# Matt's arXiv selection: week ending 19 January 2007.

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Fri, 2 Feb 2007 05:24:32 +1000 (EST)

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

Hi all,

The first email bringing you up to date. A massive 40 new preprints:

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Paper: cond-mat/0701270
Date: Fri, 12 Jan 2007 11:27:08 GMT (464kb)

Title: Vortex-antivortex tunneling and the limitations of mean-field theory
Authors: Gentaro Watanabe, C. J. Pethick
Categories: cond-mat.mes-hall
Report-no: NORDITA-2007-3
Subj-class: Mesoscopic Systems and Quantum Hall Effect
\\
We study the quantum dynamics of a model for a vortex in a Bose gas with
repulsive interactions in an anisotropic, harmonic trap previously studied in
mean-field theory by Garc\'ia-Ripoll {\it et al.}, [Phys. Rev. Lett. {\bf 87},
140403 (2001)]. For low excitation energy of the vortex, we show that the
circulation of the vortex undergoes periodic reversals by quantum-mechanical
tunneling, in addition to the oscillations predicted in mean-field theory for
higher excitation energies. With increasing interaction strength or particle
number, vortices become increasingly stable, and the period for reversals by
tunneling increases. Tunneling between vortex and antivortex states is shown to
be described to a good approximation by a Schr\"odinger cat state that is a
superposition of vortex and antivortex states, rather than the mean-field
state, and we derive analytical expression for the oscillation period.
\\ ( http://arXiv.org/abs/cond-mat/0701270 , 464kb)
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Paper: cond-mat/0701272
Date: Fri, 12 Jan 2007 12:57:32 GMT (65kb)

Title: Imbalanced Fermi superfluid in a one-dimensional optical potential
Authors: J. Tempere, M. Wouters, J.T. Devreese
Categories: cond-mat.supr-con
Subj-class: Superconductivity
\\
The superfluid properties of a two-state Fermi mixture in an optical lattice
are profoundly modified when an imbalance in the population of the two states
is present.We present analytical solutions for the free energy, and for the gap
and number equations in the saddle-point approximation describing resonant
superfluidity in the quasi-two-dimensional gas. Inhomogeneities due to the
trapping potentials can be taken into account using the local density
approximation. Analyzing the free energy in this approximation, we find that
phase separation occurs in the layers. The phase diagram of the superfluid and
normal phases is derived and analytical expressions for the phase lines are
presented. We complete the investigation by accounting for effects beyond
mean-field in the BEC limit where the system is more properly described as a
Bose-Fermi mixture of atoms and molecules.
\\ ( http://arXiv.org/abs/cond-mat/0701272 , 65kb)
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Paper: cond-mat/0701277
Date: Fri, 12 Jan 2007 14:52:29 GMT (48kb)

Title: Interferences in the density of two Bose-Einstein condensates consisting
of identical or different atoms
Authors: L. S. Cederbaum, A. I. Streltsov, Y. B. Band, O. E. Alon
Categories: cond-mat.other
Subj-class: Other
\\
The density of two {\it initially independent} condensates which are allowed
to expand and overlap can show interferences as a function of time due to
interparticle interaction. Two situations are separately discussed and
compared: (1) all atoms are identical and (2) each condensate consists of a
different kind of atoms. Illustrative examples are presented.
\\ ( http://arXiv.org/abs/cond-mat/0701277 , 48kb)
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Paper: cond-mat/0701280
Date: Fri, 12 Jan 2007 15:21:48 GMT (35kb)

Title: Phase diagram for interacting Bose gases
Authors: K. Morawetz, M. Maennel and M. Schreiber
Categories: cond-mat.stat-mech cond-mat.other
Subj-class: Statistical Mechanics; Other
\\
We propose a new form of the inversion method in terms of a selfenergy
expansion to access the phase diagram of the Bose-Einstein transition. The
dependence of the critical temperature on the interaction parameter is
calculated. This is discussed with the help of a new condition for
Bose-Einstein condensation in interacting systems which follows from the pole
of the T-matrix in the same way as from the divergence of the medium-dependent
scattering length. A many-body approximation consisting of screened ladder
diagrams is proposed which describes the Monte Carlo data more appropriately.
The specific results are that a non-selfconsistent T-matrix leads to a linear
coefficient in leading order of 4.7, the selfconsistent T-matrix due to the
effective mass to a coefficient of 1.3 and the screened ladder approximation to
2.3 close to the Monte Carlo data.
\\ ( http://arXiv.org/abs/cond-mat/0701280 , 35kb)
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Paper: cond-mat/0701285
Date: Fri, 12 Jan 2007 16:36:15 GMT (427kb)

Title: Stability and dynamics of vortex clusters in nonrotated Bose-Einstein
condensates
Authors: V. Pietila, M. Mottonen, T. Isoshima, J. A. M. Huhtamaki, and S. M. M.
Virtanen
Categories: cond-mat.stat-mech
Subj-class: Statistical Mechanics
Journal-ref: Phys. Rev. A 74, 023603 (2006)
\\
We study stationary clusters of vortices and antivortices in dilute
pancake-shaped Bose-Einstein condensates confined in nonrotating harmonic
traps. Previous theoretical results on the stability properties of these
topologically nontrivial excited states are seemingly contradicting. We clarify
this situation by a systematic stability analysis. The energetic and dynamic
stability of the clusters is determined from the corresponding elementary
excitation spectra obtained by solving the Bogoliubov equations. Furthermore,
we study the temporal evolution of the dynamically unstable clusters. The
stability of the clusters and the characteristics of their destabilizing modes
only depend on the effective strength of the interactions between particles and
the trap anisotropy. For certain values of these parameters, there exist
several dynamical instabilities, but we show that there are also regions in
which some of the clusters are dynamically stable. Moreover, we observe that
the dynamical instability of the clusters does not always imply their
structural instability, and that for some dynamically unstable states
annihilation of the vortices is followed by their regeneration, and revival of
the cluster.
\\ ( http://arXiv.org/abs/cond-mat/0701285 , 427kb)
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Paper: physics/0701150
Date: Fri, 12 Jan 2007 18:26:44 GMT (33kb)

Title: Accurate numerical solutions of the time-dependent Schr\"odinger
equation
Authors: W. van Dijk and F. M. Toyama
Categories: physics.comp-ph
Subj-class: Computational Physics
\\
We present a generalization of the often-used Crank-Nicolson (CN) method of
obtaining numerical solutions of the time-dependent Schr\"odinger equation. The
generalization yields numerical solutions accurate to order $(\Delta x)^{2r-1}$
in space and $(\Delta t)^{2M}$ in time for any positive integers $r$ and $M$,
while CN employ $r=M=1$. We note dramatic improvement in the attainable
precision (circa 10 or greater orders of magnitude) along with several orders
of magnitude reduction of computational time. The improved method is shown to
short-range interactions, wavepacket scattering, and long-time studies of
decaying systems.
\\ ( http://arXiv.org/abs/physics/0701150 , 33kb)
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Paper: cond-mat/0701290
Date: Sat, 13 Jan 2007 01:31:32 GMT (125kb)

Title: Superfluid-Mott-Insulator Transition in a One-Dimensional Optical
Lattice with Double-Well Potentials
Authors: H. C. Jiang, Z. Y. Weng, and T. Xiang
Categories: cond-mat.str-el cond-mat.mes-hall
Subj-class: Strongly Correlated Electrons; Mesoscopic Systems and Quantum Hall
Effect
\\
We study the superfluid-Mott-insulator transition of ultracold bosonic atoms
in a one-dimensional optical lattice with a double-well confining trap using
the density-matrix renormalization group. At low density, the system behaves
similarly as two separated ones inside harmonic traps. At high density,
however, interesting features appear as the consequence of the quantum
tunneling between the two wells and the competition between the "superfluid"
and Mott regions. They are characterized by a rich step-plateau structure in
the visibility and the satellite peaks in the momentum distribution function as
a function of the on-site repulsion. These novel properties shed light on the
understanding of the phase coherence between two coupled condensates and the
off-diagonal correlations between the two wells.
\\ ( http://arXiv.org/abs/cond-mat/0701290 , 125kb)
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Paper: cond-mat/0701321
Date: Mon, 15 Jan 2007 08:41:20 GMT (14kb)

Title: Ultraslow optical waveguiding in an atomic Bose-Einstein condensate
Authors: Devrim Tarhan, Nazmi Postacioglu, Ozgur E. Mustecaplioglu
Categories: cond-mat.other
Comments: 3 pages, 3 figures. submitted to Optics Letters
Subj-class: Other
\\
We investigate waveguiding of ultraslow light pulses in an atomic
Bose-Einstein condensate. We show that under the conditions of off-resonant
electromagnetically induced transparency, waveguiding with a few ultraslow
modes can be realized. The number of modes that can be supported by the
condensate can be controlled by means of experimentally accessible parameters
including trap size, temperature, atomic number density and scattering lengths.
Propagation constants and the mode conditions are determined analytically using
a WKB analysis. Mode profiles are found numerically.
\\ ( http://arXiv.org/abs/cond-mat/0701321 , 14kb)
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Paper: cond-mat/0701325
Date: Mon, 15 Jan 2007 09:27:26 GMT (187kb)

Title: Dispersive effects on optical information storage in Bose-Einstein
condensates with ultra-slow short pulses
Authors: Devrim Tarhan, Alphan Sennaroglu, Ozgur E. Mustecaplioglu
Categories: cond-mat.other
Subj-class: Other
Journal-ref: published in JOSA B, Vol. 23, Issue 9, pp. 1925-1933
\\
We investigate the potential of atomic Bose-Einstein condensates as dynamic
memory devices for coherent optical information processing. Specifically, the
number of ultraslow pulses that can be simultaneously present within the
storage time in the condensate has been analyzed. By modeling short-pulse
propagation through the condensate, taking into account high-order dispersive
properties, constraints on the information storage capacity are discussed. The
roles of temperature, spatial inhomogeneity, the interatomic interactions, and
the coupling laser on the pulse shape are pointed out. For a restricted set of
parameters, it has been found that coherent optical information storage
capacity would be optimized.
\\ ( http://arXiv.org/abs/cond-mat/0701325 , 188kb)
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Paper: cond-mat/0701326
Date: Mon, 15 Jan 2007 10:14:12 GMT (24kb)

Title: Predicted signatures of p-wave superfluid phases and Majorana zero modes
of fermionic atoms in RF absorption
Authors: Eytan Grosfeld, Nigel R. Cooper, Ady Stern, Roni Ilan
Categories: cond-mat.other
Subj-class: Other
\\
We study the superfluid phases of quasi-2D atomic Fermi gases interacting via
a p-wave Feshbach resonance. We calculate the absorption spectra of these
phases under a hyperfine transition, for both non-rotating and rotating
superfluids. We show that one can identify the different phases of the p-wave
superfluid from the absorption spectrum. The absorption spectrum shows clear
signatures of the existence of Majorana zero modes at the cores of vortices of
the weakly-pairing $p_x+ip_y$ phase.
\\ ( http://arXiv.org/abs/cond-mat/0701326 , 24kb)
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Paper: cond-mat/0701328
Date: Mon, 15 Jan 2007 11:18:22 GMT (543kb)

Authors: A. Greiner, J. Sebastian, P. Rehme, A. Aghajani-Talesh, A. Griesmaier,
T.Pfau
Categories: cond-mat.other
Subj-class: Other
\\
We have realized a magnetic guide for ultracold chromium atoms by
guide. We observe an atomic flux of $2 \cdot 10^7$ atoms/s and are able to
control the mean velocity of the guided atoms between 0 m/s and 3 m/s. We
of the guided atoms and discuss the experimental techniques that are used.
\\ ( http://arXiv.org/abs/cond-mat/0701328 , 543kb)
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Paper: cond-mat/0701333
Date: Mon, 15 Jan 2007 14:58:52 GMT (966kb)

Title: Rapidly rotating boson molecules with long or short range repulsion: an
exact diagonalization study
Authors: Leslie O. Baksmaty, Constantine Yannouleas, Uzi Landman
Categories: cond-mat.mes-hall cond-mat.other
Comments: To appear in Physical Review A. REVTEX. 16 pages with 15 figures. For
related papers, see http://www.prism.gatech.edu/~ph274cy/
Subj-class: Mesoscopic Systems and Quantum Hall Effect; Other
\\
The Hamiltonian for a small number, N <= 11, of bosons in a rapidly rotating
harmonic trap, interacting via a short range (contact potential) or a long
range (Coulomb) interaction, is studied via an exact diagonalization in the
lowest Landau level. Our analysis shows that, for both low and high fractional
fillings, the bosons localize and form rotating boson molecules (RBMs)
consisting of concentric polygonal rings. Focusing on systems with the number
of trapped atoms sufficiently large to form multi-ring bosonic molecules, we
find that, as a function of the rotational frequency and regardless of the type
of repulsive interaction, the ground-state angular momenta grow in specific
steps that coincide with the number of localized bosons on each concentric
ring. Comparison of the conditional probability distributions (CPDs) for both
interactions suggests that the degree of crystalline correlations appears to
depend more on the fractional filling nu than on the range of the interaction.
The RBMs behave as nonrigid rotors, i.e., the concentric rings rotate
independently of each other. At filling fractions nu < 1/2, we observe well
developed crystallinity in the CPDs (two-point correlation functions). For
larger filling fractions nu > 1/2, observation of similar molecular patterns
requires consideration of even higher-order correlation functions.
\\ ( http://arXiv.org/abs/cond-mat/0701333 , 966kb)
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Paper: cond-mat/0701337
Date: Mon, 15 Jan 2007 17:34:44 GMT (45kb)

Title: Phase Diagram of Interacting Bosons on the Honeycomb Lattice
Authors: Stefan Wessel
Categories: cond-mat.other
Comments: 4 pages with 5 figures
Subj-class: Other
\\
We study the ground state properties of repulsively interacting bosons on the
honeycomb lattice using large-scale quantum Monte Carlo simulations. In the
hard-core limit the half-filled system develops long ranged diagonal order for
sufficiently strong nearest-neighbor repulsion. This staggered solid melts at a
first order quantum phase transition into the superfluid phase, without the
presence of any intermediate supersolid phase. Within the superfluid phase,
both the superfluid density and the compressibility exhibit local minima near
particle- (hole-) density one quarter, while the density and the condensate
fraction show inflection points in this region. Relaxing the hard-core
constraint, supersolid phases emerge for soft-core bosons. The suppression of
the superfluid density is found to persist for sufficiently large, finite
on-site repulsion.
\\ ( http://arXiv.org/abs/cond-mat/0701337 , 45kb)
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Paper: cond-mat/0701346
Date: Mon, 15 Jan 2007 19:41:59 GMT (8kb)

Title: Expansion of a Bose-Einstein Condensate in the Presence of Disorder
Authors: B. Shapiro
Categories: cond-mat.other
Subj-class: Other
\\
Spreading of a BEC in a weak disordered potential is studied. The BEC is
released from a trap, under the condition of strong nonlinearity, so that $\mu >> (\hbar/\tau)$, where $\mu$ is the chemical potential prior to the release
and $\tau$ is the mean transport time. The spread is controlled by the single
parameter $\mu\tau/hbar$.
\\ ( http://arXiv.org/abs/cond-mat/0701346 , 8kb)
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Paper: cond-mat/0701350
Date: Mon, 15 Jan 2007 20:37:12 GMT (377kb)

Title: Unitary polarized Fermi gases
Authors: Fr\'{e}d\'{e}ric Chevy (LKB - Lhomond)
Categories: cond-mat.stat-mech cond-mat.mes-hall
Comments: 15 pages, to be published in the proceedings of the 2006 Enrico Fermi
summer school on Fermi gases
Proxy: ccsd hal-00124717
Subj-class: Statistical Mechanics; Mesoscopic Systems and Quantum Hall Effect
\\
Although recent theoretical and experimental progress have considerably
clarified pairing mechanisms in spin 1/2 fermionic superfluid with equally
populated internal states, many open questions remain when the two spin
populations are mismatched. We show here that, taking advantage of the
universal behavior characterizing the regime of infinite scattering length, the
macroscopic properties of these systems can be simply and quantitatively
understood in the regime of strong interactions.
\\ ( http://arXiv.org/abs/cond-mat/0701350 , 377kb)
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Paper: quant-ph/0701080
Date: Sun, 14 Jan 2007 11:36:31 GMT (34kb)

Title: Manipulating Quantum States of Molecules Created via Photoassociation of
Bose-Einstein Condensates
Authors: Xiao-Ting Zhou, Xiong-Jun Liu, Hui Jing, C. H. Lai and C. H. Oh
Categories: quant-ph
\\
We show the quantum state transfer technique in two-color photoassociation
(PA) of a Bose-Einstein condensate, where a quantized field is used to couple
the free-bound transition from atom state to excited molecular state. Under the
weak excitation condition, we find that quantum states of the quantized field
can be transferred to the created molecular condensate. The feasibility of this
technique is confirmed by considering the atomic and molecular decays
discovered in the current PA experiments. The present results allow us to
manipulate quantum states of molecules in the photoassociation of a
Bose-Einstein condensate.
\\ ( http://arXiv.org/abs/quant-ph/0701080 , 34kb)
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Paper: quant-ph/0701094
Date: Mon, 15 Jan 2007 08:14:42 GMT (371kb)

Title: Optimal quantum control of Bose Einstein condensates in magnetic
microtraps
Authors: Ulrich Hohenester, Per Kristian Rekdal, Alfio Borzi, Joerg
Schmiedmayer
Categories: quant-ph
\\
Transport of Bose-Einstein condensates in magnetic microtraps, controllable
by external parameters such as wire currents or radio-frequency fields, is
studied within the framework of optimal control theory (OCT). We derive from
the Gross-Pitaevskii equation the optimality system for the OCT fields that
allow to efficiently channel the condensate between given initial and desired
states. For a variety of magnetic confinement potentials we study transport and
wavefunction splitting of the condensate, and demonstrate that OCT allows to
drastically outperfrom more simple schemes for the time variation of the
microtrap control parameters.
\\ ( http://arXiv.org/abs/quant-ph/0701094 , 371kb)
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Paper: cond-mat/0701364
Date: Tue, 16 Jan 2007 07:33:15 GMT (241kb)

Title: Localization of a Bose Einstein condensate in an optical superlattice
Authors: Aranya B Bhattacherjee
Categories: cond-mat.stat-mech
Subj-class: Statistical Mechanics
\\
The Bloch and dipole oscillations of a Bose Einstein condensate (BEC) in an
optical superlattice is investigated. We show that the effective mass increases
in an optical superlattice, which leads to localization of the BEC, in
accordance with recent experimental observations. In addition, we find that the
secondary optical lattice is a useful additional tool to manipulate localized
excitations.
\\ ( http://arXiv.org/abs/cond-mat/0701364 , 241kb)
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Paper: cond-mat/0701365
Date: Tue, 16 Jan 2007 08:14:41 GMT (23kb)

Title: Spontaneous Symmetry Breaking in Superfluid Helium-4
Categories: cond-mat.other
Subj-class: Other
\\
We derive an analytical expression for a critical temperature of spontaneous
symmetry breaking in a repulsive hard-core interacting Bose system. We show
that the critical temperature of spontaneous symmetry breaking in a hard-core
interacting Bose system is determined by the three physical parameters: the
density of Bose liquid at absolute zero (rho_0), the mass (m) and the hard
sphere diameter (sigma) of a boson. The formula that we have derived is Tc =
rho_0 pi hbar^2 sigma / m^2 kB. We report Tc of liquid helium-4 is 2.194 K,
which is significantly close to the lambda temperature of 2.1768 K. The
deviation between the predicted and experimental values of the lambda
temperature is less than 1%.
\\ ( http://arXiv.org/abs/cond-mat/0701365 , 23kb)
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Paper: cond-mat/0701383
Date: Tue, 16 Jan 2007 17:42:16 GMT (254kb)

Title: Classical and quantum features of the superfluid to Mott insulator
transition
Authors: D. Witthaut, F. Trimborn, and H. J. Korsch
Categories: cond-mat.other
Subj-class: Other
\\
We analyze the correspondence of many-particle and mean-field dynamics for a
Bose-Einstein condensate in an optical lattice. Representing many-particle
quantum states by a classical phase space ensemble instead of one single
mean-field trajectory and taking into account the quantization of the density
by a modified integer Gross-Pitaevskii equation, it is possible to simulate the
superfluid to Mott insulator transition and other phenomena purely classically.
This approach can be easily extended to higher particle numbers and
multidimensional lattices. Moreover it provides an excellent tool to classify
true quantum features and to analyze the mean-field -- many particle
correspondence.
\\ ( http://arXiv.org/abs/cond-mat/0701383 , 254kb)
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Paper: cond-mat/0701384
Date: Tue, 16 Jan 2007 17:52:05 GMT (120kb)

Title: Multiscale quantum-defect theory for two interacting atoms in a
symmetric harmonic trap
Authors: Yujun Chen and Bo Gao
Categories: cond-mat.stat-mech
Subj-class: Statistical Mechanics
\\
We present a multiscale quantum-defect theory (QDT) for two identical atoms
in a symmetric harmonic trap that combines the quantum-defect theory for the
van der Waals interaction [B. Gao, Phys. Rev. A \textbf{64}, 010701(R) (2001)]
at short distances with a quantum-defect theory for the harmonic trapping
potential at large distances. The theory provides a systematic understanding of
two atoms in a trap, from deeply bound molecular states and states of different
partial waves, to highly excited trap states. It shows, e.g., that a strong $p$
wave pairing can lead to a lower energy state around the threshold than a $s$
wave pairing.
\\ ( http://arXiv.org/abs/cond-mat/0701384 , 120kb)
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Paper: quant-ph/0701110
Date: Tue, 16 Jan 2007 14:14:41 GMT (119kb)

Title: Preparing and probing atomic number states with an atom interferometer
Authors: J. Sebby-Strabley, B. L. Brown, M. Anderlini, P. J. Lee, P. R.
Johnson, W. D. Phillips, and J. V. Porto
Categories: quant-ph
\\
and Poisson states of atoms in individual sites of a double well optical
lattice. These states are input to an atom interferometer that is realized by
symmetrically splitting individual lattice sites into double wells, allowing
atoms in individual sites to evolve independently. The two paths then
interfere, creating a matter-wave double-slit diffraction pattern. The time
evolution of the double-slit diffraction pattern is used to measure the number
statistics of the input state. The flexibility of our double well lattice
provides a means to detect the presence of empty lattice sites, an important
and so far unmeasured factor in determining the purity of a Mott state.
\\ ( http://arXiv.org/abs/quant-ph/0701110 , 119kb)
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Paper: cond-mat/0701390
Date: Tue, 16 Jan 2007 22:10:38 GMT (94kb)

Title: Propagation of short pulses through a Bose-Einstein condensate
Authors: Devrim Tarhan, Seckin Sefi, Ozgur E. Mustecaplioglu
Categories: cond-mat.other
Subj-class: Other
Journal-ref: published in J. Phys.: Conf. Ser. 36 194-199 (2006)
\\
We study propagation of short laser pulses in a Bose-Einstein condensate
taking into account dispersive effects under the conditions for
electromagnetically induced transparency. We calculate dispersion coefficients
using typical experimental parameters of slow-light schemes in condensates. By
numerically propagating the laser pulse, and referring to theoretical
estimations, we determine the conditions for which dispersion starts to
introduce distortions on the pulse shape.
\\ ( http://arXiv.org/abs/cond-mat/0701390 , 94kb)
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Paper: cond-mat/0701407
Date: Wed, 17 Jan 2007 11:13:32 GMT (33kb)

Title: Bose-Einstein-condensed gases with arbitrary strong interactions
Authors: V.I. Yukalov and E.P. Yukalova
Categories: cond-mat.stat-mech
Comments: Latex file, 23 pages, 4 figures
Subj-class: Statistical Mechanics
Journal-ref: Phys. Rev. A 74 (2006) 063623-9
\\
Bose-condensed gases are considered with an effective interaction strength
varying in the whole range of the values between zero and infinity. The
consideration is based on the usage of a representative statistical ensemble
for Bose systems with broken global gauge symmetry. Practical calculations are
illustrated for a uniform Bose gas at zero temperature, employing a
self-consistent mean-field theory, which is both conserving and gapless.
\\ ( http://arXiv.org/abs/cond-mat/0701407 , 33kb)
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Paper: cond-mat/0701411
Date: Wed, 17 Jan 2007 13:31:19 GMT (209kb)

Title: Self-induced density modulations in the free expansion of Bose-Einstein
condensates
Authors: L. Salasnich, N. Manini, F. Bonelli, M. Korbman, and A. Parola
Categories: cond-mat.other cond-mat.stat-mech
Subj-class: Other; Statistical Mechanics
\\
We simulate numerically the free expansion of a repulsive Bose-Einstein
condensate with an initially Gaussian density profile. We find a self-similar
expansion only for weak inter-atomic repulsion. In contrast, for strong
repulsion we observe the spontaneous formation of a shock wave at the surface
followed by a significant depletion inside the cloud. In the expansion,
contrary to the case of a classical viscous gas, the quantum fluid can generate
radial rarefaction density waves with several minima and maxima. These
intriguing nonlinear effects, never observed yet in free-expansion experiments
with ultra-cold alkali-metal atoms, can be detected with the available setups.
\\ ( http://arXiv.org/abs/cond-mat/0701411 , 209kb)
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Paper: cond-mat/0701416
Date: Wed, 17 Jan 2007 16:29:01 GMT (596kb)

Title: Quantum Theory of Cavity-Assisted Sideband Cooling of Mechanical Motion
Authors: Florian Marquardt, Joe P. Chen, A. A. Clerk, S. M. Girvin
Categories: cond-mat.mes-hall
Subj-class: Mesoscopic Systems and Quantum Hall Effect
\\
We present a fully quantum theory describing the cooling of a cantilever
coupled via radiation pressure to an illuminated optical cavity. Applying the
quantum noise approach to the fluctuations of the radiation pressure force, we
derive the opto-mechanical cooling rate and the minimum achievable phonon
number. We find that reaching the quantum limit of arbitrarily small phonon
numbers requires going into the good cavity (resolved phonon sideband) regime
where the cavity linewidth is much smaller than the mechanical frequency and
the corresponding cavity detuning. This is in contrast to the common assumption
that the mechanical frequency and the cavity detuning should be comparable to
the cavity damping.
\\ ( http://arXiv.org/abs/cond-mat/0701416 , 596kb)
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Paper: cond-mat/0701420
Date: Wed, 17 Jan 2007 19:00:59 GMT (15kb)

Title: Visibility of a Bose-condensed gas released from an optical lattice at
finite temperatures
Authors: Fabrice Gerbier, Simon Foelling, Artur Widera, Immanuel Bloch
Categories: cond-mat.stat-mech
Comments: Response to cond-mat/0609685; 5pages, 2 figures
Subj-class: Statistical Mechanics
\\
In response to a recent manuscript [cond-mat/0609685] on the analysis of
interference patterns produced by ultracold atoms released from an optical
lattice, we point out that in the presence of a Bose-Einstein condensate the
interference pattern can be strongly modified by interaction effects and the
presence of a harmonic trap superimposed on the lattice potential. Our results
show that the visibility of the interference pattern is significant only if a
sizeable condensate fraction is present in the trap.
\\ ( http://arXiv.org/abs/cond-mat/0701420 , 15kb)
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Paper: physics/0701191
Date: Tue, 16 Jan 2007 22:54:21 GMT (62kb)

Title: Increasing the coherence time of Bose-Einstein-condensate
interferometers with optical control of dynamics
Authors: James Stickney, Dana Z. Anderson, Alex Zozulya
Categories: physics.atom-ph
Subj-class: Atomic Physics
\\
Atom interferometers using Bose-Einstein condensate that is confined in a
waveguide and manipulated by optical pulses have been limited by their short
coherence times. We present a theoretical model that offers a physically simple
explanation for the loss of contrast and propose the method for increasing the
fringe contrast by recombining the atoms at a different time. A simple,
quantitatively accurate, analytical expression for the optimized recombination
time is presented and used to place limits on the physical parameters for which
the contrast may be recovered.
\\ ( http://arXiv.org/abs/physics/0701191 , 62kb)
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Paper: physics/0701194
Date: Wed, 17 Jan 2007 12:05:04 GMT (76kb)

Title: Heteronuclear ionizing collisions between laser-cooled metastable helium
atoms
Authors: J. M. McNamara, R. J. W. Stas, W. Hogervorst, and W. Vassen
Categories: physics.atom-ph
Subj-class: Atomic Physics
\\
We have investigated cold ionizing heteronuclear collisions in dilute
mixtures of metastable (2 3S1) 3He and 4He atoms, extending our previous work
on the analogous homonuclear collisions [R. J. W. Stas et al., PRA 73, 032713
(2006)]. A simple theoretical model of such collisions enables us to calculate
the heteronuclear ionization rate coefficient, for our quasi-unpolarized gas,
in the absence of resonant light (T = 1.2 mK): K34(th) = 2.4*10^-10 cm^3/s.
This calculation is supported by a measurement of K34 using magneto-optically
trapped mixtures containing about 1*10^8 atoms of each species, K34(exp) =
2.5(8)*10^-10 cm^3/s. Theory and experiment show good agreement.
\\ ( http://arXiv.org/abs/physics/0701194 , 76kb)
------------------------------------------------------------------------------
\\
Paper: cond-mat/0701421
Date: Wed, 17 Jan 2007 21:13:34 GMT (425kb)

Title: Linear response theory for a pair of coupled one-dimensional condensates
of interacting atoms
Authors: Vladimir Gritsev, Anatoli Polkovnikov, Eugene Demler
Categories: cond-mat.other
Subj-class: Other
\\
We use quantum sine-Gordon model to describe the low energy dynamics of a
pair of coupled one-dimensional condensates of interacting atoms. We show that
the nontrivial excitation spectrum of the quantum sine-Gordon model, which
includes soliton and breather excitations, can be observed in experiments with
time-dependent modulation of the tunneling amplitude, potential difference
between condensates, or phase of tunneling amplitude. We use the form-factor
approach to compute structure factors corresponding to all three types of
perturbations.
\\ ( http://arXiv.org/abs/cond-mat/0701421 , 425kb)
------------------------------------------------------------------------------
\\
Paper: cond-mat/0701437
Date: Thu, 18 Jan 2007 09:28:13 GMT (108kb)

Title: On the theory of Bose-Einstein condensation of quasiparticles: on the
possibility of condensation of magnons at high temperatures
Authors: A.I. Bugrij and V.M. Loktev
Categories: cond-mat.stat-mech
Subj-class: Statistical Mechanics
Journal-ref: Low Temp. Phys. v.33, No 1 (January) (2007)
\\
Bose condensation of quasiparticles in physical systems of finite size iz
considered for the case of ferromagnetic thin films. It is shown that in
accordance with present-day experimental capabilities which permit one to
achieve densities of long-wave spin excitation of 1018-1019 cm-3, in such films
the formation of condensate of such quasiparticles begins at temperatures T~100
K (room one including). It is found that Bose condensation is accompanied by
scaling phenomenon according to which the main thermodynamic variable is not
the number N of particles but the ratio N/T. This indicates that condensation
of magnons can be observed at relatively low magnon densities. The roles played
by the shape of the spectrum and film thickness are analyzed.
\\ ( http://arXiv.org/abs/cond-mat/0701437 , 108kb)
------------------------------------------------------------------------------
\\
Paper: cond-mat/0701439
Date: Thu, 18 Jan 2007 09:50:52 GMT (51kb)

Title: Quantum vortices in optical lattices
Authors: P. Vignolo (INFN Pisa, Italy), R. Fazio (SISSA Trieste and SNS Pisa,
Italy) and M.P. Tosi (SNS Pisa, Italy)
Categories: cond-mat.soft
Subj-class: Soft Condensed Matter
\\
A vortex in a superfluid gas inside an optical lattice can behave as a
massive particle moving in a periodic potential and exhibiting quantum
properties. In this Letter we discuss these properties and show that the
excitation of vortex motions in a two-dimensional lattice can lead to striking
measurable changes in its dynamic response. It would be possible by means of
Bragg spectroscopy to carry out the first direct measurement of the effective
vortex mass, the pinning to the underlying lattice, and the dissipative
damping.
\\ ( http://arXiv.org/abs/cond-mat/0701439 , 51kb)
------------------------------------------------------------------------------
\\
Paper: cond-mat/0701441
Date: Thu, 18 Jan 2007 10:28:07 GMT (53kb)

Title: Quantum Monte Carlo study of a 1D phase-fluctuating condensate
Authors: C. Gils, L. Pollet, A. Vernier, F. Hebert, G.G. Batrouni, M. Troyer
Categories: cond-mat.stat-mech
Subj-class: Statistical Mechanics
\\
We study numerically the low temperature behaviour of a 1D Bose gas trapped
in an optical lattice. For a sufficient number of particles and weak repulsive
interactions, we find a clear regime of temperatures where density fluctuations
are negligible but phase fluctuations are considerable, i.e., a
quasicondensate. In the weakly interacting limit, our results are in very good
agreement with those obtained using a mean-field approximation. In coupling
regimes beyond the validity of mean-field approaches, a phase-fluctuating
condensate also appears, but the phase-correlation properties are qualitatively
different. It is shown that quantum depletion plays an important role.
\\ ( http://arXiv.org/abs/cond-mat/0701441 , 53kb)
------------------------------------------------------------------------------
\\
Paper: cond-mat/0701446
Date: Thu, 18 Jan 2007 12:26:36 GMT (9kb)

Title: Enhancing capacity of coherent optical information storage and transfer
in a Bose-Einstein condensate
Authors: Ozgur E. Mustecaplioglu, Devrim Tarhan
Categories: cond-mat.other
Comments: 12pages. Laser Physics, in press
Subj-class: Other
\\
Coherent optical information storage capacity of an atomic Bose-Einstein
condensate is examined. Theory of slow light propagation in atomic clouds is
generalized to short pulse regime by taking into account group velocity
dispersion. It is shown that the number of stored pulses in the condensate can
be optimized for a particular coupling laser power, temperature and interatomic
interaction strength. Analytical results are derived for semi-ideal model of
the condensate using effective uniform density zone approximation. Detailed
numerical simulations are also performed. It is found that axial density
profile of the condensate protects the pulse against the group velocity
dispersion. Furthermore, taking into account finite radial size of the
condensate, multi-mode light propagation in atomic Bose-Einstein condensate is
investigated. The number of modes that can be supported by a condensate is
found. Single mode condition is determined as a function of experimentally
accessible parameters including trap size, temperature, condensate number
density and scattering length. Quantum coherent atom-light interaction schemes
are proposed for enhancing multi-mode light propagation effects.
\\ ( http://arXiv.org/abs/cond-mat/0701446 , 9kb)
------------------------------------------------------------------------------
\\
Paper: cond-mat/0701450
Date: Thu, 18 Jan 2007 15:06:26 GMT (20kb)

Title: More Accurate Theory for Bose-Einstein Condensation Fraction
Authors: Shyamal Biswas
Categories: cond-mat.stat-mech
Subj-class: Statistical Mechanics
\\
In the thermodynamic limit the ratio of system size to thermal de Broglie
wavelength tends to infinity and the volume per particle of the system is
constant. Our familiar Bose-Einstein statistics is absolutely valid in the
thermodynamic limit. For finite thermodynamical system this ratio as well as
the number of particles is much greater than 1. However, according to the
experimental setup of Bose-Einstein condensation of harmonically trapped Bose
gas of alkali atoms this ratio near the condensation temperature($T_c$) is
$\sim 32$ and at ultralow temperatures well below $T_c$ a large fraction of
particles come down to the single particle ground state, and this ratio becomes
comparable to 1. We justify the finite size as well as ultralow temperature
correction to Bose-Einstein statistics. From this corrected statistics we plot
condensation fraction versus temperature graph. This theoretical plot satisfies
well with the experimental plot(A. Griesmaier et al..,Phys.Rev.Lett. \
{\bf{{94}}}{(2005){160401}}).
\\ ( http://arXiv.org/abs/cond-mat/0701450 , 20kb)
------------------------------------------------------------------------------
\\
Paper: quant-ph/0701127
Date: Wed, 17 Jan 2007 22:07:32 GMT (28kb)

Title: The Physical Basis of the Gibbs-von Neumann entropy
Authors: O. J. E. Maroney
Categories: quant-ph
Comments: 34 pages, no figures (2nd version corrects bibliography error)
Report-no: pi-foundqt-36
\\
We develop the argument that the Gibbs-von Neumann entropy is the appropriate
statistical mechanical generalisation of the thermodynamic entropy, for
macroscopic and microscopic systems, whether in thermal equilibrium or not, as
a consequence of Hamiltonian dynamics. The mathematical treatment builds upon
well know results \cite{Gib1902,Tol1938,Weh78,Par89b}, and most importantly,
extends the arguments of \cite{Szi1925} to quantum mechanics. This enables the
identification of the canonical distribution as the unique representation of
thermal states, independant of any other thermodynamic considerations. The
Gibbs-von Neumann entropy can then be derived, from arguments based solely on
the addition of probabilities to Hamiltonian dynamics.
\\ ( http://arXiv.org/abs/quant-ph/0701127 , 28kb)
------------------------------------------------------------------------------
\\
Paper: quant-ph/0701130
Date: Thu, 18 Jan 2007 16:53:17 GMT (17kb)

Title: Entanglement between two fermionic atoms inside a cylindrical harmonic
trap
Authors: B. Sun, D. L. Zhou, L. You
Categories: quant-ph
\\
We investigate quantum entanglement between two (spin-1/2) fermions inside a
cylindrical harmonic trap, making use of the von Neumann entropy for the
reduced single particle density matrix as the pure state entanglement measure.
We explore the dependence of pair entanglement on the geometry and strength of
the trap and on the strength of the pairing interaction over the complete range
of the effective BCS to BEC crossover. Our result elucidates an interesting
connection between our model system of two fermions and that of two interacting
bosons.
\\ ( http://arXiv.org/abs/quant-ph/0701130 , 17kb)
------------------------------------------------------------------------------
\\
Paper: quant-ph/0701132
Date: Thu, 18 Jan 2007 13:04:24 GMT (715kb)

Title: Topological stability of stored optical vortices
Authors: R. Pugatch, M. Shuker, O. Firstenberg, A. Ron, N. Davidson
\\
We report an experiment in which an optical vortex is stored in a vapor of Rb
atoms. Due to its 2\pi phase twist, this mode, also known as the Laguerre-Gauss
mode, is topologically stable and cannot unwind even under conditions of strong
diffusion. To supplement our finding, we stored a flat phase Gaussian beam with
a dark center. Contrary to the optical vortex, which stays stable for over 100
microseconds, the dark center in the retrieved flat-phased image was filled
with light at storage times as small as 10 microseconds. This experiment proves
that higher electromagnetic modes can be converted into atomic coherences, and
that modes with phase singularities are robust to decoherence effects such as
diffusion. This opens the possibility to more elaborate schemes for two
dimensional information storage in atomic vapors.
\\ ( http://arXiv.org/abs/quant-ph/0701132 , 715kb)
------------------------------------------------------------------------------
\\
Paper: quant-ph/0701133
Date: Thu, 18 Jan 2007 16:06:53 GMT (193kb)

Title: Trapping of light pulses in ensembles of stationary Lambda atoms
Authors: Kristian Rymann Hansen and Klaus Molmer
Categories: quant-ph
\\
We present a detailed theoretical description of the generation of stationary
light pulses by standing wave electromagnetically induced transparency in media
comprised of stationary atoms. We show that, contrary to thermal gas media, the
achievable storage times are limited only by the ground state dephasing rate of
the atoms, making such media ideally suited for nonlinear optical interactions
between stored pulses. Furthermore, we find significant quantitative and
qualitative differences between the two types of media, which are important for
quantum information processing schemes involving stationary light pulses.
\\ ( http://arXiv.org/abs/quant-ph/0701133 , 193kb)
------------------------------------------------------------------------------
\\
Paper: physics/0701217
Date: Thu, 18 Jan 2007 16:27:55 GMT (65kb)

Title: Pseudo-potential treatment of two aligned dipoles under external
harmonic confinement
Authors: K. Kanjilal, J. L. Bohn, and D. Blume
Categories: physics.atom-ph
Subj-class: Atomic Physics
\\
Dipolar Bose and Fermi gases, which are currently being studied extensively
experimentally and theoretically, interact through anisotropic, long-range
potentials. Here, we replace the long-range potential by a zero-range
pseudo-potential that simplifies the theoretical treatment of two dipolar
particles in a harmonic trap. Our zero-range pseudo-potential description
reproduces the energy spectrum of two dipoles interacting through a
shape-dependent potential under external confinement very well, provided that
classification scheme of the energy spectrum in terms of approximate angular
momentum quantum numbers. The results may be directly relevant to the physics
of dipolar gases loaded into optical lattices.
\\ ( http://arXiv.org/abs/physics/0701217 , 65kb)
------------------------------------------------------------------------------

Replacements:

------------------------------------------------------------------------------
\\
Paper: cond-mat/0606151
replaced with revised version Fri, 12 Jan 2007 19:18:21 GMT (67kb)

Title: Structure of vortices in rotating Bose-Einstein condensates
Authors: Gentaro Watanabe, S. Andrew Gifford, Gordon Baym, C. J. Pethick
Categories: cond-mat.other cond-mat.mes-hall
Comments: 10 pages, 9 figures, published version
Report-no: NORDITA-2006-15
Subj-class: Other; Mesoscopic Systems and Quantum Hall Effect
Journal-ref: Phys. Rev. A 74, 063621 (2006)
DOI: 10.1103/PhysRevA.74.063621
\\ ( http://arXiv.org/abs/cond-mat/0606151 , 67kb)
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\\
Paper: cond-mat/0607776
replaced with revised version Thu, 11 Jan 2007 21:40:03 GMT (72kb)

Title: The potential energy of a $^{40}$K Fermi gas in the BCS-BEC crossover
Authors: J. T. Stewart, J. P. Gaebler, C. A. Regal, and D. S. Jin
Categories: cond-mat.other
Subj-class: Other
Journal-ref: Phys. Rev. Lett. 97, 220406 (2006)
\\ ( http://arXiv.org/abs/cond-mat/0607776 , 72kb)
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\\
Paper: cond-mat/0611645
replaced with revised version Fri, 12 Jan 2007 11:16:57 GMT (44kb)

Title: Classical field techniques for condensates in one-dimensional rings at
finite temperatures
Authors: A. Nunnenkamp, J. N. Milstein and K. Burnett
Categories: cond-mat.other
Subj-class: Other
\\ ( http://arXiv.org/abs/cond-mat/0611645 , 44kb)
------------------------------------------------------------------------------
\\
Paper: cond-mat/0701057
replaced with revised version Thu, 11 Jan 2007 21:08:10 GMT (23kb)

Title: Using time reversal symmetry for sensitive incoherent matter-wave Sagnac
interferometry
Authors: Y. Japha, O. Arzouan, Y. Avishai and R. Folman
Categories: cond-mat.other
Subj-class: Other
\\ ( http://arXiv.org/abs/cond-mat/0701057 , 23kb)
------------------------------------------------------------------------------
\\
Paper: cond-mat/0604673
replaced with revised version Sun, 14 Jan 2007 16:36:00 GMT (272kb)

Title: Evolution from a Bose-Einstein condensate to a Tonks-Girardeau gas: An
exact diagonalization study
Authors: Frank Deuretzbacher, Kai Bongs, Klaus Sengstock, Daniela Pfannkuche
Categories: cond-mat.other
Subj-class: Other
Journal-ref: Phys. Rev. A 75, 013614 (2007)
DOI: 10.1103/PhysRevA.75.013614
\\ ( http://arXiv.org/abs/cond-mat/0604673 , 272kb)
------------------------------------------------------------------------------
\\
Paper: cond-mat/0607098
replaced with revised version Tue, 16 Jan 2007 01:59:58 GMT (31kb)

Title: Critical velocities for a superfluid in a periodic potential
Authors: Biao Wu and Junren Shi
Categories: cond-mat.supr-con
Comments: extensive revision, 4 pages and 4 figures
Subj-class: Superconductivity
\\ ( http://arXiv.org/abs/cond-mat/0607098 , 31kb)
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\\
Paper: cond-mat/0612544
replaced with revised version Tue, 16 Jan 2007 06:15:52 GMT (206kb)

Title: Ground states of hard-core bosons in one dimensional periodic potentials
Authors: Yuan Lin and Biao Wu
Categories: cond-mat.other
Subj-class: Other
\\ ( http://arXiv.org/abs/cond-mat/0612544 , 206kb)
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\\
Paper: cond-mat/0610644
replaced with revised version Thu, 18 Jan 2007 08:10:58 GMT (178kb)

Title: Non-diffusive phase spreading of a Bose-Einstein condensate at finite
temperature
Authors: Alice Sinatra (LKB - Lhomond), Yvan Castin (LKB - Lhomond), Emilia
Witkowska
Categories: cond-mat.other
Proxy: ccsd hal-00109021
Subj-class: Other
\\ ( http://arXiv.org/abs/cond-mat/0610644 , 178kb)
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\\
Paper: cond-mat/0611230
replaced with revised version Thu, 18 Jan 2007 20:35:34 GMT (16kb)

Title: Classifying Vortices in S=3 Bose-Einstein Condensates
Authors: Ryan Barnett, Ari Turner, Eugene Demler
Categories: cond-mat.str-el
Subj-class: Strongly Correlated Electrons
\\ ( http://arXiv.org/abs/cond-mat/0611230 , 16kb)
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\\
Paper: cond-mat/0612664
replaced with revised version Thu, 18 Jan 2007 14:52:44 GMT (67kb)

Title: Vortex quantum creation and winding number scaling in a quenched spinor
Bose gas
Authors: Michael Uhlmann, Ralf Sch\"utzhold, and Uwe R. Fischer
Categories: cond-mat.other
Comments: 4 pages of RevTex4, 2 figures; a few modifications, changed Fig. 2
Subj-class: Other
\\ ( http://arXiv.org/abs/cond-mat/0612664 , 67kb)
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\\
Paper: quant-ph/0603016
replaced with revised version Thu, 18 Jan 2007 08:58:31 GMT (107kb)

Title: Quantum correlations of two optical fields close to electromagnetically
induced transparency
Authors: Alice Sinatra (LKB - Lhomond)
Categories: quant-ph
Proxy: ccsd ccsd-00019947
Journal-ref: Physical review letters 97 (19/12/2006) 253601
\\ ( http://arXiv.org/abs/quant-ph/0603016 , 107kb)
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Next week follows soon.
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 Fri Feb 02 2007 - 05:24:32 EST

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