 GMT (598kb)

Title: Bogoliubov theory of quantum correlations in the time-dependent
   Bose-Hubbard model
Authors: Uwe R. Fischer, Ralf Sch\"utzhold, Michael Uhlmann
Categories: cond-mat.other quant-ph
Comments: 11 pages of RevTex4, 2 figures; significantly extended, with several
   analytically solvable cases added, to appear in Physical Review A
\\ ( , 598kb)
replaced with revised version Fri, 11 Apr 2008 14:59:09 GMT (49kb)

Title: Mixtures of strongly interacting bosons in optical lattices
Authors: P. Buonsante, S.M. Giampaolo, F. Illuminati, V. Penna and A. Vezzani
Categories: cond-mat.other quant-ph
Comments: 10 pages, 3 figures; some changes in the text and abstract have been
   introduced; coherence now given in terms of visibility; a couple of new
   reference added
\\ ( , 49kb)
replaced with revised version Mon, 14 Apr 2008 04:57:19 GMT (42kb)

Title: Dynamics of one-dimensional Bose liquids: Andreev-like reflection at
   Y-junctions and absence of the Aharonov-Bohm effect
Authors: Akiyuki Tokuno, Masaki Oshikawa, Eugene Demler
Categories: cond-mat.other cond-mat.mes-hall
Comments: 4 pages, 2 figures, final version
Journal-ref: Phys. Rev. Lett. 100, 140402 (2008)
\\ ( , 42kb)
replaced with revised version Mon, 14 Apr 2008 09:22:07 GMT (12kb)

Title: Microcanonical quantum fluctuation theorems
Authors: Peter Talkner, Peter Hanggi, Manuel Morillo
Categories: cond-mat.stat-mech
Comments: revised and extended version
\\ ( , 12kb)
replaced with revised version Sat, 12 Apr 2008 21:54:04 GMT (85kb)

Title: Emulating Non-Abelian Topological Matter in Cold Atom Optical Lattices
Authors: V. W. Scarola and S. Das Sarma
Categories: cond-mat.other
Journal-ref: Phys. Rev. A 77, 023612 (2008)
\\ ( , 85kb)
replaced with revised version Mon, 14 Apr 2008 12:51:25 GMT (714kb)

Title: Localization and delocalization of ultracold bosonic atoms in finite
   optical lattices
Authors: Dirk-S\"oren L\"uhmann, Kai Bongs, Klaus Sengstock, Daniela Pfannkuche
Categories: cond-mat.other
Comments: 8 pages, 10 figures. Published version
Journal-ref: Phys. Rev. A 77, 023620 (2008)
DOI: 10.1103/PhysRevA.77.023620
\\ ( , 714kb)
replaced with revised version Mon, 14 Apr 2008 09:08:06 GMT (538kb)

Title: Stripe Formation in Fermionic Atoms on 2-D Optical Lattice inside a Box
   Trap: DMRG Studies for Repulsive Hubbard Model with Open Boundary Condition
Authors: M. Machida, M. Okumura, S. Yamada
Categories: cond-mat.str-el
Journal-ref: Phys. Rev. A 77, 033619 (2008)
DOI: 10.1103/PhysRevA.77.033619
\\ ( , 538kb)
replaced with revised version Sun, 13 Apr 2008 07:50:57 GMT (17kb)

Title: Phase Diagram of Cold Polarized Fermi Gas in Two Dimensions
Authors: Lianyi He and Pengfei Zhuang
Categories: cond-mat.supr-con
Comments: V1: 4 pages, 1 figure. V2: 5 pages, 1 figure; typos corrected;
   references added; some statement in the introduction changed; submitted to
\\ ( , 17kb)
replaced with revised version Mon, 14 Apr 2008 08:32:31 GMT (463kb)

Title: Direct observation of Anderson localization of matter-waves in a
   controlled disorder
Authors: Juliette Billy (LCFIO), Vincent Josse (LCFIO), Zhanchun Zuo (LCFIO),
   Alain Bernard (LCFIO), Ben Hambrecht (LCFIO), Pierre Lugan (LCFIO), David
   Cl\'ement (LCFIO), Laurent Sanchez-Palencia (LCFIO), Philippe Bouyer (LCFIO),
   Alain Aspect (LCFIO)
Categories: cond-mat.dis-nn cond-mat.other
Proxy: ccsd hal-00271681
\\ ( , 463kb)
Date: Fri, 11 Apr 2008 22:41:04 GMT (470kb,D)

Title: Scalability of quantum computation with addressable optical lattices
Authors: Travis R. Beals, Jiri Vala, K. Birgitta Whaley
Categories: quant-ph
Comments: 17 pages, 5 figures. Accepted for publication in Physical Review A
   We make a detailed analysis of error mechanisms, gate fidelity, and
scalability of proposals for quantum computation with neutral atoms in
addressable (large lattice constant) optical lattices. We have identified
possible limits to the size of quantum computations, arising in 3D optical
lattices from current limitations on the ability to perform single qubit gates
in parallel and in 2D lattices from constraints on laser power. Our results
suggest that 3D arrays as large as 100 x 100 x 100 sites (i.e., $\sim 10^6$
qubits) may be achievable, provided two-qubit gates can be performed with
sufficiently high precision and degree of parallelizability. Parallelizability
of long range interaction-based two-qubit gates is qualitatively compared to
that of collisional gates. Different methods of performing single qubit gates
are compared, and a lower bound of $1 \times 10^{-5}$ is determined on the
error rate for the error mechanisms affecting $^{133}$Cs in a blue-detuned
lattice with Raman transition-based single qubit gates, given reasonable limits
on experimental parameters.
\\ ( , 470kb)
replaced with revised version Mon, 14 Apr 2008 15:33:59 GMT (978kb,D)

Title: AC electric trapping of neutral atoms
Authors: Sophie Schlunk, Adela Marian, Wieland Schoellkopf, Gerard Meijer
Categories: physics.atom-ph
Comments: 10 pages, 13 figures, updated version, added journal reference
Journal-ref: Phys. Rev. A 77, 043408 (2008)
DOI: 10.1103/PhysRevA.77.043408
\\ ( , 978kb)
replaced with revised version Tue, 15 Apr 2008 18:14:39 GMT (359kb)

Title: Analytic models of ultra-cold atomic collisions at negative energies for
   application to confinement-induced resonances
Authors: S. G. Bhongale, S. J. J. M. F. Kokkelmans, Ivan H. Deutsch
Categories: physics.atom-ph cond-mat.soft quant-ph
Comments: 9 pages
\\ ( , 359kb)
replaced with revised version Wed, 16 Apr 2008 01:32:35 GMT (836kb)

Title: Algorithms for entanglement renormalization
Authors: G. Vidal
Categories: cond-mat.str-el cond-mat.other quant-ph
Comments: 20 pages, 35 figures. Time evolution algorithm removed and
   transferred to arXiv:0706.0868
\\ ( , 836kb)
replaced with revised version Wed, 16 Apr 2008 15:13:31 GMT (481kb)

Title: Optimal transport of ultracold atoms in the non-adiabatic regime
Authors: A. Couvert (LKB - Lhomond), T. Kawalec (LKB - Lhomond), G. Reinaudi
   (LKB - Lhomond), David Guery-Odelin (LKB - Lhomond, LCAR)
Categories: cond-mat.other
Proxy: ccsd hal-00168928
\\ ( , 481kb)
replaced with revised version Wed, 16 Apr 2008 00:05:40 GMT (41kb)

Title: Kinetics of the Phase Separation Transition in Cold-Atom Boson-Fermion
Authors: Dmitry Solenov and Dmitry Mozyrsky
Categories: cond-mat.mes-hall
Comments: 4 pages 1 figure, typos corrected
Journal-ref: Phys. Rev. Lett. 100, 150402 (2008)
\\ ( , 41kb)
replaced with revised version Wed, 16 Apr 2008 08:18:37 GMT (10kb)

Title: Stabilities of one-dimensional stationary states of Bose-Einstein
Authors: Wenhua Hai, Guishu Chong, Jianwen Song
Categories: quant-ph
Comments: 12 pages
Journal-ref: Phys. Lett. A372, 2558 (2008)
\\ ( , 10kb)
replaced with revised version Wed, 16 Apr 2008 14:28:07 GMT (231kb)

Title: Schr\"odinger-cat state creation by a measurement
Authors: I.E. Mazets, G. Kurizki, M.K. Oberthaler, J. Schmiedmayer
Categories: quant-ph
Comments: 4 pages (revtex4), 2 figures
\\ ( , 231kb)
arXiv:0803.1889 (*cross-listing*)
replaced with revised version Wed, 16 Apr 2008 01:17:50 GMT (260kb)

Title: Atom-Pair Tunneling in Optical Lattices
Authors: J.-Q. Liang, J.-L. Liu, W.-D. Li, Z.-J. Li
Categories: cond-mat.other quant-ph
\\ ( , 260kb)
arXiv:0711.4445 (*cross-listing*)
replaced with revised version Thu, 17 Apr 2008 00:45:12 GMT (193kb)

Title: Two-mode Bose-Einstein condensate in a high-frequency driving field that
   directly couples the two modes
Authors: Qi Zhang, Peter Hanggi, and Jiangbin Gong (National Univ. of
Categories: quant-ph cond-mat.stat-mech
Comments: 5 pages, 3 figures, revised version, to appear in Phys. Rev. A
\\ ( , 193kb)
replaced with revised version Thu, 17 Apr 2008 15:30:09 GMT (10kb)

Title: Analytical solution of the bosonic three-body problem
Authors: Alexander O. Gogolin, Christophe Mora, and Reinhold Egger
Categories: cond-mat.other
Comments: 4 pages, published version
Journal-ref: Phys. Rev. Lett. 100, 140404 (2008)
DOI: 10.1103/PhysRevLett.100.140404
\\ ( , 10kb)

Till next time,

Dr M. J. Davis,               Senior Lecturer in Physics
School of Physical Sciences,  email:
University of Queensland,     ph   : +61 7 334 69824
Brisbane, QLD 4072,           fax  : +61 7 336 51242
Matt's arXiv selection: weekly summary of cold-atom papers from
Legal stuff: Unless stated otherwise, this e-mail represents only the
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Received on Thu May 08 2008 - 11:46:30 EST

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