# Matt's arXiv selection, Monday 20th March 2006.

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Mon, 20 Mar 2006 10:24:50 +1000 (EST)

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Matt.

--
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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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Paper: cond-mat/0603273
Date: Fri, 10 Mar 2006 14:54:21 GMT   (55kb)
Title: Ultracold atomic F=2 spinor gas in an optical lattice
Authors: L. Zawitkowski, K. Eckert, A. Sanpera, M.Lewenstein
Subj-class: Other
\\
We investigate magnetic properties of Mott-insulating phases of ultracold F=2
spinor gases in optical lattices. We derive effective spin Hamiltonians for one
and two atoms per site and discuss the possibilities of manipulating the
magnetic properties of the system using Feshbach resonances. We discuss low
temperature quantum phases for 87Rb and 85Rb.
\\ ( http://arXiv.org/abs/cond-mat/0603273 ,  55kb)
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Paper: cond-mat/0603279
Date: Fri, 10 Mar 2006 01:05:34 GMT   (975kb)
Title: A Hybrid Apparatus for BEC and Cavity QED: Single Atom Detection in
Quantum Degenerate Gases
Authors: Anton \"{O}ttl, Stephan Ritter, Michael K\"ohl and Tilman Esslinger
Comments: A version with improved figure quality can be found at
http://www.quantumoptics.ethz.ch
Subj-class: Other
\\
We present and characterize an experimental system in which we achieve the
integration of an ultra-high finesse optical cavity with a Bose-Einstein
condensate (BEC). The conceptually novel design of the apparatus for the
production of BECs features nested vacuum chambers and an in-vacuo magnetic
transport configuration. It grants large scale spatial access to the BEC for
samples and probes via a modular and exchangeable "science platform". We are
able to produce \87Rb condensates of five million atoms and to output couple
continuous atom lasers. The cavity is mounted on the science platform on top of
a vibration isolation system. The optical cavity works in the strong coupling
regime of cavity quantum electrodynamics (QED) and serves as a quantum optical
detector for single atoms. This system enables us to study atom optics on a
single particle level and to further develop the field of quantum atom optics.
We describe the technological modules and the operation of the combined BEC
cavity apparatus. Its performance is characterized by single atom detection
measurements for thermal and quantum degenerate atomic beams. The atom laser
provides a fast and controllable supply of atoms coupling with the cavity mode
and allows for an efficient study of atom field interactions in the strong
coupling regime. Moreover, the high detection efficiency for quantum degenerate
atoms distinguishes the cavity as a sensitive and weakly invasive probe for
cold atomic clouds.
\\ ( http://arXiv.org/abs/cond-mat/0603279 ,  975kb)
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Paper: cond-mat/0603284
Date: Fri, 10 Mar 2006 07:55:34 GMT   (404kb)
Title: Modified Sagnac interferometer for high-sensitivity magneto-optic
measurements atcryogenic temperatures
Authors: Jing Xia, Peter T. Beyersdorf, Martin M. Fejer, and Aharon Kapitulnik
Subj-class: Other
\\
We describe a geometry for a Sagnac interferometer with a zero-area Sagnac
loop for measuring magneto-optic Kerr effect (MOKE) at cryogenic temperatures.
The apparatus is capable of measuring absolute polar Kerr rotation at 1550 nm
wavelength without any modulation of the magnetic state of the sample, and is
intrinsically immune to reciprocal effects such as linear birefringence and
thermal fluctuation. A single strand of polarization-maintaining (PM) fiber is
fed into a liquid helium probe, eliminating the need for optical viewports.
This configuration makes it possible to conduct MOKE measurements at much lower
temperatures than before. With an optical power of only 10 $\mu$W, we
demonstrate static Kerr measurements with a shot-noise limited sensitivity of
$1\times 10^{-7}$ rad/$\sqrt{\rm Hz}$ from room temperature down to 2K. Typical
bias drift was measured to be $3\times 10^{-7}$ rad/hour.
\\ ( http://arXiv.org/abs/cond-mat/0603284 ,  404kb)
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Paper: cond-mat/0603289
Date: Fri, 10 Mar 2006 13:07:35 GMT   (10kb)
Title: The difference of boundary effects between Bose and Fermi systems
Authors: Hai Pang, Wu-Sheng Dai, Mi Xie
Subj-class: Statistical Mechanics
Journal-ref: J. Phys. A: Math. Gen. 39 (2006) 2563-2571
\\
In this paper, we show that there exists an essential difference of boundary
effects between Bose and Fermi systems both for Dirichlet and Neumann boundary
conditions: at low temperatures and high densities the influence of the
boundary on the Bose system depends on the temperature but is independent of
the density, but for the Fermi case the influence of the boundary is
independent of the temperature but depends on the density, after omitting the
negligible high-order corrections. We also show that at high temperatures and
low densities the difference of the influence of the boundary between Bose and
Fermi systems appears in the next-to-leading order boundary contribution, and
the leading boundary contribution is independent of the density. Moreover, for
calculating the boundary effects at high temperatures and low densities, since
the existence of the boundary modification causes the standard virial expansion
to be invalid, we introduce a modified virial expansion.
\\ ( http://arXiv.org/abs/cond-mat/0603289 ,  10kb)
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Paper: cond-mat/0603299
Date: Fri, 10 Mar 2006 18:08:43 GMT   (26kb)
Title: Fermions in optical lattices near a Feshbach resonance: from band
insulator to Mott insulator
Authors: A. F. Ho
Comments: 4 pages, 2 .eps files
Subj-class: Mesoscopic Systems and Quantum Hall Effect; Strongly Correlated
Electrons
\\
We study a model of an equal mixture of two species of fermions in a deep
optical lattice at a filling of two fermions per site. At weak inter-species
interaction, the system is a band insulator. When the inter-species interaction
is tuned via a Feshbach resonance to be larger than an energy related to the
energy separation of the first and second Bloch band, atoms populate equally
the two Bloch bands. With weak tunneling between sites of the optical lattice,
the system becomes a Mott insulator with the low energy effective Hamiltonian
of a spin-1 Heisenberg antiferromagnet, because of a Hund's rule like coupling
between the two bands. We discuss experimental signatures of these two types of
insulators.
\\ ( http://arXiv.org/abs/cond-mat/0603299 ,  26kb)
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Paper: cond-mat/0601122
replaced with revised version Fri, 10 Mar 2006 10:22:37 GMT   (38kb)
Title: Density profile of a polarized unitary Fermi gas
Authors: Fr\'{e}d\'{e}ric Chevy (LKB - Lhomond)
Proxy: ccsd ccsd-00016604
Subj-class: Statistical Mechanics
\\ ( http://arXiv.org/abs/cond-mat/0601122 ,  38kb)
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Paper: quant-ph/0603090
Date: Fri, 10 Mar 2006 12:07:44 GMT   (39kb)
Title: Finite-dimensional states and entanglement generation for a nonlinear
coupler
Authors: A. Kowalewska-Kud{\l}aszyk, W. Leo\'nski
Comments: Accepted for publication in Physical Review A
\\
We discuss a system comprising two nonlinear (Kerr-like) oscillators coupled
mutually by a nonlinear interaction. The system is excited by an external
coherent field that is resonant to the frequency of one of the oscillators. We
show that the coupler evolution can be closed within a finite set of $n$-photon
states, analogously as in the \textit{nonlinear quantum scissors} model.
Moreover, for this type of evolution our system can be treated as a
\textit{Bell-like states} generator. Thanks to the nonlinear nature of both:
oscillators and their internal coupling, these states can be generated even if
the system exhibits its energy dissipating nature, contrary to systems with
linear couplings.
\\ ( http://arXiv.org/abs/quant-ph/0603090 ,  39kb)
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Paper: quant-ph/0603093
Date: Fri, 10 Mar 2006 13:14:40 GMT   (678kb)
Title: Bloch-Zener oscillations
Authors: B. M. Breid, D. Witthaut, and H. J. Korsch
\\
It is well known that a particle in a periodic potential with an additional
constant force performs Bloch oscillations. Modulating every second period of
the potential, the original Bloch band splits into two subbands. The dynamics
of quantum particles shows a coherent superposition of Bloch oscillations and
Zener tunneling between the subbands, a Bloch-Zener oscillation. Such a system
is modelled by a tight-binding Hamiltonian, a system of two minibands with an
easily controllable gap. The dynamics of the system is investigated by using an
algebraic ansatz leading to a differential equation of Whittaker-Hill type. It
is shown that the parameters of the system can be tuned to generate a periodic
reconstruction of the wave packet and thus of the occupation probability. As an
application, the construction of a matter wave beam splitter and a Mach-Zehnder
interferometer is briefly discussed.
\\ ( http://arXiv.org/abs/quant-ph/0603093 ,  678kb)
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Paper: quant-ph/0603095
Date: Fri, 10 Mar 2006 14:26:04 GMT   (22kb)
Title: Saturation of fidelity in the atom-optics kicked rotor
Authors: Sandro Wimberger and Andreas Buchleitner
Journal-ref: J. Phys. B: At. Mol. Opt. Phys. 39, L145-L151 (2006)
DOI: 10.1088/0953-4075/39/7/L01
\\
We show that the quantum fidelity is accessible to cold atom experiments for
a large class of evolutions in periodical potentials, properly taking into
account the experimental initial conditions of the atomic ensemble. We prove
analytically that, at the fundamental quantum resonances of the atom-optics
kicked rotor, the fidelity saturates at a constant, time-independent value
after a small number of kicks. The latter saturation arises from the bulk of
the atomic ensemble, whilst for the resonantly accelerated atoms the fidelity
is predicted to decay slowly according to a power law.
\\ ( http://arXiv.org/abs/quant-ph/0603095 ,  22kb)
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Paper: cond-mat/0603317
Date: Mon, 13 Mar 2006 17:11:30 GMT   (40kb)
Title: Synchronization in the BCS Pairing Dynamics as a Critical Phenomenon
Authors: R. A. Barankov and L. S. Levitov
Subj-class: Mesoscopic Systems and Quantum Hall Effect; Superconductivity
\\
Fermi gas with time-dependent pairing interaction hosts several different
dynamical states. Coupling between the collective BCS pairing mode and
individual Cooper pair states can make the latter either synchronize or
dephase. We describe transition from phase-locked undamped oscillations to
Landau-damped dephased oscillations in the collisionless, dissipationless
regime as a function of coupling strength. In the dephased regime, we find a
second transition at which the long-time asymptotic pairing amplitude vanishes.
Using a combination of numerical and analytical methods we establish a
continuous (type II) character of both transitions.
\\ ( http://arXiv.org/abs/cond-mat/0603317 ,  40kb)
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Paper: cond-mat/0603319
Date: Sun, 12 Mar 2006 11:43:55 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
\\
We report results of quantum Monte Carlo simulations in the canonical and the
grand-canonical ensemble of the two- and three-dimensional Bose-Hubbard model
with quadratic and quartic confining potentials. The quantum criticality of the
superfluid-Mott insulator transition is investigated both on the boundary layer
separating the two coexisting phases and at the center of the traps where the
Mott-insulating phase is first established. Recent simulations of systems in
quadratic traps have shown that the transition is not in the critical regime
due to the finite gradient of the confining potential and that critical
fluctuations are suppressed. In addition, it has been shown that quantum
critical behavior is recovered in flat confining potentials as they approach
the uniform regime. Our results show that quartic traps display a behavior
similar to quadratic ones, yet locally at the center of the traps the bulk
transition has enhanced critical fluctuations in comparison to the quadratic
case. Therefore quartic traps provide a better prerequisite for the
experimental observation of true quantum criticality of ultracold bosonic atoms
in optical lattices.
\\ ( http://arXiv.org/abs/cond-mat/0603319 ,  301kb)
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Paper: cond-mat/0603332
Date: Mon, 13 Mar 2006 03:52:33 GMT   (411kb)
Title: Mean field phase diagrams of imbalanced Fermi gases near a Feshbach
resonance
Authors: Hui Hu and Xia-Ji Liu
Comments: 4 pages + 5 figures
Subj-class: Strongly Correlated Electrons; Superconductivity
\\
We propose phase diagrams for an imbalanced (unequal number of atoms or Fermi
surface in two pairing hyperfine states) gas of atomic fermions near a broad
Feshbach resonance using mean field theory. Particularly, in the plane of
interaction and polarization we determine the region for a mixed phase composed
of normal and superfluid components. We compare our prediction of phase
boundaries with the recent measurment, and find a good qualitative agreement.
\\ ( http://arXiv.org/abs/cond-mat/0603332 ,  411kb)
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Paper: cond-mat/0603334
Date: Mon, 13 Mar 2006 14:51:15 GMT   (29kb)
Title: Phases of Bosons or Fermions in confined optical lattices
Authors: H. Heiselberg
Subj-class: Superconductivity
\\
Phases of Bose or Fermi atoms in optical lattices confined in harmonic traps
are studied within the Thomas-Fermi approximation. Critical radii and particle
number for onset of Mott insulator states are calculated and phase diagrams
shown in 1D, and estimated for 2 and 3D. Methods to observe these and novel
phases such as d-wave superconductivity is discussed. Specifically the
collective modes are calculated.
\\ ( http://arXiv.org/abs/cond-mat/0603334 ,  29kb)
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Paper: cond-mat/0603340
Date: Mon, 13 Mar 2006 10:13:46 GMT   (19kb)
Title: Calogero-Sutherland gas of ultracold Bose atoms
Authors: Yue Yu
Subj-class: Other; Statistical Mechanics
\\
We show that a famous exact soluble one-dimensional system, the
Calogero-Sutherland gas with an inverse square long range interaction, can be
realized in a cold Bose atom system with a dipole-dipole interaction by
dimension reduction. The low-lying excitations are a Luttinger liquid that can
be characterized by its exclusion statistics parameter. We hope the ground
state and low-lying excitation behaviors may be observed in the time of flight
experiment.
\\ ( http://arXiv.org/abs/cond-mat/0603340 ,  19kb)
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Paper: cond-mat/0505657
replaced with revised version Mon, 13 Mar 2006 09:58:39 GMT   (442kb)
Title: Renormalization group approach to the spin-1 Bose gas
Authors: Gergely Szirmai
Comments: 7 pages, 5 figures included in text, final version, journal reference
Subj-class: Statistical Mechanics
Journal-ref: Eur. Phys. J. D 37, 427-433 (2006)
\\ ( http://arXiv.org/abs/cond-mat/0505657 ,  442kb)
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Paper: cond-mat/0509274
replaced with revised version Mon, 13 Mar 2006 05:33:29 GMT   (171kb)
Title: Temperature of a trapped unitary Fermi gas at finite entropy
Authors: Hui Hu, Xia-Ji Liu, and Peter D. Drummond
Comments: 5 pages, and 4 figures; Published version in Phys. Rev. A
Subj-class: Superconductivity; Statistical Mechanics
Journal-ref: Phys. Rev. A 73, 023617 (2006)
DOI: 10.1103/PhysRevA.73.023617
\\ ( http://arXiv.org/abs/cond-mat/0509274 ,  171kb)
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Paper: cond-mat/0511052
replaced with revised version Sun, 12 Mar 2006 09:41:41 GMT   (227kb)
Title: Einstein--de Haas Effect in Dipolar Bose-Einstein Condensates
Authors: Yuki Kawaguchi, Hiroki Saito, and Masahito Ueda
Comments: 4 pages, 4 figures; Final version
Subj-class: Other
Journal-ref: Phys. Rev. Lett. 96, 080405 (2006)
DOI: 10.1103/PhysRevLett.96.080405
\\ ( http://arXiv.org/abs/cond-mat/0511052 ,  227kb)
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Paper: cond-mat/0603190
replaced with revised version Mon, 13 Mar 2006 18:07:44 GMT   (18kb)
Title: Realization, Characterization, and Detection of Novel Superfluid Phases
with Pairing between Unbalanced Fermion Species
Authors: Kun Yang
Comments: This is an invited contribution to a book titled "Pairing beyond BCS
Theory in Fermionic Systems" (Mark Alford, John Clark and Armen Sedrakian,
Subj-class: Superconductivity
\\ ( http://arXiv.org/abs/cond-mat/0603190 ,  18kb)
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Paper: physics/0603093
Date: Sun, 12 Mar 2006 19:22:33 GMT   (14kb)
Title: Regime of Validity of the Pairing Hamiltonian in the Study of Fermi
Gases
Authors: S. Y. Chang, V. R. Pandharipande
Subj-class: Atomic Physics
\\
The ground state energy and pairing gap of the interacting Fermi gases
calculated by the {\it ab initio} stochastic method are compared with those
estimated from the Bardeen-Cooper-Schrieffer pairing Hamiltonian. We discuss
the ingredients of this Hamiltonian in various regimes of interaction strength.
In the weakly interacting ($1/ak_F <<0$) regime the BCS Hamiltonian should
describe Landau quasi-particle energies and interactions, on the other hand in
the strongly pairing regime, that is $1/ak_F \gtrsim 0$, it becomes part of the
bare Hamiltonian. However, the bare BCS Hamiltonian is not adequate for
describing atomic gases in the regime of weak to moderate interaction strength
$-\infty < 1/ak_F <0$ such as $ak_F \sim -1$.
PACS: 05.30.Fk, 03.75.Ss, 21.65.+f
\\ ( http://arXiv.org/abs/physics/0603093 ,  14kb)
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Paper: cond-mat/0603362
Date: Tue, 14 Mar 2006 10:48:57 GMT   (110kb)
Title: Quantum resonance and anti-resonance for a periodically kicked
Bose-Einstein Condensate in a one dimensional Box
Authors: Dario Poletti, Libin Fu, Jie Liu, and Baowen Li
Subj-class: Mesoscopic Systems and Quantum Hall Effect
\\
We investigate the quantum dynamics of a periodically kicked Bose-Einstein
Condensate confined in a one dimensional (1D) Box both numerically and
theoretically, emphasizing on the phenomena of quantum resonance and
anti-resonance. The quantum resonant behavior of BEC is different from the
single particle case but the anti-resonance condition ($T = 2\pi$ and $\alpha = 0$) is not affected by the atomic interaction. For the anti-resonance case, the
nonlinearity (atom interaction) causes the transition between oscillation and
quantum beating. For the quantum resonance case, because of the coherence of
BEC, the energy increase is oscillating and the rate is dramatically affected
by the many-body interaction. We also discuss the relation between the quantum
resonant behavior and the KAM or non-KAM property of the corresponding
classical system.
\\ ( http://arXiv.org/abs/cond-mat/0603362 ,  110kb)
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Paper: cond-mat/0603384
Date: Tue, 14 Mar 2006 17:32:23 GMT   (103kb)
Title: Expansion of a Fermi Cloud in the BCS-BEC Crossover
Authors: Giovanni Diana, Nicola Manini, Luca Salasnich
Subj-class: Statistical Mechanics
\\
We study the free expansion of a dilute two-component Fermi gas with
attractive interspecies interaction in the BCS-BEC crossover. We apply a
time-dependent parameter-free density-functional theory by using two choices of
the equation of state: an analytic formula based on Monte Carlo data and the
mean-field equation of state resulting from the extended BCS equations. The
calculated axial and transverse radii and the aspect ratio of the expanding
cloud are compared to experimental data on vapors of ^6Li atoms. Remarkably,
the mean-field theory shows a better agreement with the experiments than the
theory based on the Monte Carlo equation of state. Both theories predict a
measurable dependence of the aspect ratio on expansion time and on scattering
length.
\\ ( http://arXiv.org/abs/cond-mat/0603384 ,  103kb)
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Paper: cond-mat/0603389
Date: Tue, 14 Mar 2006 19:24:44 GMT   (979kb)
Title: On Dispersive and Classical Shock Waves in Bose-Einstein Condensates and
Gas Dynamics
Authors: M. A. Hoefer, M. J. Ablowitz, I. Coddington, E. A. Cornell, P. Engels,
and V. Schweikhard
Comments: 24 pages, 28 figures, submitted to Phys Rev A
Subj-class: Other
\\
A Bose-Einstein condensate (BEC) is a quantum fluid that gives rise to
interesting shock wave nonlinear dynamics. Experiments depict a BEC that
exhibits behavior similar to that of a shock wave in a compressible gas, eg.
traveling fronts with steep gradients. However, the governing Gross-Pitaevskii
(GP) equation that describes the mean field of a BEC admits no dissipation
hence classical dissipative shock solutions do not explain the phenomena.
Instead, wave dynamics with small dispersion is considered and it is shown that
this provides a mechanism for the generation of a dispersive shock wave (DSW).
Computations with the GP equation are compared to experiment with excellent
agreement. A comparison between a canonical 1D dissipative and dispersive shock
problem shows significant differences in shock structure and shock front speed.
Numerical results associated with the three dimensional experiment show that
three and two dimensional approximations are in excellent agreement and one
dimensional approximations are in good qualitative agreement. Using one
dimensional DSW theory it is argued that the experimentally observed blast
waves may be viewed as dispersive shock waves.
\\ ( http://arXiv.org/abs/cond-mat/0603389 ,  979kb)
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Paper: cond-mat/0511746
replaced with revised version Tue, 14 Mar 2006 16:52:32 GMT   (352kb)
Title: Strongly correlated Fermi-Bose mixtures in disordered optical lattices
Authors: L. Sanchez-Palencia (LCFIO), V. Ahufinger, A. Kantian, Jakub
Zakrzewski, A. Sanpera, M. Lewenstein
Comments: Proceedings of the 3rd International Workshop on `Theory of Quantum
Gases and Quantum Coherence'
Proxy: ccsd ccsd-00014953
Subj-class: Other
\\ ( http://arXiv.org/abs/cond-mat/0511746 ,  352kb)
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Paper: quant-ph/0508010
replaced with revised version Mon, 13 Mar 2006 21:16:35 GMT   (145kb)
Title: Measurement of the separation between atoms beyond diffraction limit
Authors: Jun-Tao Chang, Joerg Evers, Marlan O. Scully, and M. Suhail Zubairy
Comments: v2: Revised version for publication
Journal-ref: Phys. Rev. A 73, 031803(R) (2006)
DOI: 10.1103/PhysRevA.73.031803
\\ ( http://arXiv.org/abs/quant-ph/0508010 ,  145kb)
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Paper: physics/0603107
Date: Mon, 13 Mar 2006 22:19:26 GMT   (533kb)
Title: Ultracold Atoms Driven by a Kicked Rotor in a Finite Box
Authors: K. Henderson, H. Kelkar, T.C. Li, B. Gutierrez-Medina and M.G. Raizen
Subj-class: Atomic Physics
\\
We study the effect of different heating rates of a dilute Bose gas confined
in a quasi-1D finite, leaky box. An optical kicked-rotor is used to transfer
energy to the atoms while two repulsive optical beams are used to confine the
atoms. The average energy of the atoms is localized after a large number of
kicks and the system reaches a nonequilibrium steady state. A numerical
simulation of the experimental data suggests that the localization is due to
energetic atoms leaking over the barrier. Our data also indicates a correlation
between collisions and the destruction of the Bose-Einstein condensate
fraction.
\\ ( http://arXiv.org/abs/physics/0603107 ,  533kb)
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Paper: physics/0602011
replaced with revised version Tue, 14 Mar 2006 19:46:54 GMT   (109kb)
Title: Demonstration of a Cold Atom Fountain Electron Electric Dipole Moment
Experiment
Authors: Jason M. Amini, Charles T. Munger Jr., Harvey Gould
Comments: 4 pages, 4 figures, references to neutrino flavor added and grammar
corrected
Subj-class: Atomic Physics
\\ ( http://arXiv.org/abs/physics/0602011 ,  109kb)
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Paper: cond-mat/0603402
Date: Wed, 15 Mar 2006 10:06:58 GMT   (20kb)
Title: Monte Carlo simulation of boson lattices
Authors: Vesa Apaja and Olav F. Syljuasen
Subj-class: Statistical Mechanics
\\
Boson lattices are theoretically well described by the Hubbard model. The
basic model and its variants can be effectively simulated using Monte Carlo
techniques. We describe two newly developed approaches, the Stochastic Series
Expansion (SSE) with directed loop updates and continuous--time Diffusion Monte
Carlo (CTDMC). SSE is a formulation of the finite temperature partition
function as a stochastic sampling over product terms. Directed loops is a
general framework to implement this stochastic sampling in a non--local fashion
while maintaining detailed balance. CTDMC is well suited to finding exact
ground--state properties, applicable to any lattice model not suffering from
the sign problem; for a lattice model the evolution of the wave function can be
performed in continuous time without any time discretization error. Both the
directed loop algorithm and the CTDMC are important recent advances in
development of computational methods. Here we present results for a Hubbard
model for anti--ferromagnetic spin--1 bosons in one dimensions, and show
evidence for a dimerized ground state in the lowest Mott lobe.
\\ ( http://arXiv.org/abs/cond-mat/0603402 ,  20kb)
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Paper: cond-mat/0603404
Date: Wed, 15 Mar 2006 16:57:37 GMT   (136kb)
Title: Dynamical vanishing of the order parameter in a fermionic condensate
Authors: Emil A. Yuzbashyan and Maxim Dzero
Subj-class: Superconductivity; Other
\\
We analyze the dynamics of a condensate of an ultra-cold atomic fermions
following an abrupt change of the pairing strength. At long times, the system
goes to a non-stationary steady state. The superfluid order parameter
asymptotes to a constant value, which we determine exactly. We show that the
order parameter vanishes dynamically when the pairing strength is decreased
below a certain critical value. In this case, the steady state of the system
combines properties of normal and superfluid states - the spectroscopic gap and
the condensate fraction vanish, while the superfluid density is nonzero.
\\ ( http://arXiv.org/abs/cond-mat/0603404 ,  136kb)
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Paper: quant-ph/0603138
Date: Wed, 15 Mar 2006 15:59:49 GMT   (164kb)
Title: Theoretical analysis of the implementation of a quantum phase gate with
neutral atoms on atom chips
Authors: E. Charron, M. A. Cirone, A. Negretti, J. Schmiedmayer, T. Calarco
Comments: 9 pages, 5 color figures
\\
We present a detailed, realistic analysis of the implementation of a proposal
for a quantum phase gate based on atomic vibrational states, specializing it to
neutral rubidium atoms on atom chips. We show how to create a double--well
potential with static currents on the atom chips, using for all relevant
parameters values that are achieved with present technology. The potential
barrier between the two wells can be modified by varying the currents in order
to realize a quantum phase gate for qubit states encoded in the atomic external
degree of freedom. The gate performance is analyzed through numerical
simulations; the operation time is ~10 ms with a performance fidelity above
99.9%. For storage of the state between the operations the qubit state can be
transferred efficiently via Raman transitions to two hyperfine states, where
its decoherence is strongly inhibited. In addition we discuss the limits
imposed by the proximity of the surface to the gate fidelity.
\\ ( http://arXiv.org/abs/quant-ph/0603138 ,  164kb)
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Paper: cond-mat/0603424
Date: Thu, 16 Mar 2006 04:45:22 GMT   (267kb)
Title: Superfluid Dynamics of a Bose-Einstein Condensate in an Optical
Super-Lattice
Authors: Aranya B Bhattacherjee
Subj-class: Statistical Mechanics
\\
We derive and study the Bogoliubov-Bloch spectrum of a Bose-Einstein
condensate (BEC) confined in a one-dimensional optical superlattice, using the
Bogoliubov approximation and the hydrodynamic theory. We show that a BEC in an
optical superlattice experiences atleast two different tunneling parameter and
hence behaves like a chain of diatomic lattice. This gives rise to a gapped
branch in addition to the gapless acoustical branch in the Bogoliubov-Bloch
spectrum. The spectrum strongly depends on the strength of the secondary
lattice, the interaction parameter and the number density of atoms.
\\ ( http://arXiv.org/abs/cond-mat/0603424 ,  267kb)
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Paper: cond-mat/0511684
replaced with revised version Thu, 16 Mar 2006 01:36:44 GMT   (745kb)
Title: Critical fluctuations in a soliton formation of attractive Bose-Einstein
condensates
Authors: Rina Kanamoto, Hiroki Saito, Masahito Ueda
Subj-class: Other
Journal-ref: Phys. Rev. A 73, 033611 (2006)
\\ ( http://arXiv.org/abs/cond-mat/0511684 ,  745kb)
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Paper: cond-mat/0601147
replaced with revised version Thu, 16 Mar 2006 10:44:43 GMT   (888kb)
Title: LOFF Pairing vs. Breached Pairing in Asymmetric Fermion Superfluids
Authors: Lianyi He, Meng Jin and Pengfei Zhuang
Subj-class: Superconductivity
\\ ( http://arXiv.org/abs/cond-mat/0601147 ,  888kb)
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Paper: quant-ph/0603147
Date: Thu, 16 Mar 2006 16:10:22 GMT   (27kb)
Title: Test of the quantumness of atom-atom correlations in a bosonic gas
Authors: D. Ivanov and S. Wallentowitz
Journal-ref: Europhys. Lett. 73, 499 (2006)
DOI: 10.1209/epl/i2005-10435-1
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It is shown how the quantumness of atom-atom correlations in a trapped
bosonic gas can be made observable. Application of continuous feedback control
of the center of mass of the atomic cloud is shown to generate oscillations of
the spatial extension of the cloud, whose amplitude can be directly used as a
characterization of atom-atom correlations. Feedback parameters can be chosen
such that the violation of a Schwarz inequality for atom-atom correlations can
be tested at noise levels much higher than the standard quantum limit.
\\ ( http://arXiv.org/abs/quant-ph/0603147 ,  27kb)
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Paper: physics/0603127
Date: Wed, 15 Mar 2006 22:38:58 GMT   (264kb)
Title: Focusing a fountain of neutral cesium atoms with an electrostatic lens
triplet
Authors: Juris G. Kalnins, Jason M. Amini, Harvey Gould
Report-no: LBNL-57137
Subj-class: Accelerator Physics; Atomic Physics
Journal-ref: Phys. Rev. A72, 043406 (2005)
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An electrostatic lens with three focusing elements in an alternating-gradient
configuration is used to focus a fountain of cesium atoms in their ground
(strong-field-seeking) state. The lens electrodes are shaped to produce only
sextupole plus dipole equipotentials which avoids adding the unnecessary
nonlinear forces present in cylindrical lenses. Defocusing between lenses is
greatly reduced by having all of the main electric fields point in the same
direction and be of nearly equal magnitude. The addition of the third lens gave
us better control of the focusing strength in the two transverse planes and
allowed focusing of the beam to half the image size in both planes. The beam
envelope was calculated for lens voltages selected to produced specific
focusing properties. The calculations, starting from first principles, were
compared with measured beam sizes and found to be in good agreement.
Application to fountain experiments, atomic clocks, and focusing polar
molecules in strong-field-seeking states is discussed.
\\ ( http://arXiv.org/abs/physics/0603127 ,  264kb)
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Received on Mon Mar 20 2006 - 10:24:50 EST

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