# Matt's arXiv selection, Tuesday 20th June 2006

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Tue, 20 Jun 2006 09:17:38 +1000 (EST)

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

Hi all,

Apologies for being a day late yet again... I have included the first mailing
from this week as well.

The abstracts:

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Paper: cond-mat/0606226
Date: Fri, 9 Jun 2006 00:42:28 GMT (75kb)

Title: Josephson effect and quantum merging of two Bose superfluids
Authors: Hongwei Xiong, Shujuan Liu, Mingsheng Zhan
Subj-class: Superconductivity; Other
Journal-ref: PHYSICAL REVIEW B 73, 224505 (2006)
\\
We consider the Josephson effect when two independent Bose superfluids are
weakly connected. In the presence of interparticle interaction and based on the
calculations of the one-particle density matrix of the whole system, we find
that the one-particle density matrix can be factorized which satisfies the
general criterion of Bose superfluid proposed by Penrose and Onsager. By
introducing an effective order parameter for the whole system, our researches
show that there is Josephson effect for two independent Bose superfluids.
\\ ( http://arXiv.org/abs/cond-mat/0606226 , 75kb)
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Paper: cond-mat/0606243
Date: Fri, 9 Jun 2006 13:39:29 GMT (304kb)

Title: A 'Wheel' and 'Axle' description of the Bogoliubov-Anderson phonon in
the BEC/BCS crossover
Authors: Da-Shin Lee, Chi-Yong Lin and Ray J. Rivers
Subj-class: Other
\\
We show that the properties of the gapless mode of the BEC/BCS crossover in
the presence of a Feshbach resonance at T=0 can be derived easily from the
derivative expansion of the exact (one-loop) effective action. In particular,
from a simple 'wheel' and 'axle' phonon action, we calculate the sound
velocity, both analytically and numerically, throughout the BCS and BEC
regimes.
\\ ( http://arXiv.org/abs/cond-mat/0606243 , 304kb)
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Paper: cond-mat/0606255
Date: Fri, 9 Jun 2006 19:13:00 GMT (316kb)

Title: Bose-Fermi mixtures in 1D optical superlattices
Authors: F. Schmitt, M. Hild, R. Roth
Subj-class: Statistical Mechanics
\\
The zero temperature phase diagram of binary boson-fermion mixtures in
two-colour superlattices is investigated. The eigenvalue problem associated
with the Bose-Fermi-Hubbard Hamiltonian is solved using an exact numerical
diagonalization technique, supplemented by an adaptive basis truncation scheme.
The physically motivated basis truncation allows to access larger systems in a
fully controlled and very flexible framework. Several experimentally relevant
observables, such as the matter-wave interference pattern and the
condensatefraction, are investigated in order to explore the rich phase
diagram. At symmetric half filling a phase similar to the Mott-insulating phase
in a commensurate purely bosonic system is identified and an analogy to recent
experiments is pointed out. Furthermore a phase of complete localization of the
bosonic species generated by the repulsive boson-fermion interaction is
identified. These localized condensates are of a different nature than the
genuine Bose-Einstein condensates in optical lattices.
\\ ( http://arXiv.org/abs/cond-mat/0606255 , 316kb)
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Paper: quant-ph/0606065
Date: Thu, 8 Jun 2006 03:39:59 GMT (52kb)

Title: Perfect quantum state transfer with spinor bosons on weighted graphs
Authors: David L. Feder
Comments: 4 pages, 2 figures, revtex
Subj-class: Quantum Physics; Other
\\
A duality between the properties of many spinor bosons on a regular lattice
and those of a single particle on a weighted graph reveals that a quantum
particle can traverse an infinite hierarchy of networks with perfect
probability in polynomial time, even as the number of nodes increases
exponentially. The one-dimensional quantum wire' and the hypercube are special
cases in this construction, where the number of spin degrees of freedom is
equal to one and the number of particles, respectively. An implementation of
near-perfect quantum state transfer across a weighted parallelepiped with
ultracold atoms in optical lattices is discussed.
\\ ( http://arXiv.org/abs/quant-ph/0606065 , 52kb)
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Paper: quant-ph/0606074
Date: Thu, 8 Jun 2006 15:09:33 GMT (145kb)

Title: Conservative chaotic map as a model of quantum many-body environment
Authors: Davide Rossini, Giuliano Benenti, Giulio Casati
Subj-class: Quantum Physics; Statistical Mechanics; Chaotic Dynamics
\\
We study the dynamics of the entanglement between two qubits coupled to a
common chaotic environment, described by the quantum kicked rotator model. We
show that the kicked rotator, which is a single-particle deterministic
dynamical system, can reproduce the effects of a pure dephasing many-body bath.
Indeed, in the semiclassical limit the interaction with the kicked rotator can
be described as a random phase-kick, so that decoherence is induced in the
two-qubit system. We also show that our model can efficiently simulate
non-Markovian environments.
\\ ( http://arXiv.org/abs/quant-ph/0606074 , 145kb)
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Paper: cond-mat/0408460
replaced with revised version Fri, 9 Jun 2006 16:11:26 GMT (108kb)

Title: Vortices and Ring Solitons in Bose-Einstein Condensates
Authors: L. D. Carr and Charles W. Clark
Comments: 15 pages, 9 figures -- major revision
Subj-class: Other; Pattern Formation and Solitons
\\ ( http://arXiv.org/abs/cond-mat/0408460 , 108kb)
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Paper: cond-mat/0603319
replaced with revised version Fri, 9 Jun 2006 11:31:07 GMT (301kb)

Title: Simulations of ultracold bosonic atoms in optical lattices with
anharmonic traps
Authors: Olivier Gygi, Helmut G. Katzgraber, Matthias Troyer, Stefan Wessel,
and G. George Batrouni
Comments: 8 pages, 8 figures, 2 tables
Subj-class: Other
Journal-ref: Phys. Rev. A 73, 063606 (2006)
DOI: 10.1103/PhysRevA.73.063606
\\ ( http://arXiv.org/abs/cond-mat/0603319 , 301kb)
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Paper: quant-ph/0606082
Date: Fri, 9 Jun 2006 10:48:11 GMT (164kb)

Title: Microwave potentials and optimal control for robust quantum gates on an
atom chip
Authors: Philipp Treutlein, Theodor W. H\"ansch, Jakob Reichel, Antonio
Negretti, Markus A. Cirone, Tommaso Calarco
Comments: 14 pages, 7 figures, 1 table
\\
We propose a two-qubit collisional phase gate that can be implemented with
available atom chip technology, and present a detailed theoretical analysis of
its performance. The gate is based on earlier phase gate schemes, but uses a
qubit state pair with an experimentally demonstrated, very long coherence
lifetime. Microwave near-fields play a key role in our implementation as a
means to realize the state-dependent potentials required for conditional
dynamics. Quantum control algorithms are used to optimize gate performance. We
employ circuit configurations that can be built with current fabrication
processes, and extensively discuss the impact of technical noise and
imperfections that characterize an actual atom chip. We find an overall
infidelity compatible with requirements for fault-tolerant quantum computation.
\\ ( http://arXiv.org/abs/quant-ph/0606082 , 164kb)
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Paper: quant-ph/0606087
Date: Fri, 9 Jun 2006 14:54:05 GMT (234kb)

Title: Single atom quantum walk with 1D optical superlattices
Authors: Jaewoo Joo, P. L. Knight, and Jiannis K. Pachos
\\
A proposal for the implementation of quantum walks using cold atom technology
is presented. It consists of one atom trapped in time varying optical
superlattices. The required elements are presented in detail including the
preparation procedure, the manipulation required for the quantum walk evolution
and the final measurement. These procedures can be, in principle, implemented
with present technology.
\\ ( http://arXiv.org/abs/quant-ph/0606087 , 234kb)
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Paper: quant-ph/0605163
replaced with revised version Fri, 9 Jun 2006 13:13:14 GMT (617kb)

Title: Quantum Information Processing in Optical Lattices and Magnetic
Microtraps
Authors: Philipp Treutlein, Tilo Steinmetz, Yves Colombe, Benjamin Lev, Peter
Hommelhoff, Jakob Reichel, Markus Greiner, Olaf Mandel, Arthur Widera, Tim
Rom, Immanuel Bloch, and Theodor W. H\"ansch
Comments: 15 pages, 11 figures, corrected author list
\\ ( http://arXiv.org/abs/quant-ph/0605163 , 617kb)
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Paper: cond-mat/0606262
Date: Sat, 10 Jun 2006 14:04:49 GMT (191kb)

Title: One-dimensional description of a Bose-Einstein condensate in a rotating
closed-loop waveguide
Authors: S. Schwartz, M. Cozzini, C. Menotti, I. Carusotto, P. Bouyer, S.
Stringari
Subj-class: Other
\\
We propose a general procedure for reducing the three-dimensional Schrodinger
equation for atoms moving along a strongly confining atomic waveguide to an
effective one-dimensional equation. This procedure is applied to the case of a
rotating closed-loop waveguide. The possibility of including mean-field atomic
interactions is presented. Application of the general theory to characterize a
new concept of atomic waveguide based on optical tweezers is finally discussed.
\\ ( http://arXiv.org/abs/cond-mat/0606262 , 191kb)
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Paper: cond-mat/0606265
Date: Sat, 10 Jun 2006 19:45:04 GMT (177kb)

Title: Spinful bosons in an optical lattice
Authors: Sara Bergkvist, Ian McCulloch, Anders Rosengren
Subj-class: Other
\\
The phase diagram of spinful bosons in a one-dimensional optical lattice has
been obtained using density matrix renormalization group calculations.
Correlation functions and the dimerization are shown and we also present
results for the energy gap between ground state and the spin excited states. We
confirm the anticipated phase diagram, with Mott-insulating regions of
alternating dimerized S=1 chains for odd particle density versus on-site
singlets for even density. We find no evidence for any additional ordered
phases in the physically accessible region, however for sufficiently large spin
interaction, on-site singlet pairs dominate leading, for odd density, to a
breakdown of the Mott insulator or, for even density, a real-space singlet
superfluid.
\\ ( http://arXiv.org/abs/cond-mat/0606265 , 177kb)
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Paper: cond-mat/0606268
Date: Sun, 11 Jun 2006 00:18:12 GMT (881kb)

Title: Many-body studies on atomic quantum systems
Authors: Jordi Mur-Petit
Comments: PhD thesis with 216 pages and 48 figures; uses pdflatex. Some figures
have been submitted at low resolution to fit arXiv's memory limitations. The
http://www.tesisenxarxa.net/TDX-0426106-152454/
Subj-class: Other
\\
This thesis presents a set of studies on atomic systems where quantum effects
are particularly relevant. These studies have been developed by applying a
variety of tools from many-body physics.
First of all, we have studied the prospects for the existence of a superfluid
transition in an ultracold gas of fermionic atoms, by generalizing the BCS
theory of superconductivity to the case when the two species that pair have
different densities and the ground state may spontaneously break one or more
symmetries.
In a second part, we have studied the dynamics of a Bose-Einstein condensate
whose spin degree of freedom is free to evolve inside a quasi-onedimensional
optical trap. We have used a mean-field formulation to address both the zero
temperature case and the finite temperature one.
Finally, we have performed a careful study of the ground state and the line
tension of two-dimensional systems of helium-4. First, we have used Monte Carlo
techniques, then with a Density Functional built on-purpose.
KEYWORDS: Cold gases, Pairing, Spinor condensate, Helium, Two dimensions
\\ ( http://arXiv.org/abs/cond-mat/0606268 , 881kb)
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Paper: cond-mat/0606281
Date: Mon, 12 Jun 2006 12:58:54 GMT (886kb)

Title: A Primary Noise Thermometer for Ultracold Bose Gases
Authors: R. Gati, J. Esteve, B. Hemmerling, T. B. Ottenstein, J. Appmeier, A.
Weller, M. K. Oberthaler
Subj-class: Other
\\
We discuss in detail the experimental investigation of thermally induced
fluctuations of the relative phase between two weakly coupled Bose-Einstein
condensates. In analogy to superconducting Josephson junctions, the weak
coupling originates from a tunneling process through a potential barrier which
is obtained by trapping the condensates in an optical double-well potential.
The observed fluctuations of the relative phase are in quantitative agreement
with a many body two mode model at finite temperature. The agreement
demonstrates the possibility of using the phase fluctuation measurements in a
bosonic Josephson junction as a primary thermometer. This new method allows for
measuring temperatures far below the critical temperature where standard
methods based on time of flight measurements fail. We employ this new
thermometer to probe the heat capacity of a degenerate Bose gas as a function
of temperature.
\\ ( http://arXiv.org/abs/cond-mat/0606281 , 886kb)
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Paper: cond-mat/0606288
Date: Mon, 12 Jun 2006 15:13:46 GMT (47kb)

Title: Spontaneous Circulation in Ground-State Spinor Dipolar Bose-Einstein
Condensates
Authors: Yuki Kawaguchi, Hiroki Saito, and Masahito Ueda
Comments: 4 pages, 4 figures (include one color figure)
Subj-class: Other
\\
We have found three ground-state phases in a spin-1 ferromagnetic
Bose-Einstein condensate with magnetic dipole-dipole interactions. A
substantial orbital angular momentum accompanied by chiral symmetry breaking is
shown to spontaneously emerge in a certain parameter regime. All the phases can
be realized in the spin-1 $^{87}$Rb condensate by changing the number of atoms
or the trap frequency.
\\ ( http://arXiv.org/abs/cond-mat/0606288 , 47kb)
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Paper (*cross-listing*): nlin.PS/0606016
Date: Mon, 5 Jun 2006 20:52:31 GMT (12kb)

Title: On existence of dark solitons in cubic-quintic nonlinear Schr\"{o}dinger
equation with a periodic potential
Authors: Pedro J. Torres, Vladimir V. Konotop
Subj-class: Pattern Formation and Solitons; Chaotic Dynamics; Other
\\
A proof of existence of stationary dark soliton solutions of the
cubic-quintic nonlinear Schr\"{o}dinger equation with a periodic potential is
given. It is based on the interpretation of the dark soliton as a heteroclinic
on the Poincar\'e map.
\\ ( http://arXiv.org/abs/nlin/0606016 , 12kb)
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Paper: cond-mat/0603384
replaced with revised version Mon, 12 Jun 2006 11:59:46 GMT (103kb)

Title: Expansion of a Fermi Cloud in the BCS-BEC Crossover
Authors: Giovanni Diana, Nicola Manini, Luca Salasnich
Subj-class: Statistical Mechanics
Journal-ref: Phys. Rev. A 73, 065601 (2006)
\\ ( http://arXiv.org/abs/cond-mat/0603384 , 103kb)
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Paper: cond-mat/0605393
replaced with revised version Fri, 9 Jun 2006 20:49:10 GMT (113kb)

Title: Bose-Einstein condensates in RF-dressed adiabatic potentials
Authors: M. White, H. Gao, M. Pasienski, B. DeMarco
Subj-class: Other
\\ ( http://arXiv.org/abs/cond-mat/0605393 , 113kb)
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Paper: physics/0501146
replaced with revised version Fri, 9 Jun 2006 09:05:12 GMT (193kb)

Title: Quantum Accelerator Modes from the Farey Tree
Authors: A. Buchleitner, M. B. d'Arcy, S. Fishman, S. A. Gardiner, I. Guarneri,
Z.-Y. Ma, L. Rebuzzini, G. S. Summy
Subj-class: Atomic Physics; Chaotic Dynamics
Journal-ref: Phys. Rev. Lett. 96, 164101 (2006)
DOI: 10.1103/PhysRevLett.96.164101
\\ ( http://arXiv.org/abs/physics/0501146 , 193kb)
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Paper: cond-mat/0606319
Date: Tue, 13 Jun 2006 09:26:28 GMT (17kb)

Title: Off-diagonal correlations of lattice impenetrable bosons in one
dimension
Authors: D.M. Gangardt, G.V. Shlyapnikov
Comments: 10 pages. Submitted to the Focus Issue on 'Cold Atoms in Optical
Lattices' of New Journal of Physics
Subj-class: Statistical Mechanics
\\
We consider off-diagonal correlation functions of impenetrable bosons on a
lattice. By using the Jordan-Wigner transformation the one-body density matrix
is represented as (Toeplitz) determinant of a matrix of fermionic Green
functions. Using the replica method we calculate exactly the full long-range
asymptotic behaviour of the one-body density matrix. We discuss how subleading
oscillating terms, originating from short-range correlations give rise to
interesting features in the momentum distribution.
\\ ( http://arXiv.org/abs/cond-mat/0606319 , 17kb)
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Paper: cond-mat/0606322
Date: Tue, 13 Jun 2006 10:59:38 GMT (746kb)

Title: Finite Temperature Phase Diagram of a Two-Component Fermi Gas with
Density Imbalance
Authors: Lianyi He, Meng Jin and Pengfei Zhuang
Subj-class: Superconductivity; Other
\\
We investigated possible superfluid phases at finite temperature in a
two-component Fermi gas with density imbalance. In the frame of a general
four-fermion interaction theory, we solved the gap equations for the pairing
gap and pairing momentum under the restriction of fixed number densities, and
analyzed the stability of different phases by calculating the superfluid
density and number susceptibilities. The homogeneous superfluid is stable only
at high temperature and low number asymmetry, the inhomogeneous LOFF survives
at low temperature and high number asymmetry, and in between them there exists
another possible inhomogeneous phase, the phase separation. The critical
temperatures and the orders of the phase transitions among the superfluid
phases and normal phase are calculated analytically and numerically. The phase
diagram we obtained in the temperature and number asymmetry plane is quite
different from the one in temperature and chemical potential difference plane
for a system with fixed chemical potentials.
\\ ( http://arXiv.org/abs/cond-mat/0606322 , 746kb)
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Paper: cond-mat/0606327
Date: Tue, 13 Jun 2006 13:01:44 GMT (322kb)

Title: Single quantum realization of a collision of two Bose--Einstein
condensates
Authors: J. Chwedenczuk, P. Zin, K. Rzazewski and M. Trippenbach
Subj-class: Other
\\
We propose a method for simulating a single realization of a collision of two
Bose--Einstein condensates. Recently in Zi\'{n} {\it et al.} (Phys. Rev. Lett.
{\bf 94}, 200401 (2005)) we introduced a quantum model of an incoherent elastic
scattering in a collision of two counter-propagating atomic Gaussian
wavepackets. Here show that this model is capable of generating the data that
can be interpreted as results of a single collision event. We find a range of
parameters, including relative velocity, population and the size of colliding
condensates, where the structure of hallo of scattered atoms in a single
realization strongly differs from that averaged over many realizations.
\\ ( http://arXiv.org/abs/cond-mat/0606327 , 322kb)
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Paper: cond-mat/0606330
Date: Tue, 13 Jun 2006 14:41:46 GMT (622kb)

Title: Sarma Phase in Trapped Unbalanced Fermi Gases
Authors: K. B. Gubbels, M. W. J. Romans, and H. T. C. Stoof
Subj-class: Statistical Mechanics
\\
We consider a trapped unbalanced Fermi gas at nonzero temperatures where the
superfluid Sarma phase is stable. We determine in particular the phase
boundaries between the superfluid, normal, and phase separated regions of the
trapped unbalanced Fermi mixture. We show that the physics of the Sarma phase
is sufficient to understand the recent observations of Zwierlein et al.
[Science 311, 492 (2006); cond-mat/0605258] and indicate how the apparent
contradictions between this experiment and the experiment of Partridge et al.
[Science 311, 503 (2006)] may be resolved.
\\ ( http://arXiv.org/abs/cond-mat/0606330 , 622kb)
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Paper: quant-ph/0606097
Date: Mon, 12 Jun 2006 18:37:56 GMT (53kb)

Title: Strongly Interacting Polaritons in Coupled Arrays of Cavities
Authors: Michael J. Hartmann, Fernando G.S.L. Brandao and Martin B. Plenio
Subj-class: Quantum Physics; Other
\\
The experimental observation of quantum phenomena in strongly correlated many
particle systems is difficult because of the short length- and timescales
involved. Obtaining at the same time detailed control of individual
constituents appears even more challenging and thus to date inhibits employing
such systems as quantum computing devices. Substantial progress to overcome
these problems has been achieved with cold atoms in optical lattices, where a
detailed control of collective properties is feasible but it is very difficult
to address and hence control or measure individual sites. Here we show, that
polaritons, combined atom and photon excitations, in an array of cavities such
as a photonic crystal or coupled toroidal micro-cavities, can form a strongly
interacting many body system, where individual particles can be controlled and
measured. All individual building blocks of the proposed setting have already
been experimentally realised, thus demonstrating the potential of this device
as a quantum simulator.
\\ ( http://arXiv.org/abs/quant-ph/0606097 , 53kb)
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Paper: quant-ph/0606101
Date: Mon, 12 Jun 2006 21:57:28 GMT (14kb)

Title: Quantum Computation Using Vortices and Majorana Zero Modes of a $p_x$ +
$ip_y$ Superfluid of Fermionic Cold Atoms
Authors: Sumanta Tewari, S. Das Sarma, Chetan Nayak, Chuanwei Zhang, P. Zoller
\\
We propose to use the recently predicted two-dimensional weak-pairing' $p_x + ip_y$ superfluid state of fermionic cold atoms as a platform for topological
quantum computation. In the core of a vortex, this state supports a zero-energy
Majorana mode, which moves to finite energy in the corresponding topologically
trivial strong-pairing' state. By braiding vortices in the weak-pairing'
state, unitary quantum gates can be applied to the Hilbert space of Majorana
zero-modes. For read-out of the topological qubits, we propose realistic
schemes suitable for atomic superfluids.
\\ ( http://arXiv.org/abs/quant-ph/0606101 , 14kb)
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Paper: quant-ph/0606104
Date: Tue, 13 Jun 2006 03:13:54 GMT (144kb)

Title: Cooling to the Ground State of Axial Motion for One Atom Strongly
Coupled to an Optical Cavity
Authors: A. D. Boozer, A. Boca, R. Miller, T. E. Northup, H. J. Kimble
\\
Localization to the ground state of axial motion is demonstrated for a
single, trapped atom strongly coupled to the field of a high finesse optical
resonator. The axial atomic motion is cooled by way of coherent Raman
transitions on the red vibrational sideband. An efficient state detection
scheme enabled by strong coupling in cavity QED is used to record the Raman
spectrum, from which the state of atomic motion is inferred. We find that the
lowest vibrational level of the axial potential with zero-point energy 13uK is
occupied with probability P0~0.95.
\\ ( http://arXiv.org/abs/quant-ph/0606104 , 144kb)
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Paper: quant-ph/0606110
Date: Tue, 13 Jun 2006 13:57:39 GMT (17kb)

Title: Entanglement in Spin Waves with Binary Dipolar Atoms in a 2D Optical
Lattice
Authors: H. T. Ng and K. Burnett
\\
We study the area-dependent entropy and two-site entanglement in the spin
waves with binary interacting dipolar Bose-Einstein condensates in a 2D optical
lattice. The two species condensates at each site behave like an ensemble of
spin-half particles with the interaction to its nearest neighbors and next
nearest neighbors. We show that the ground state of a Bose-Einstein condensate
lattice with nearest-neighbor and next-nearest-neighbor interactions exhibits
spin wave and can be mapped into a harmonic lattice. The critical behavior of
the area-dependent entropy and two-site entanglement is examined in the
vicinity of a quantum phase transition.
\\ ( http://arXiv.org/abs/quant-ph/0606110 , 17kb)
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Paper: quant-ph/0606113
Date: Tue, 13 Jun 2006 16:17:02 GMT (353kb)

Title: Inserting two atoms into a single optical micropotential
Authors: Y. Miroshnychenko, W. Alt, I. Dotsenko, L. Foerster, M. Khudaverdyan,
D. Meschede, S. Reick, and A. Rauschenbeutel
\\
We recently demonstrated that strings of trapped atoms inside a standing wave
optical dipole trap can be rearranged using optical tweezers [Y. Miroshnychenko
et al., Nature, in press (2006)]. This technique allows us to actively set the
interatomic separations on the scale of the individual trapping potential
wells. Here, we use such a distance-control operation to insert two atoms into
the same potential well. The detected success rate of this manipulation is
16(+4/-3) %, in agreement with the predictions of a theoretical model based on
our independently determined experimental parameters.
\\ ( http://arXiv.org/abs/quant-ph/0606113 , 353kb)
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Paper: cond-mat/0606345
Date: Tue, 13 Jun 2006 23:25:13 GMT (310kb)

Title: First-principles quantum simulations of dissociation of molecular
condensates: Atom correlations in momentum space
Authors: C.M. Savage, P. Schwenn, K.V. Kheruntsyan
Subj-class: Other; Statistical Mechanics
\\
We investigate the quantum many-body dynamics of dissociation of a
Bose-Einstein condensate of molecular dimers into pairs of constituent bosonic
atoms and analyze the resulting atom-atom correlations. The quantum fields of
both the molecules and atoms are simulated from first principles in three
dimensions using the positive-P representation method. This allows us to
provide an exact treatment of the molecular field depletion and s-wave
scattering interactions between the particles, as well as to extend the
analysis to nonuniform systems. In the simplest uniform case, we find that the
major source of atom-atom decorrelation is atom-atom recombination which
produces molecules outside the initially occupied condensate mode. The unwanted
molecules are formed from dissociated atom pairs with non-opposite momenta. The
net effect of this process -- which becomes increasingly significant for
dissociation durations corresponding to more than about 40% conversion -- is to
reduce the atom-atom correlations. In addition, for nonuniform systems we find
that mode-mixing due to inhomogeneity can result in further degradation of the
correlation signal. We characterize the correlation strength via the degree of
squeezing of particle number-difference fluctuations in a certain
momentum-space volume and show that the correlation strength can be increased
if the signals are binned into larger counting volumes.
\\ ( http://arXiv.org/abs/cond-mat/0606345 , 310kb)
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Paper: cond-mat/0606353
Date: Wed, 14 Jun 2006 07:11:04 GMT (170kb)

Title: Generalized exclusion statistics and degenerate signature of strongly
interacting anyons
Authors: M T Batchelor and X W Guan
Subj-class: Statistical Mechanics; Strongly Correlated Electrons
\\
We show that below the degenerate temperature the distribution profiles of
strongly interacting anyons in one dimension coincide with the most probable
distributions of ideal particles obeying generalized exclusion statistics
(GES). The thermodynamics and the local two-particle correlation function
derived from the GES are in good agreement with the results derived for the
anyon model using the thermodynamic Bethe Ansatz. The anyonic interaction and
the dynamical interaction implement a continuous range of GES, providing a
signature of strongly interacting anyons, including the strongly interacting 1D
Bose gas.
\\ ( http://arXiv.org/abs/cond-mat/0606353 , 170kb)
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Paper: cond-mat/0606363
Date: Wed, 14 Jun 2006 09:44:21 GMT (19kb)

Title: Nonequivalent operator representations for Bose-condensed systems
Authors: V.I. Yukalov
Comments: Latex file, 27 pages, no figures
Subj-class: Statistical Mechanics
Journal-ref: Laser Phys. 16 (2006) 511-525
\\
The necessity of accurately taking into account the existence of
nonequivalent operator representations, associated with canonical
transformations, is discussed. It is demonstrated that Bose systems in the
presence of the Bose-Einstein condensate and without it correspond to different
Fock spaces, orthogonal to each other. A composite representation for the field
operators is constructed, allowing for a self-consistent description of
Bose-condensed systems. Equations of motion are derived from the given
Hamiltonian, which guarantees the validity of conservation laws and
thermodynamic self-consistency. At the same time, the particle spectrum,
obtained either from diagonalizing this Hamiltonian or from linearizing the
field-operator equations of motion, has no gap. The condition of the condensate
existence assures the absence of the gap in the spectrum, irrespectively to the
approximation involved. The suggested self-consistent theory is both conserving
and gapless.
\\ ( http://arXiv.org/abs/cond-mat/0606363 , 19kb)
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Paper: cond-mat/0606383
Date: Wed, 14 Jun 2006 19:35:42 GMT (22kb)

Title: Coherent impurity motion in a strongly correlated hard-core boson
quantum solid
Authors: Efstratios Manousakis
Comments: four two-column Revtex pages, 2 figures
Subj-class: Strongly Correlated Electrons; Statistical Mechanics
\\
A quantum lattice gas model is proposed to capture the essential aspects of
the motion of an impurity in a purely bosonic strongly correlated quantum solid
(such as a He-3 atom in solid He-4). Within the spin''-wave approximation the
model reduces to an effective Hamiltonian in which the impurity motion couples
linearly to bosonic excitations and in the non-crossing approximation we solve
the Dyson's equations for the impurity Green's functions for the square
lattice. We find that both substitutional and interstitial impurity
quasiparticles form sharp well-defined coherent low-energy excitations. We
discuss the possible relevance of our results to the superfluidity of solid
He-4.
\\ ( http://arXiv.org/abs/cond-mat/0606383 , 22kb)
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\\
Paper: cond-mat/0605184
replaced with revised version Wed, 14 Jun 2006 11:59:12 GMT (851kb)

Title: A Mott state of molecules
Authors: T. Volz, N. Syassen, D. M. Bauer, E. Hansis, S. D\"urr, G. Rempe
Subj-class: Statistical Mechanics
\\ ( http://arXiv.org/abs/cond-mat/0605184 , 851kb)
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\\
Paper: quant-ph/0606122
Date: Wed, 14 Jun 2006 15:37:20 GMT (37kb)

Title: Is the Fair Sampling Assumption supported by EPR Experiments?
Authors: Guillaume Adenier and Andrei Yu. Khrennikov
\\
We analyse optical EPR experimental data performed by Weihs et al in
Innsbruck 1997-1998. We show that for some linear combinations of the raw
coincidence rates, the experimental results display some anomalous behavior
that a more general source state (like non-maximally entangled state) cannot
straightforwardly account for. We attempt to explain these anomalies by taking
account of the relative efficiencies of the four channels. For this purpose, we
use the fair sampling assumption, and assume explicitly that the detection
efficiencies for the pairs of entangled photons can be written as a product of
the two corresponding detection efficiencies for the single photons. Although
the explicit use of the Fair Sampling assumption does reduce the magnitude of
observed anomalies, we show that is is however insufficient to remove them
completely.
\\ ( http://arXiv.org/abs/quant-ph/0606122 , 37kb)
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\\
Paper: physics/0606126
Date: Wed, 14 Jun 2006 16:48:02 GMT (224kb)

Title: Atom interferometry gravity-gradiometer for the determination of the
Newtonian gravitational constant G
Authors: A. Bertoldi, G. Lamporesi, L. Cacciapuoti, M. de Angelis, M. Fattori,
T. Petelski, A. Peters, M. prevedelli, J. Stuhler, G. M. Tino
Subj-class: Atomic Physics; General Physics
\\
We developed a gravity-gradiometer based on atom interferometry for the
determination of the Newtonian gravitational constant \textit{G}. The
apparatus, combining a Rb fountain, Raman interferometry and a juggling scheme
for fast launch of two atomic clouds, was specifically designed to reduce
possible systematic effects. We present instrument performances and show that
the sensor is able to detect the gravitational field induced by source masses.
A discussion of projected accuracy for \textit{G} measurement using this new
scheme shows that the results of the experiment will be significant to
discriminate between previous inconsistent values.
\\ ( http://arXiv.org/abs/physics/0606126 , 224kb)
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\\
Paper: cond-mat/0606398
Date: Thu, 15 Jun 2006 06:47:47 GMT (984kb)

Title: Landau damping: instability mechanism of superfluid Bose gases moving in
optical lattices
Authors: Kiyohito Iigaya, Satoru Konabe, Ippei Danshita, and Tetsuro Nikuni
Subj-class: Other
\\
We investigate Landau damping of Bogoliubov excitations in a dilute Bose gas
moving in an optical lattice at finite temperatures. Using a 1D tight-binding
model, we explicitly obtain the Landau damping rate, the sign of which
determines the stability of the condensate. We find that the sign changes at a
certain condensate velocity, which is exactly the same as the critical velocity
determined by the Landau criterion of superfluidity. This coincidence of the
critical velocities reveals the microscopic mechanism of the Landau
instability. This instability mechanism is also consistent with the recent
experiment suggesting that a thermal cloud plays a crucial role in breakdown of
superfluids, since the thermal cloud is also vital in the Landau damping
process. We also examine the possibility of simultaneous disappearance of all
damping processes.
\\ ( http://arXiv.org/abs/cond-mat/0606398 , 984kb)
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\\
Paper: cond-mat/0606409
Date: Thu, 15 Jun 2006 11:35:43 GMT (20kb)

Title: Ground State of a System of N Hard Core Quantum Particles in 1D Box
Authors: Yatendra S Jain
Subj-class: Soft Condensed Matter
\\
The ground state of a system of $N$ impenetrable hard core quantum particles
in a 1-D box is analyzed by using a new scheme applied recently to study a
similar system of two such particles {\it [Centl. Eur. J. Phys., 2(4), 709
(2004)]}. Accordingly, each particle of the system behaves like an independent
entity represented by a {\it macro-orbital}, -a kind of pair waveform identical
to that of a pair of particles moving with ($q$, $-q$) momenta at their {\it
center of mass} which may have any momentum $K$ in the laboratory frame. It
concludes: (i) $<A\delta{(x)}> = 0$, (ii) $<x> \ge \lambda/2$ and (iii) $q \ge q_o (= \pi/d)$ (with $d = L/N$ being the average nearest neighbour distance),
{\it etc.} While all bosons in their ground state have $q = q_o$ and $K = 0$,
fermions have $q= q_o$ with different $K$ ranging between 0 and $K = K_F$ (the
Fermi wave vector). Independent of their bosonic or fermionic nature, all
particles in the ground state define a close packed arrangement of their equal
size wave packets representing an ordered state in phase ($\phi-$)space with
$\Delta\phi = 2n\pi$ (with $n$ = 1,2,3, ...), $<x> = \lambda/2 = d$, and $q = q_o$. As such our approach uses greatly simplified mathematical formulation and
renders a visibly clear picture of the low energy states of the systems and its
results supplement earlier studies in providing their complete understanding.
\\ ( http://arXiv.org/abs/cond-mat/0606409 , 20kb)
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\\
Paper: cond-mat/0606416
Date: Thu, 15 Jun 2006 15:21:53 GMT (591kb)

Title: Mixing of ultracold atomic clouds by merging of two magnetic traps
Authors: Jesper Fevre Bertelsen, Henrik Kjaer Andersen, Sune Mai, and Michael
Budde
Subj-class: Other
\\
We demonstrate a new method to make mixtures of ultracold atoms which avoids
the two-species magneto-optical trap. We prepare two clouds of $^{87}$Rb atoms
in distinct magnetic quadrupole traps and mix the two clouds by merging the
traps. For correctly chosen parameters the mixing can be done essentially
without loss of atoms and with only minor heating. The basic features of the
process can be accounted for by a classical simulation of particle
trajectories. Such calculations indicate that mixing of different mass species
is also feasible, opening the way for using the method as a starting point for
making quantum gas mixtures.
\\ ( http://arXiv.org/abs/cond-mat/0606416 , 591kb)
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\\
Paper (*cross-listing*): math-ph/0606026
Date: Thu, 8 Jun 2006 13:06:10 GMT (18kb)

Title: The Functional Integration and the Two-Point Correlation Functions of
the Trapped Bose Gas
Authors: C. Malyshev, N. M. Bogoliubov
Comments: Extended version of the talk at The 8th International Conference
Path Integrals from Quantum Information to Cosmology'' (Prague, June 6-10,
2005)
Subj-class: Mathematical Physics; Statistical Mechanics; Exactly Solvable and
Integrable Systems
MSC-class: 81S40; 42C10
\\
A quantum field-theoretical model, which describes spatially non-homogeneous
repulsive Bose gas in an external harmonic potential is considered. Two-point
thermal correlation functions of the Bose gas are calculated in the framework
of the functional integration approach. Successive integration over the
high-energy'' functional variables first and then over the low-energy''
ones is used. The effective action functional for the low-energy variables is
obtained in one loop approximation. The functional integral representations for
the correlation functions are estimated by means of the stationary phase
approximation. A power-law asymptotical behaviour of the correlators of the
one-dimensional Bose gas is demonstrated in the limit, when the temperature is
going to zero, while the volume occupied by the non-homogeneous Bose gas
infinitely increases. The power-law behaviour is governed by the critical
exponent dependent on the spatial arguments.
\\ ( http://arXiv.org/abs/math-ph/0606026 , 18kb)
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\\
Paper (*cross-listing*): hep-th/0510238
replaced with revised version Thu, 15 Jun 2006 19:11:15 GMT (10kb)

Title: Casimir forces in Bose-Einstein condensates: finite size effects in
three-dimensional rectangular cavities
Authors: Ariel Edery
Comments: 12 pages; no figures; v.2: version accepted for publication in JSTAT
Subj-class: High Energy Physics - Theory; Statistical Mechanics
Journal-ref: J. Stat. Mech. (2006) P06007
DOI: 10.1088/1742-5468/2006/06/P06007
\\ ( http://arXiv.org/abs/hep-th/0510238 , 10kb)
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\\
Paper: quant-ph/0606128
Date: Thu, 15 Jun 2006 02:20:53 GMT (230kb)

Title: How to observe a coherent superposition of an atom and a molecule
Authors: Mark R. Dowling, Stephen D. Bartlett, Terry Rudolph, and Robert W.
Spekkens
\\
We demonstrate that it is possible, in principle, to perform a Ramsey-type
interference experiment to exhibit a coherent superposition of a single atom
and a diatomic molecule. This gedanken experiment, based on the techniques of
Aharonov and Susskind [Phys. Rev. 155, 1428 (1967)], explicitly violates the
commonly-accepted superselection rule that forbids coherent superpositions of
eigenstates of differing atom number. This interference experiment makes use of
a Bose-Einstein condensate as a reference frame with which to perform the
coherent operations analogous to Ramsey pulses. We also investigate an
analogous gedanken experiment to exhibit a coherent superposition of a single
boson and a fermion, violating the commonly-accepted superselection rule
forbidding coherent superpositions of states of differing particle statistics;
in this case, the reference frame is realized by a multi-mode state of many
fermions. This latter case reproduces all of the relevant features of Ramsey
interferometry, including Ramsey fringes over many repetitions of the
experiment. However, the apparent inability of this proposed experiment to
produce well-defined relative phases between two distinct systems each
described by a coherent superposition of a boson and a fermion demonstrates
that there are additional, outstanding requirements to fully lift'' the
univalence superselection rule.
\\ ( http://arXiv.org/abs/quant-ph/0606128 , 230kb)
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\\
Paper: cond-mat/0606430
Date: Thu, 15 Jun 2006 21:22:01 GMT (741kb)

Title: Continuous and Pulsed Quantum Zeno Effect
Authors: Erik W. Streed, Jongchul Mun, Micah Boyd, Gretchen K. Campbell,
Patrick Medley, Wolfgang Ketterle, David E. Pritchard
Subj-class: Other
\\
Continuous and pulsed quantum Zeno effects were observed using a $^{87}$Rb
Bose-Einstein condensate(BEC). Oscillations between two ground hyperfine states
of a magnetically trapped condensate, externally driven at a transition rate
$\omega_R$, were suppressed by destructively measuring the population in one of
the states with resonant light. The suppression of the transition rate in the
two level system was quantified for pulsed measurements with a time interval
$\delta t$ between pulses and continuous measurements with a scattering rate
$\gamma$. We observe that the continuous measurements exhibit the same
suppression in the transition rate as the pulsed measurements when
$\gamma\delta t=3.60(0.43)$, in agreement with the predicted value of 4.
Increasing the measurement rate suppressed the transition rate down to
$0.005\omega_R$.
\\ ( http://arXiv.org/abs/cond-mat/0606430 , 741kb)
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\\
Paper: cond-mat/0606432
Date: Fri, 16 Jun 2006 00:39:20 GMT (694kb)

Title: Observation of Phase Separation in a Strongly-Interacting Imbalanced
Fermi Gas
Authors: Y. Shin, M. W. Zwierlein, C. H. Schunck, A. Schirotzek, W. Ketterle
Subj-class: Statistical Mechanics
\\
We have observed phase separation between the superfluid and the normal
component in a strongly interacting Fermi gas with imbalanced spin populations.
The in situ distribution of the density difference between two trapped spin
components is obtained using phase-contrast imaging and 3D image
reconstruction. A shell structure is clearly identified where the superfluid
region of equal densities is surrounded by a normal gas of unequal densities.
The phase transition induces a dramatic change in the density profiles as
excess fermions are expelled from the superfluid.
\\ ( http://arXiv.org/abs/cond-mat/0606432 , 694kb)
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\\
Paper: cond-mat/0601432
replaced with revised version Thu, 15 Jun 2006 21:38:02 GMT (439kb)

Title: Atomic matter of non-zero momentum Bose-Einstein condensation and
orbital current order
Authors: W. Vincent Liu and Congjun Wu
Comments: 10 pages, 7 figures (with one in Appendix); added references and
reorganized appendices in REVTeX
Subj-class: Other; Strongly Correlated Electrons
\\ ( http://arXiv.org/abs/cond-mat/0601432 , 439kb)
------------------------------------------------------------------------------

Till next week,
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/
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Received on Tue Jun 20 2006 - 09:17:38 EST

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