The following message was sent to the matts_arxiv list by Matthew Davis <mdavis_at_physics.uq.edu.au>
Hi all,
There were 33 new preprints and 11 replacements for this week.
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arXiv:0709.2187
Date: Thu, 13 Sep 2007 23:50:18 GMT (311kb)
Title: Manipulating atoms in an optical lattice: Fractional fermion number and
its optical quantum measurement
Authors: J. Ruostekoski, J. Javanainen, G. V. Dunne
Categories: cond-mat.other cond-mat.str-el
Comments: 18 pages, 9 figures
\\
We provide a detailed analysis of our previously proposed scheme [Phys. Rev.
Lett. 88, 180401, (2002)] to engineer the profile of the hopping amplitudes for
atomic gases in a 1D optical lattice so that the particle number becomes
fractional. We consider a constructed system of a dilute two-species gas of
fermionic atoms where the two components are coupled via a coherent
electromagnetic field with a topologically nontrivial phase profile. We show
both analytically and numerically how the resulting atomic Hamiltonian in a
prepared dimerized optical lattice with a defect in the pattern of alternating
hopping amplitudes exhibits a fractional fermion number. In particular, in the
low-energy limit we demonstrate the equivalence of the atomic Hamiltonian to a
relativistic Dirac Hamiltonian describing fractionalization in quantum field
theory. Expanding on our earlier argument [Phys. Rev. Lett. 91, 150404 (2003)]
we show how the fractional eigenvalues of the particle number operator can be
detected via light scattering. In particular, we show how scattering of far-off
resonant light can convey information about the counting statistics of the
atoms in an optical lattice, including state-selective atom density profiles
and atom number fluctuations. Optical detection could provide a truly quantum
mechanical measurement of the particle number fractionalization in a dilute
atomic gas.
\\ ( http://arxiv.org/abs/0709.2187 , 311kb)
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arXiv:0709.2193
Date: Fri, 14 Sep 2007 01:05:57 GMT (998kb)
Title: Radially Symmetric Nonlinear States of Harmonically Trapped
Bose-Einstein Condensates
Authors: G. Herring, L. D. Carr, R. Carretero-Gonzalez, P. G. Kevrekidis, and
D. J. Frantzeskakis
Categories: cond-mat.other
Comments: 10 pages, 16 figures (some with low resolution)
\\
Starting from the spectrum of the radially symmetric quantum harmonic
oscillator in two dimensions, we create a large set of nonlinear solutions. The
relevant three principal branches, with $n_r=0,1$ and 2 radial nodes
respectively, are systematically continued as a function of the chemical
potential and their linear stability is analyzed in detail, in the absence as
well as in the presence of topological charge $m$, i.e., vorticity. It is found
that for repulsive interatomic interactions {\it only} the ground state is {\it
linearly stable} throughout the parameter range examined. Furthermore, this is
true for topological charges $m=0$ or $m=1$; solutions with higher topological
charge can be unstable even in that case. All higher excited states are found
to be unstable in a wide parametric regime. However, for the
focusing/attractive case the ground state with $n_r=0$ and $m=0$ can only be
stable for a sufficiently low number of atoms. Once again, excited states are
found to be generically unstable. For unstable profiles, the dynamical
evolution of the corresponding branches is also followed to monitor the
temporal development of the instability.
\\ ( http://arxiv.org/abs/0709.2193 , 998kb)
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arXiv:0709.2212
Date: Fri, 14 Sep 2007 06:30:22 GMT (122kb)
Title: Molecular Bose-Einstein condensation in a versatile low power crossed
dipole trap
Authors: J. Fuchs, G. J. Duffy, G. Veeravalli, P. Dyke, M. Bartenstein, C. J.
Vale, P. Hannaford and W. J. Rowlands
Categories: cond-mat.other
Comments: 12 pages, 6 figures, submitted to J. Phys. B
\\
We produce Bose-Einstein condensates of 6Li2 molecules in a low power (22 W)
crossed optical dipole trap. Fermionic 6Li atoms are collected in a
magneto-optical trap from a Zeeman slowed atomic beam, then loaded into the
optical dipole trap where they are evaporatively cooled to quantum degeneracy.
Our simplified system offers a high degree of flexibility in trapping geometry
for studying ultracold Fermi and Bose gases.
\\ ( http://arxiv.org/abs/0709.2212 , 122kb)
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arXiv:0709.2273
Date: Fri, 14 Sep 2007 12:18:49 GMT (307kb)
Title: Multi-component strongly attractive Fermi gas: a color superconductor in
a one-dimensional harmonic trap
Authors: Xia-Ji Liu, Hui Hu and Peter D. Drummond
Categories: cond-mat.supr-con cond-mat.stat-mech
Comments: 15 pages, 9 figures
\\
Recent advances in ultra-cold atomic Fermi gases make it possible to achieve
a fermionic superfluid with multiple spin components. In this context, any
mean-field description is expected to fail, owing to the presence of tightly
bound clusters or molecules that consist of more than two particles. Here we
present a detailed study of a strongly interacting multi-component Fermi gas in
a highly elongated or quasi-one-dimensional harmonic trap, which could be
readily obtained in experiment. By using the exact Bethe ansatz solution and a
local density approximation treatment of the harmonic trap, we investigate the
equation of state of the multi-component Fermi gas in both a homogeneous and
trapped environment, as well as the density profiles and low-energy collective
modes. The binding energy of multi-component bound clusters is also given. We
show that there is a peak in the collective mode frequency at the critical
density for a deconfining transition to a many-body state that is analogous to
the quark color superconductor state expected in neutron stars.
\\ ( http://arxiv.org/abs/0709.2273 , 307kb)
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arXiv:0709.1986
Date: Thu, 13 Sep 2007 03:50:11 GMT (18kb)
Title: Quantum walk and quantum phase transition in optical lattice
Authors: C. M. Chandrashekar and Raymond Laflamme
Categories: quant-ph cond-mat.other physics.atom-ph
Comments: 4 pages, 5 figures
\\
We show that the quantum walk and its properties can be exploited to
redistribute the ultra-cold atoms in optical lattice into desired density
profile and quadratically speed up the the process of quantum phase transition.
We show this by evolving the density profile with every step of quantum walk by
numerical integration, where the correlation during the evolution can be
theoretically studied. We also discuss, how this can be implemented in the
realistic physical situations.
\\ ( http://arxiv.org/abs/0709.1986 , 18kb)
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rXiv:0709.2237
Date: Fri, 14 Sep 2007 09:20:57 GMT (402kb)
Title: An efficient source of continuous variable polarisation entanglement
Authors: Ruifang Dong, Joel Heersink, Jun-ichi Yoshikawa, Oliver Gloeckl, Ulrik
L. Andersen, Gerd Leuchs
Categories: quant-ph
Comments: 13 pages, 5 figures
\\
We have experimentally demonstrated the efficient creation of highly
entangled bipartite continuous variable polarisation states. Exploiting an
optimised scheme for the production of squeezing using the Kerr non-linearity
of a glass fibre we generated polarisation squeezed pulses with a mean
classical excitation in S3. Polarisation entanglement was generated by
interfering two independent polarisation squeezed fields on a symmetric beam
splitter. The resultant beams exhibit strong quantum noise correlations in the
dark S1 - S2 polarisation plane. To verify entanglement generation, we
characterised the quantum correlations of the system for two different sets of
conjugate Stokes parameters. The quantum correlations along the squeezed and
the anti-squeezed Stokes parameters were observed to be -4.1 +/- 0.3 dB and
-2.6 +/- 0.3 dB below the shot noise level respectively. The degree of
correlations was found to depend critically on the beam splitting ratio of the
entangling beam splitter. Carrying out measurements on a different set of
conjugate Stokes parameters, correlations of -3.6 +/- 0.3 dB and -3.4 +/- 0.3
dB have been observed. This result is more robust against asymmetries in the
entangling beam splitter, even in the presence of excess noise.
\\ ( http://arxiv.org/abs/0709.2237 , 402kb)
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arXiv:0709.2280
Date: Fri, 14 Sep 2007 12:50:40 GMT (271kb)
Title: Raman-induced limits to efficient squeezing in optical fibers
Authors: Ruifang Dong, Joel Heersink, Joel F. Corney, Peter D. Drummond, Ulrik
L. Andersen and Gerd Leuchs
Categories: quant-ph
Comments: 3 pages, 3 figures
\\
We report new experiments on polarization squeezing using ultrashort photonic
pulses in a single pass of a birefringent fiber. We measure what is to our
knowledge a record squeezing of -6.8 +/- 0.3 dB in optical fibers which when
corrected for linear losses is -10.4 +/- 0.8 dB. The measured polarization
squeezing as a function of optical pulse energy, which spans a wide range from
3.5-178.8 pJ, shows a very good agreement with the quantum simulations and for
the first time we see the experimental proof that Raman effects limit and
reduce squeezing at high pulse energy.
\\ ( http://arxiv.org/abs/0709.2280 , 271kb)
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arXiv:0709.2374
Date: Fri, 14 Sep 2007 20:00:01 GMT (10kb)
Title: Correlations in an expanding gas of hard-core bosons
Authors: D. M. Gangardt, M. Pustilnik
Categories: cond-mat.stat-mech
\\
We consider a longitudinal expansion of a one-dimensional gas of hard-core
bosons suddenly released from a trap. We show that the broken translational
invariance in the initial state of the system is encoded in correlations
between the bosonic occupation numbers in the momentum space. The correlations
are protected by the integrability and exhibit no relaxation during the
expansion.
\\ ( http://arxiv.org/abs/0709.2374 , 10kb)
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arXiv:0709.2386
Date: Fri, 14 Sep 2007 20:54:04 GMT (128kb)
Title: The one-dimensional Bose-Fermi-Hubbard model in the heavy-fermion limit
Authors: A. Mering and M. Fleischhauer
Categories: cond-mat.other
Comments: 12 pages, 15 figures
\\
We study the phase diagram of the zero-temperature, one-dimensional
Bose-Fermi-Hubbard model for fixed fermion density in the limit of small
fermionic hopping. This model can be regarded as an instance of a disordered
Bose-Hubbard model with dichotomic values of the stochastic variables. Phase
boundaries between compressible, incompressible (Mott-insulating) and partially
compressible phases are derived analytically within a generalized
strong-coupling expansion and numerically using density matrix renormalization
group (DMRG) methods. We provide evidence that the partially compressible
phases correspond to glass phases with exponentially decaying first-order
correlations. Fluctuations within the respective incompressible phases are
determined using perturbation theory and are compared to DMRG results.
\\ ( http://arxiv.org/abs/0709.2386 , 128kb)
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arXiv:0709.2501
Date: Sun, 16 Sep 2007 16:34:23 GMT (29kb)
Title: Generalized vorticity in transitional quantum turbulence
Authors: A. Bershadskii
Categories: cond-mat.other
\\
Transition to condensate state in the degenerate gas of bosons is studied
using the Gross-Pitaevskii equation. It is shown that adiabatic invariance of
an enstrophy (mean squared vorticity) based on a generalized vorticity $curl
(|\psi^2|{\bf v})/|\psi^2|$, controls dynamics of the transitional turbulence
just before formation of the condensate with its tangles of quantized vortices
($|\psi^2|{\bf v}$ is the weighted velocity field defined on the macroscopic
wave function $\psi$). Scaling of the angle-averaged occupation number
spectrum, $N_k \sim k^{-1}$, has been obtained for the free developing
transitional turbulence for the weak nonlinear (and completely disordered)
initial conditions. Results of the three-dimensional numerical simulations have
been used to support the theoretical consideration.
\\ ( http://arxiv.org/abs/0709.2501 , 29kb)
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arXiv:0709.2530
Date: Mon, 17 Sep 2007 06:08:07 GMT (40kb)
Title: Three-boson problem at low energy and Implications for dilute
Bose-Einstein condensates
Authors: Shina Tan
Categories: cond-mat.stat-mech
Comments: 24 pages, no figure
\\
It is shown that the effective interaction strength of three bosons at small
collision energies can be extracted from their wave function at zero energy. An
asymptotic expansion of this wave function at large interparticle distances is
derived, from which is defined a quantity $D$ named three-body scattering
hypervolume, which is an analog of the two-body scattering length. Given any
finite-range interaction potentials, one can thus predict the effective
three-body force from a numerical solution of the Schr\"{o}dinger equation. In
this way the constant $D$ for hard-sphere bosons is computed, leading to the
complete result for the ground state energy per particle of a dilute
Bose-Einstein condensate (BEC) of hard spheres to order $\rho^2$, where $\rho$
is the number density. Effects of $D$ are also demonstrated in the three-body
energy in a finite box of size $L$, which is expanded to the order $L^{-7}$,
and in the three-body scattering amplitude in vacuum. Another key prediction is
that there is a violation of the effective field theory (EFT) in the condensate
fraction in dilute BECs, caused by short-range physics. EFT predictions for the
ground state energy and few-body scattering amplitudes, however, are
corroborated.
\\ ( http://arxiv.org/abs/0709.2530 , 40kb)
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arXiv:0709.2621
Date: Mon, 17 Sep 2007 16:15:31 GMT (16kb)
Title: BCS-BEC crossover in a random external potential
Authors: G. Orso
Categories: cond-mat.supr-con
Comments: 4 pages, 2 figures
\\
We investigate the ground state properties of a disordered superfluid Fermi
gas across the BCS-BEC (Bose Einstein condensate) crossover. We show that, for
weak disorder, both the depletion of the condensate fraction of pairs and the
normal fluid density exhibit a nonmonotonic behavior as a function of the
interaction parameter $1/k_Fa$, reaching their minimum value near unitarity. We
find that, moving away from the weak coupling BCS regime, Anderson's theorem
ceases to apply and the superfluid order parameter is more and more affected by
the random potential.
\\ ( http://arxiv.org/abs/0709.2621 , 16kb)
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arXiv:0709.2653
Date: Mon, 17 Sep 2007 14:39:45 GMT (506kb)
Title: Quantum Fluctuations in the Superfluid State of the BCS-BEC Crossover
Authors: Roberto B. Diener, Rajdeep Sensarma, Mohit Randeria
Categories: cond-mat.other cond-mat.supr-con
Comments: 23 pages, 11 figures
\\
We determine the effects of quantum fluctuations about the T=0 mean field
solution of the BCS-BEC crossover in a dilute Fermi gas using the functional
integral method. These fluctuations are described in terms of the zero point
motion of collective modes and the virtual scattering of gapped quasiparticles.
We calculate their effects on various measurable properties, including chemical
potential, ground state energy, the gap, the speed of sound and the Landau
critical velocity. At unitarity, we find excellent agreement with quantum Monte
Carlo and experimental results. In the BCS limit, we show analytically that we
obtain Fermi liquid interaction corrections to thermodynamics including the
Hartree shift. In the BEC limit, we show that the theory leads to an
approximate description of the reduction of the scattering length for bosonic
molecules and also obtain quantum depletion of the Lee-Yang form. At the end of
the paper, we describe a method to include feedback of quantum fluctuations
into the gap equation, and discuss the problems of self-consistent calculations
in satisfying Goldstone's theorem and obtaining ultraviolet finite results at
unitarity.
\\ ( http://arxiv.org/abs/0709.2653 , 506kb)
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arXiv:0709.2425
Date: Sat, 15 Sep 2007 13:11:54 GMT (28kb)
Title: Detection of acceleration radiation in a Bose-Einstein condensate
Authors: A. Retzker, J. I. Cirac, M. B. Plenio, B. Reznik
Categories: quant-ph
Comments: 5 pages, 3 figures
\\
We propose and study methods for detecting the Unruh effect in a
Bose-Einstein condensate. The Bogoliubov vacuum of a Bose-Einstein condensate
is used here to simulate a scalar field-theory, and accelerated atom dots or
optical lattices as means for detecting phonon radiation due to acceleration
effects. We study Unruh's effect for linear acceleration and circular
acceleration. In particular, we study the dispersive effects of the Bogoliubov
spectrum on the ideal case of exact thermalization. Our results suggest that
Unruh's acceleration radiation can be tested using current accessible
experimental methods.
\\ ( http://arxiv.org/abs/0709.2425 , 28kb)
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arXiv:0709.2636
Date: Mon, 17 Sep 2007 13:51:28 GMT (178kb)
Title: Controlled deflection of a cold atomic cloud
Authors: Naceur Gaaloul (PPM, LSAMA), Laurence Pruvost (LAC), Mourad Telmini
(LSAMA), Eric Charron (PPM)
Categories: quant-ph
Proxy: ccsd hal-00172635
\\
We present a detailed, realistic proposal and analysis of the implementation
of a cold atom deflector using time-dependent far off-resonance optical guides.
An analytical model and numerical simulations are used to illustrate its
characteristics. We show that it is possible to deflect almost entirely a cloud
of $^{87}$Rb falling in the gravity field with angles reaching up to 25
degrees, using for all relevant parameters values that are achieved with
present technology. We discuss the limits of this proposed setup, and
illustrate its strong robustness against non-adiabatic transitions.
\\ ( http://arxiv.org/abs/0709.2636 , 178kb)
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arXiv:0709.2757
Date: Tue, 18 Sep 2007 15:44:52 GMT (15kb)
Title: Tkachenko modes in a superfluid Fermi gas at unitarity
Authors: Gentaro Watanabe, Marco Cozzini, and Sandro Stringari
Categories: cond-mat.other cond-mat.supr-con
Comments: 4 pages, 1 figure, submitted to PRA rapid communications
\\
We calculate the frequencies of the Tkachenko oscillations of a vortex
lattice in a harmonically trapped superfluid Fermi gas. We use the
elasto-hydrodynamic theory by properly accounting for the elastic constants,
the Thomas-Fermi density profile of the atomic cloud, and the boundary
conditions. Thanks to the Fermi pressure, which is responsible for larger cloud
radii with respect to the case of dilute Bose-Einstein condensed gases, large
vortex lattices are achievable in the unitary limit of infinite scattering
length, even at relatively small angular velocities. This opens the possibility
of experimentally observing vortex oscillations in the regime where the
dispersion relation approaches the Tkachenko law for incompressible fluids and
the mode frequency is almost comparable to the trapping frequencies.
\\ ( http://arxiv.org/abs/0709.2757 , 15kb)
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arXiv:0709.2747
Date: Tue, 18 Sep 2007 02:35:47 GMT (312kb)
Title: Spin squeezing and maximal-squeezing time
Authors: Guang-Ri Jin and Sang Wook Kim
Categories: quant-ph
Comments: 7 pages, 5 figures, 1 table. Resubmitted to Phys. Rev. A
\\
Spin squeezing of a nonlinear interaction model with Josephson-like coupling
is studied to obtain time scale of maximal squeezing. Based upon two exactly
solvable cases for two and three particles, we find that the maximal-squeezing
time depends on the level spacing between the ground state and its next
neighbor eigenstate.
\\ ( http://arxiv.org/abs/0709.2747 , 312kb)
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arXiv:0709.2749
Date: Tue, 18 Sep 2007 03:18:09 GMT (898kb)
Title: Single Atoms on an Optical Nanofiber
Authors: K. P. Nayak and K. Hakuta
Categories: quant-ph
Comments: 4 pages, 5 figures
\\
We show that single-atoms can be trapped on the surface of a
subwavelength-diameter silica-fiber, an optical nanofiber, without any external
field, and that single photons spontaneously emitted from the atoms can be
readily detected through the single guided-mode of the nanofiber. A key point
of the work is our finding that atom trapping sites are created on the
nanofiber surface by irradiating the atom cloud around the nanofiber with a
violet laser radiation.
\\ ( http://arxiv.org/abs/0709.2749 , 898kb)
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arXiv:0709.2849
Date: Tue, 18 Sep 2007 15:26:34 GMT (343kb)
Title: Trapped Rydberg Ions
Authors: I. Lesanovsky, L.-M. Liang, M. Mueller, and P. Zoller
Categories: quant-ph
Comments: 5 pages, 3 figures
\\
We study the quantum dynamics of trapped ions in Rydberg states, which have
large electric dipole moments induced by the trapping fields. In the limit
where the localization of the ion core is much smaller than the Rydberg orbit
the dynamics of the system is determined by the interplay between large
dipole-dipole energy shifts and strong tunable internal-state-dependent forces
due to dipole-charge interactions. This provides a new tool for manipulating
and entangling ions by strong interactions and on fast time scales.
\\ ( http://arxiv.org/abs/0709.2849 , 343kb)
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arXiv:0709.2866
Date: Tue, 18 Sep 2007 16:52:13 GMT (150kb)
Title: Bose-Einstein condensates with attractive 1/r interaction: The case of
self-trapping
Authors: I. Papadopoulos, P. Wagner, G. Wunner, J. Main
Categories: quant-ph
Comments: 7 pages, 7 figures, to appear in Phys. Rev. A
\\
Amplifying on a proposal by O'Dell et al. for the realization of
Bose-Einstein condensates of neutral atoms with attractive $1/r$ interaction,
we point out that the instance of self-trapping of the condensate, without
external trap potential, is physically best understood by introducing
appropriate "atomic" units. This reveals a remarkable scaling property: the
physics of the condensate depends only on the two parameters $N^2 a/a_u$ and
$\gamma/N^2$, where $N$ is the particle number, $a$ the scattering length,
$a_u$ the "Bohr" radius and $\gamma$ the trap frequency in atomic units. We
calculate accurate numerical results for self-trapping wave functions and
potentials, for energies, sizes and peak densities, and compare with previous
variational results. As a novel feature we point out the existence of a second
solution of the extended Gross-Pitaevskii equation for negative scattering
lengths, with and without trapping potential, which is born together with the
ground state in a tangent bifurcation. This indicates the existence of an
unstable collectively excited state of the condensate for negative scattering
lengths.
\\ ( http://arxiv.org/abs/0709.2866 , 150kb)
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arXiv:0709.2841
Date: Tue, 18 Sep 2007 14:56:09 GMT (288kb)
Title: Trapping and cooling of rf-dressed atoms in a quadrupole magnetic field
Authors: Olivier Morizot (LPL), Carlos L. Garrido Alzar (LPL), Paul-Eric Pottie
(LPL), Vincent Lorent (LPL), H\'el\`ene Perrin (LPL)
Categories: physics.atom-ph
Comments: 6 pages, 6 figures; to appear in J. Phys. B
Proxy: ccsd hal-00173059
\\
We observe the spontaneous evaporation of atoms confined in a bubble-like
rf-dressed trap (Zobay and Garraway, 2001). The atoms are confined in a
quadrupole magnetic trap and are dressed by a linearly polarized rf field. The
evaporation is related to the presence of holes in the trap, at the positions
where the rf coupling vanishes, due to its vectorial character. The final
temperature results from a competition between residual heating and evaporation
efficiency, which is controlled via the height of the holes with respect to the
bottom of the trap. The experimental data are modeled by a Monte-Carlo
simulation predicting a small increase in phase space density limited by the
heating rate. This increase was within the phase space density determination
uncertainty of the experiment.
\\ ( http://arxiv.org/abs/0709.2841 , 288kb)
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arXiv:0709.2934
Date: Tue, 18 Sep 2007 22:54:51 GMT (174kb)
Title: Quantum Hall Transition near a Fermion Feshbach Resonance in a Rotating
Trap
Authors: Kun Yang and Hui Zhai
Categories: cond-mat.mes-hall cond-mat.str-el
Comments: 4 pages with one embedded figure
\\
We consider two-species of fermions in a rotating trap that interact via an
s-wave Feshbach resonance, at total Landau level filling factor two (or one for
each species). We show that the system undergoes a quantum phase transition
from a fermion integer quantum Hall state to a boson fractional quantum Hall
state as the pairing interaction strength increases, with the transition
occurring near the resonance. The effective field theory for the transition is
shown to be that of a (emergent) massless relativistic bosonic field coupled to
a Chern-Simons gauge field, with the coupling giving rise to semionic
statistics to the emergent particles.
\\ ( http://arxiv.org/abs/0709.2934 , 174kb)
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arXiv:0709.3017
Date: Wed, 19 Sep 2007 13:47:21 GMT (75kb)
Title: Emergent fermions and anyons in the Kitaev model
Authors: K. P. Schmidt, S. Dusuel, J. Vidal
Categories: cond-mat.other
Comments: 4 pages, 5 figures
\\
We study the gapped phase of the Kitaev model on the honeycomb lattice using
perturbative continuous unitary transformations. The effective low-energy
Hamiltonian is found to be an extended toric code with interacting anyons.
High-energy excitations are emerging free fermions which are composed of
hardcore bosons with an attached string of spin operators. The excitation
spectrum is mapped onto that of a single particle hopping on a square lattice
in a magnetic field. The present approach yields analytical perturbative
results in the thermodynamical limit and gives a simple description of the
spectrum without using the Majorana or the Jordan-Wigner fermionization
initially proposed to solve this problem.
\\ ( http://arxiv.org/abs/0709.3017 , 75kb)
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arXiv:0709.3027
Date: Wed, 19 Sep 2007 14:43:33 GMT (342kb,D)
Title: Phase diagram of a two-component Fermi gas with resonant interactions
Authors: Yong-il Shin, Christian H. Schunck, Andre Schirotzek, Wolfgang
Ketterle
Categories: cond-mat.soft
Comments: 8 pages, 8 figures
\\
The pairing of fermions is at the heart of superconductivity and
superfluidity. The recent experimental realization of strongly interacting
atomic Fermi gases has opened a new, controllable way to study novel forms of
pairing and superfluidity. A major controversial issue has been the stability
of superfluidity against an imbalance between the two spin components when the
fermions interact resonantly. Here we present the phase diagram of a
spin-polarized Fermi gas of 6Li atoms at unitarity, mapping out the superfluid
phases versus temperature and density imbalance. Using tomographic techniques,
we reveal spatial discontinuities in the spin polarization, the signature of a
first-order phase transition, which disappears at a tricritical point. These
observations and the implementation of an in situ ideal gas thermometer provide
a quantitative test of theoretical calculations on the stability of resonant
superfluidity.
\\ ( http://arxiv.org/abs/0709.3027 , 342kb)
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arXiv:0709.3050
Date: Wed, 19 Sep 2007 16:04:26 GMT (576kb)
Title: Coherent tunneling by adiabatic passage in an optical waveguide system
Authors: S. Longhi, G. Della Valle, M. Ornigotti, and P. Laporta
Categories: cond-mat.other cond-mat.mes-hall
Comments: submitted for publication
\\
We report on the first experimental demonstration of light transfer in an
engineered triple-well optical waveguide structure which provides a classic
analogue of Coherent Tunnelling by Adiabatic Passage (CTAP) recently proposed
for coherent transport in space of neutral atoms or electrons among
tunneling-coupled optical traps or quantum wells [A.D. Greentree et al., Phys.
Rev. B 70, 235317 (2004); K. Eckert et al., Phys. Rev. A 70, 023606 (2004)].
The direct visualization of CTAP wavepacket dynamics enabled by our simple
optical system clearly shows that in the counterintuitive passage scheme light
waves tunnel between the two outer wells without appreciable excitation of the
middle well.
\\ ( http://arxiv.org/abs/0709.3050 , 576kb)
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arXiv:0709.3068
Date: Wed, 19 Sep 2007 16:53:22 GMT (935kb)
Title: Bose-Einstein Condensation of an Ytterbium Isotope
Authors: Takeshi Fukuhara, Seiji Sugawa, and Yoshiro Takahashi
Categories: cond-mat.other
Comments: 4 pages, 3 figures
\\
We report the observation of a Bose Einstein condensate in a bosonic isotope
of ytterbium (170Yb). More than 10^6 atoms are trapped in a crossed optical
dipole trap and cooled by evaporation. Condensates of approximately 10^4 atoms
have been obtained. From an expansion of the condensate, we have extracted the
scattering length a=3.6(9) nm.
\\ ( http://arxiv.org/abs/0709.3068 , 935kb)
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arXiv:0709.2996
Date: Wed, 19 Sep 2007 11:47:07 GMT (157kb,D)
Title: Entanglement-free Heisenberg-limited phase estimation
Authors: B. L. Higgins, D. W. Berry, S. D. Bartlett, H. M. Wiseman, G. J. Pryde
Categories: quant-ph
Comments: Accepted for publication in Nature. This is the original submitted
version, formatted 2-column
\\
Measurement underpins all quantitative science, and advances in precision
measurement have consistently led to new scientific discoveries. A key example
is the measurement of optical phase, used in length metrology and myriad other
applications. At the fundamental level, measurement precision is limited by the
number N of quantum resources (e.g. photons) that are used. Standard
measurement schemes, using each resource independently, lead to a phase
uncertainty scaling as 1/\sqrt{N} - the standard quantum limit (SQL). However,
it has long been conjectured that one should be able to achieve a precision
limited only by the Heisenberg uncertainty principle, dramatically improving
the scaling to 1/N . It is commonly held that to achieve this improvement
requires exotic states such as the "NOON" state. Unfortunately, the generation
of such states is extremely difficult - measurement schemes with counted
photons or ions have been performed with N <= 6, but few have surpassed the SQL
and none have shown Heisenberg-limited scaling. Here we perform the first
experimental demonstration of a Heisenberg-limited phase estimation procedure.
We replace entangled input states with multiple applications of the phase shift
on unentangled single-photon states. We generalize Kitaev's phase estimation
algorithm, using adaptive measurement theory, in order to achieve a standard
deviation scaling at the Heisenberg limit. For the largest number of resources
we use, N=378, we estimate an unknown phase with a variance more than 10 dB
below the SQL; achieving this variance would require more than 4,000 resources
using standard interferometry. Our results represent a drastic reduction in the
complexity of achieving quantum-enhanced measurement precision.
\\ ( http://arxiv.org/abs/0709.2996 , 157kb)
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rXiv:0709.3081
Date: Wed, 19 Sep 2007 17:59:09 GMT (18kb)
Title: Vibrational energy transfer in ultracold molecule - molecule collisions
Authors: Goulven Qu\'em\'ener, Naduvalath Balakrishnan, Roman V. Krems
Categories: quant-ph
Comments: 4 pages, 4 figures
\\
We present a rigorous study of vibrational relaxation in p-H2 - p-H2
collisions at cold and ultracold temperatures and identify a novel mechanism of
vibrational energy transfer. If the colliding molecules are in different
rotational and vibrational levels, the vibrational energy may be transferred
between the molecules through an extremely efficient and state-selective
process involving simultaneous vibrational excitation and de-excitation. If the
molecules are indistinguishable, this process corresponds to transfer of
rotational energy from one vibrational state of the colliding molecules to
another.
\\ ( http://arxiv.org/abs/0709.3081 , 18kb)
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\\
arXiv:0709.2924
Date: Tue, 18 Sep 2007 21:52:27 GMT (54kb)
Title: Feshbach resonances in ultracold ^{6,7}Li + ^{23}Na atomic mixtures
Authors: Marko Gacesa, Philippe Pellegrini, and Robin C\^ot\'e
Categories: physics.atom-ph
Comments: 4 pages, 2 figures
\\
We report a theoretical study of Feshbach resonances in a mixture of
$^{6,7}$Li and $^{23}$Na atoms at ultralow temperatures, using new accurate
interaction potentials in a full quantum coupled-channel calculation. Feshbach
resonances in the initial collision open channel $^6$Li$(f=1/2, m_f=1/2) +
^{23}$Na$(f=1, m_f=1)$ are found to agree with previous measurements, leading
to the first precise determination of the singlet and triplet scattering
lengths for the $^{6,7}$Li$+^{23}$Na pairs. We predict additional Feshbach
resonances within experimentally attainable magnetic fields for other collision
channels. Corresponding loss rates are also calculated.
\\ ( http://arxiv.org/abs/0709.2924 , 54kb)
------------------------------------------------------------------------------
\\
arXiv:0709.3137
Date: Thu, 20 Sep 2007 13:49:07 GMT (97kb)
Title: Observation of photon-assisted tunneling in optical lattices
Authors: C. Sias and H. Lignier and Y. P. Singh and A. Zenesini and D. Ciampini
and O. Morsch and E. Arimondo
Categories: cond-mat.soft
Comments: 5 pages, 3 figures
\\
We have observed tunneling suppression and photon-assisted tunneling of
Bose-Einstein condensates in an optical lattice subjected to a constant force
plus a sinusoidal shaking. For a sufficiently large constant force, the ground
energy levels of the lattice are shifted out of resonance and tunneling is
suppressed; when the shaking is switched on, the levels are coupled by
low-frequency photons and tunneling resumes. Our results agree well with
theoretical predictions and demonstrate the usefulness of optical lattices for
studying solid-state phenomena.
\\ ( http://arxiv.org/abs/0709.3137 , 97kb)
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\\
arXiv:0709.3158
Date: Thu, 20 Sep 2007 08:38:52 GMT (145kb,D)
Title: Twin peaks in rf spectra of Fermi gases at unitarity in the normal phase
Authors: P. Massignan, G. M. Bruun and H. T. C. Stoof
Categories: cond-mat.other cond-mat.str-el
Comments: 4 pages, 5 figures
\\
We calculate the radio-frequency spectrum of balanced and imbalanced
ultracold Fermi gases in the normal phase at unitarity. For the homogeneous
case, we find that the spectrum always has a single peak even in the pseudogap
regime. We demonstrate that the double-peaked structures observed for
intermediate temperatures in recent experiments are due to the presence of the
trap, with the shifted peak coming from the center of the cloud where the gas
is in the pseudogap regime and the unshifted peak coming from the edge where
the gas is very dilute. The main experimental features observed above the
critical temperature in the recent experiment of Schunck et al. [Science 316,
867 (2007)] are recovered with no fitting parameters.
\\ ( http://arxiv.org/abs/0709.3158 , 145kb)
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\\
arXiv:0709.3163
Date: Thu, 20 Sep 2007 09:19:49 GMT (431kb)
Title: Few-boson dynamics in double wells: From single-atom to correlated-pair
tunneling
Authors: Sascha Z\"ollner, Hans-Dieter Meyer and Peter Schmelcher
Categories: cond-mat.other
\\
We investigate few-boson tunneling in a one-dimensional double well, covering
the full crossover from weak interactions to the fermionization limit of strong
correlations. Based on exact quantum-dynamical calculations, it is found that
the tunneling dynamics of two atoms evolves from Rabi oscillations to
correlated pair tunneling as we increase the interaction strength. Near the
fermionization limit, fragmented-pair tunneling is observed and analyzed in
terms of the population imbalance and two-body correlations. For more atoms,
the tunneling dynamics near fermionization is shown to be sensitive to both
atom number and initial configuration.
\\ ( http://arxiv.org/abs/0709.3163 , 431kb)
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\\
arXiv:0709.3212
Date: Thu, 20 Sep 2007 12:23:41 GMT (556kb)
Title: Electrostatic trapping of metastable NH molecules
Authors: Steven Hoekstra, Markus Metsala, Peter C. Zieger, Ludwig Scharfenberg,
Joop J. Gilijamse, Gerard Meijer and Sebastiaan Y. T. van de Meerakker
Categories: physics.atom-ph physics.chem-ph
\\
We report on the Stark deceleration and electrostatic trapping of $^{14}$NH
($a ^1\Delta$) radicals. In the trap, the molecules are excited on the
spin-forbidden $A ^3\Pi \leftarrow a ^1\Delta$ transition and detected via
their subsequent fluorescence to the $X ^3\Sigma^-$ ground state. The 1/e
trapping time is 1.4 $\pm$ 0.1 s, from which a lower limit of 2.7 s for the
radiative lifetime of the $a ^1\Delta, v=0,J=2$ state is deduced. The spectral
profile of the molecules in the trapping field is measured to probe their
spatial distribution. Electrostatic trapping of metastable NH followed by
optical pumping of the trapped molecules to the electronic ground state is an
important step towards accumulation of these radicals in a magnetic trap.
\\ ( http://arxiv.org/abs/0709.3212 , 556kb)
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The replacements:
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\\
arXiv:0705.2015
replaced with revised version Fri, 14 Sep 2007 18:37:29 GMT (41kb)
Title: Dynamics of excitations in a one-dimensional Bose liquid
Authors: M. Khodas, M. Pustilnik, A. Kamenev, L.I. Glazman
Categories: cond-mat.stat-mech cond-mat.mes-hall
Journal-ref: Phys. Rev. Lett. 99, 110405 (2007)
DOI: 10.1103/PhysRevLett.99.110405
\\ ( http://arxiv.org/abs/0705.2015 , 41kb)
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\\
arXiv:cond-mat/0701786
replaced with revised version Mon, 17 Sep 2007 05:38:15 GMT (69kb)
Title: Thermodynamics of a Trapped Unitary Fermi Gas
Authors: Aurel Bulgac, Joaquin E. Drut, Piotr Magierski
Categories: cond-mat.stat-mech nucl-th physics.atom-ph
Comments: 4 pages, 4 figures
\\ ( http://arxiv.org/abs/cond-mat/0701786 , 69kb)
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\\
arXiv:0705.2320
replaced with revised version Sun, 16 Sep 2007 10:38:35 GMT (8kb)
Title: The Localization Length of Stationary States in the Nonlinear
Schreodinger Equation
Authors: Alexander Iomin and Shmuel Fishman
Categories: cond-mat.dis-nn astro-ph nlin.CD
\\ ( http://arxiv.org/abs/0705.2320 , 8kb)
------------------------------------------------------------------------------
\\
arXiv:physics/0607034
replaced with revised version Mon, 17 Sep 2007 07:21:12 GMT (279kb)
Title: A Radio-Frequency Atom Chip for Guiding Neutral Atoms
Authors: Xiaolin Li, Haichao Zhang, Bo Yan, Min Ke, Yuzhu Wang
Categories: physics.atom-ph
\\ ( http://arxiv.org/abs/physics/0607034 , 279kb)
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\\
arXiv:0704.2299
replaced with revised version Mon, 17 Sep 2007 08:43:11 GMT (424kb)
Title: One-dimensional Rydberg Gas in a Magnetoelectric Trap
Authors: Michael Mayle, Bernd Hezel, Igor Lesanovsky and Peter Schmelcher
Categories: physics.atom-ph
Comments: 4 pages, 2 figures
Journal-ref: Phys. Rev. Lett. 99, 113004 (2007)
DOI: 10.1103/PhysRevLett.99.113004
\\ ( http://arxiv.org/abs/0704.2299 , 424kb)
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\\
arXiv:math-ph/0611043 (*cross-listing*)
replaced with revised version Tue, 18 Sep 2007 19:41:25 GMT (20kb)
Title: Interacting Bose and Fermi gases in low dimensions and the Riemann
hypothesis
Authors: Andr\'e LeClair
Categories: math-ph cond-mat.stat-mech hep-th math.MP math.NT
Comments: version 3: additional appendix explains how the $\nu$ to $1-\nu$
duality of Riemann's $\zeta (\nu)$ follows from a special modular
transformation in a massless relativistic theory
\\ ( http://arxiv.org/abs/math-ph/0611043 , 20kb)
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\\
arXiv:0707.0792
replaced with revised version Tue, 18 Sep 2007 16:08:35 GMT (63kb)
Title: Theory of RF-spectroscopy of strongly interacting Fermions
Authors: M. Punk, W. Zwerger
Categories: cond-mat.other
Comments: revised version, 4 pages, 3 figures, RevTex4
\\ ( http://arxiv.org/abs/0707.0792 , 63kb)
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\\
arXiv:0707.3003
replaced with revised version Mon, 17 Sep 2007 23:17:04 GMT (553kb)
Title: Energy Dependence of Scattering Ground State Polar Molecules
Authors: Christopher Ticknor
Categories: physics.atom-ph
Comments: Accepted PRA, 10 pages, 5 figures
\\ ( http://arxiv.org/abs/0707.3003 , 553kb)
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rXiv:0704.3867
replaced with revised version Thu, 20 Sep 2007 07:22:10 GMT (213kb)
Title: Inhibited Feshbach Conversion of Atomic Fermions to Molecular Bosons due
to Particle Interactions
Authors: Jie Liu, Li-Bin Fu, Bin Liu, Shi-Ping Yang and Biao Wu
Categories: cond-mat.mes-hall
Comments: 5 pages, 4 figures
\\ ( http://arxiv.org/abs/0704.3867 , 213kb)
------------------------------------------------------------------------------
\\
arXiv:0705.3956
replaced with revised version Thu, 20 Sep 2007 11:24:05 GMT (25kb)
Title: Boson Mott insulators at finite temperatures
Authors: Fabrice Gerbier (LKB - Lhomond)
Categories: cond-mat.other
Proxy: ccsd hal-00149582
Journal-ref: Physical Review Letters 99 (2007) 120405
DOI: 10.1103/PhysRevLett.99.120405
\\ ( http://arxiv.org/abs/0705.3956 , 25kb)
------------------------------------------------------------------------------
\\
arXiv:0706.1170
replaced with revised version Thu, 20 Sep 2007 09:44:39 GMT (180kb)
Title: A lattice of microtraps for ultracold atoms based on patterned magnetic
films
Authors: R. Gerritsma, S. Whitlock, T. Fernholz, H. Schlatter, J. A. Luigjes,
J.-U. Thiele, J. B. Goedkoop and R. J. C. Spreeuw
Categories: physics.atom-ph
Comments: 7 pages, 7 figures
Journal-ref: Phys. Rev. A 76, 033408 (2007)
\\ ( http://arxiv.org/abs/0706.1170 , 180kb)
------------------------------------------------------------------------------
Till next time,
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/ ========================================================================= Legal stuff: Unless stated otherwise, this e-mail represents only the views of the sender and not the views of the University of Queensland =========================================================================Received on Sat Oct 13 2007 - 22:58:09 EST
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