Dear subscribers,
This week's selection was compiled by Mike Garrett, and contains 32 new
abstracts and 15 replacements.
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arXiv:1008.2239
Date: Fri, 13 Aug 2010 00:43:34 GMT (734kb)
Title: Neutral skyrmion configurations in the low-energy effective theory of
spinor condensate ferromagnets
Authors: R. W. Cherng and E. Demler
Categories: cond-mat.quant-gas
Comments: 13 pages, 7 figures
\\
We study the low-energy effective theory of spinor condensate ferromagnets
for the superfluid velocity and magnetization degrees of freedom. This
effective theory describes the competition between spin stiffness and a
long-ranged interaction between skyrmions, topological objects familiar from
the theory of ordinary ferromagnets. We find exact solutions to the non-linear
equations of motion describing neutral configurations of skyrmions and
anti-skyrmions. These analytical solutions provide a simple physical picture
for the origin of crystalline magnetic order in spinor condensate ferromagnets
with dipolar interactions. We also point out the connections to effective
theories for quantum Hall ferromagnets.
\\ ( http://arxiv.org/abs/1008.2239 , 734kb)
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arXiv:1008.2240
Date: Fri, 13 Aug 2010 00:48:45 GMT (334kb)
Title: Symmetry analysis of crystalline spin textures in dipolar spinor
condensates
Authors: R. W. Cherng and E. Demler
Categories: cond-mat.quant-gas
Comments: 19 pages, 4 figures
\\
We study periodic crystalline spin textures in spinor condensates with
dipolar interactions via a systematic symmetry analysis of the low-energy
effective theory. By considering symmetry operations which combine real and
spin space operations, we classify symmetry groups consistent with non-trivial
experimental and theoretical constraints. Minimizing the energy within each
symmetry class allows us to explore possible ground states.
\\ ( http://arxiv.org/abs/1008.2240 , 334kb)
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arXiv:1008.2260
Date: Fri, 13 Aug 2010 07:36:00 GMT (1425kb,D)
Title: The Efimov effect in lithium 6
Authors: Pascal Naidon and Masahito Ueda
Categories: cond-mat.quant-gas physics.atom-ph
Comments: 12 pages, 8 figures
\\
We analyse the recent experiments investigating the low-energy physics of
three lithium 6 atoms in different internal states with resonant two-body
scattering lengths. All observed features are qualitatively consistent with the
expected Efimov effect, i.e. the effective universal three-body attraction that
arises for large values of the scattering lengths. However, we find that a
quantitative description at negative energy requires non-universal two- and
three-body corrections due to presently unknown behaviour at short distance. An
attempt to implement these corrections is made through energy-dependent
parameters fitted to the experimental data.
\\ ( http://arxiv.org/abs/1008.2260 , 1425kb)
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arXiv:1008.2263
Date: Fri, 13 Aug 2010 07:51:59 GMT (10kb)
Title: Bose-Einstein Condensation in an artificial spin-orbit interaction
Authors: S.-K. Yip
Categories: cond-mat.quant-gas
Comments: 5 pages, no figures
\\
Bose-Einstein condensation in the presence of a synthetic spin-momentum
interaction is considered, focusing on the case where a Dirac or Rashba
potential is generated via a tripod scheme. We found that the ground states can
be either plane wave states or superpositions of them, each characterized by
their unique density distributions.
\\ ( http://arxiv.org/abs/1008.2263 , 10kb)
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arXiv:1008.2324
Date: Fri, 13 Aug 2010 14:16:44 GMT (609kb)
Title: Creation of topological states of a Bose-Einstein condensate in a
plaquette
Authors: Tomasz \'Swis{\l}ocki, Miros{\l}aw Brewczyk, and Mariusz Gajda
Categories: cond-mat.quant-gas cond-mat.other
\\
We study a square plaquette of four optical traps containing ultracold
$^{87}$Rb atoms in $F=1$ hyperfine state. In a presence of external resonant
magnetic field the dipolar interactions couple initial $m_F=1$ component to
other Zeeman sublevels. We find that topological properties of final atomic
states are determined by the competition between the local axial symmetry of
individual trap and the discrete symmetry of the plaquette. In deep axially
symmetric traps a vortex superfluid is created in $m_F=0$ component with
vortices localized at individual traps whereas for shallow traps a discrete
single vortex appears in the final state. States created in these opposite
cases have different topological properties related to $C_4$ point-symmetry.
\\ ( http://arxiv.org/abs/1008.2324 , 609kb)
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arXiv:1008.2326 (*cross-listing*)
Date: Fri, 13 Aug 2010 14:18:53 GMT (283kb)
Title: Quantum zigzag transition in interacting atom chains
Authors: Efrat Shimshoni, Giovanna Morigi, Shmuel Fishman
Categories: cond-mat.stat-mech quant-ph
Comments: 4 pages, 1 figure
\\
A string of trapped interacting ions at zero temperature ($T=0$) exhibits a
structural phase transition to a zigzag structure, tuned by reducing the
transverse trap potential or increasing the particle density. The transition is
driven by transverse, short wavelength vibrational modes. We propose a quantum
field--theoretical description of this transition by the one dimensional Ising
model in a transverse field. Based on the mapping to this model, we estimate
the quantum critical point in terms of the system parameters, and find a
finite, measurable deviation from the critical point predicted by the classical
theory. A measurement procedure is suggested which can probe the effects of
quantum fluctuations at criticality. These results can be extended to describe
the transverse instability of ultracold polar molecules in a one dimensional
optical lattice.
\\ ( http://arxiv.org/abs/1008.2326 , 283kb)
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arXiv:1008.2431
Date: Sat, 14 Aug 2010 10:56:10 GMT (1496kb)
Title: Observation of spontaneous Bose-Einstein condensation of excitons at
sub-Kelvin temperatures
Authors: Kosuke Yoshioka, Eunmi Chae and Makoto Kuwata-Gonokami
Categories: cond-mat.quant-gas
Comments: 18 pages, 5 figures, Supplementary Information (8 pages, 3 figures)
included
\\
Bose-Einstein condensation (BEC) is a quantum mechanical phenomenon directly
linked to the quantum statistics of bosons. While cold atomic gases provide a
new arena for exploring the nature of BEC, a long-term quest to confirm BEC of
excitons, quasi-Bose particles formed as a bound state of an electron-hole
pair, has been underway since its theoretical prediction in the 1960s.
Ensembles of electrons and holes are complex quantum systems with strong
Coulomb correlations; thus, it is non-trivial whether nature chooses a form of
exciton BEC. Various systems have been examined in bulk and two-dimensional
semiconductors and also exciton-photon hybrid systems. Among them, the 1s
paraexciton state in a single crystal of Cu2O has been a prime candidate for
realizing three-dimensional BEC. The large binding energy and long lifetime
enable preparation of cold excitons in thermal equilibrium with the lattice and
decoupled from the radiation field. However, collisional loss severely limits
the conditions for reaching BEC. Such a system with a large inelastic cross
section is excluded in atomic BEC experiments, where a small inelastic
scattering rate and efficient elastic scattering are necessary for evaporative
cooling. Here we demonstrate that it is nevertheless possible to achieve BEC by
cooling paraexcitons to sub-Kelvin temperatures in a cold phonon bath. Emission
spectra from paraexcitons in a three-dimensional trap show an anomalous
distribution in a threshold-like manner at the critical number of BEC expected
for ideal bosons. Bosonic stimulated scattering into the condensate and
collisional loss compete and limit the condensate to a fraction of about 1%.
This observation adds a new class of experimentally accessible BEC for
exploring a rich variety of matter phases of electron-hole ensembles.
\\ ( http://arxiv.org/abs/1008.2431 , 1496kb)
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arXiv:1008.2444
Date: Sat, 14 Aug 2010 13:27:50 GMT (129kb)
Title: Two-dimensional scattering and bound states of polar molecules in
bilayers
Authors: Michael Klawunn, Alexander Pikovski and Luis Santos
Categories: cond-mat.quant-gas math-ph math.MP
Comments: 4 pages, 3 figures
\\
Low-energy two-dimensional scattering is particularly sensitive to the
existence and properties of weakly-bound states. We show that interaction
potentials $V(r)$ with vanishing zero-momentum Born approximation $\int d^2r
V(r)=0$ lead to an anomalously weak bound state which crucially modifies the
two-dimensional scattering properties. This anomalous case is especially
relevant in the context of polar molecules in bilayer arrangements.
\\ ( http://arxiv.org/abs/1008.2444 , 129kb)
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arXiv:1008.2572
Date: Mon, 16 Aug 2010 05:09:11 GMT (78kb,D)
Title: W-states from Bose-Einstein condensates in an optical cavity
Authors: B.M. Rodr\'{\i}guez-Lara and Ray-Kuang Lee
Categories: quant-ph
Comments: 11 pages, 2 figures
\\
We analytically investigate the ground state of a Bose-Einstein condensate of
bosonic atoms with two hyperfine structures inside an optical cavity within the
cavity quantum electrodynamics formalism. The system allows a series of quantum
phase transitions. The critical coupling value at the first quantum phase
transition of the system is calculated and the maximum shared bipartite
entanglement of the condensate is studied numerically. We reveal the existence
of a maximum entangled multipartite qubit state, a W-state, for certain
parameters at the first non-vacuum phase region of the system due to finite
size effects.
\\ ( http://arxiv.org/abs/1008.2572 , 78kb)
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arXiv:1008.2662
Date: Mon, 16 Aug 2010 14:14:57 GMT (280kb)
Title: Toward scalable information processing with ultracold polar molecules in
an electric field: a numerical investigation
Authors: La\"etitia Bomble and Philippe Pellegrini and Pierre Ghesqui\`ere and
Mich\`ele Desouter-Lecomte
Categories: quant-ph
\\
We numerically investigate the possibilities of driving quantum algorithms
with laser pulses in a register of ultracold NaCs polar molecules in a static
electric field. We focuse on the possibilities of performing scalable logical
operations by considering circuits that involve intermolecular gates
(implemented on adjacent interacting molecules) to enable the transfer of
information from one molecule to another during conditional laser-driven
population inversions. We study the implementation of an arithmetic operation
(the addition of 0 or 1 on a binary digit and a carry in) which requires
population inversions only and the Deutsch-Josza algorithm which requires a
control of the phases. Under typical experimental conditions, our simulations
show that high fidelity logical operations involving several qubits can be
performed in a time scale of a few hundred of microseconds, opening promising
perspectives for the manipulation of a large number of qubits in these systems.
\\ ( http://arxiv.org/abs/1008.2662 , 280kb)
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arXiv:1008.2778
Date: Mon, 16 Aug 2010 21:40:07 GMT (124kb)
Title: Controlling free superflow, dark matter and luminescence rings of
excitons in quantum well structures
Authors: A. S. Alexandrov and S. E. Savel'ev
Categories: cond-mat.mes-hall
Comments: 6 pages, 4 figures, 1 supplement with 1 figure, 2 animations
\\
Following the discovery of Bose-Einstein condensation (BEC) in ultra cold
atoms [E. Gosta, Nobel Lectures in Physics (2001-2005), World Scientific
(2008)], there has been a huge experimental and theoretical push to try and
illuminate a superfluid state of Wannier-Mott excitons. Excitons in quantum
wells, generated by a laser pulse, typically diffuse only a few micrometers
from the spot they are created. However, Butov et al. and Snoke et al. reported
luminescence from indirect and direct excitons hundreds of micrometers away
from the laser excitation spot in double and single quantum well (QW)
structures at low temperatures. This luminescence appears as a ring around the
laser spot with the dark region between the spot and the ring. Developing the
theory of a free superflow of Bose-liquids we show that the macroscopic
luminesce rings and the dark state are signatures of the coherent superflow of
condensed excitons at temperatures below their Berezinskii-Kosterlitz-Thouless
(BKT) transition temperature. To further verify the dark excitonic superflow we
propose several keystone experiments, including interference of superflows from
two laser spots, vortex formation, scanning of moving dipole moments, and a
giant increase of the luminescence distance by applying one-dimensional
confinement potential. These experiments combined with our theory will open a
new avenue for creating and controlling superflow of coherent excitons on
nanoscale.
\\ ( http://arxiv.org/abs/1008.2778 , 124kb)
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arXiv:1008.2790
Date: Mon, 16 Aug 2010 23:05:04 GMT (516kb)
Title: Randomized benchmarking of atomic qubits in an optical lattice
Authors: S. Olmschenk, R. Chicireanu, K. D. Nelson, J. V. Porto
Categories: quant-ph
Comments: 10 pages, 4 figures
\\
We perform randomized benchmarking on neutral atomic quantum bits (qubits)
confined in an optical lattice. Single qubit gates are implemented using
microwaves, resulting in a measured error per randomized computational gate of
1.4(1) x 10^-4 that is dominated by the system T2 relaxation time. The results
demonstrate the robustness of the system, and its viability for more advanced
quantum information protocols.
\\ ( http://arxiv.org/abs/1008.2790 , 516kb)
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arXiv:1008.2884
Date: Tue, 17 Aug 2010 13:01:58 GMT (849kb,D)
Title: Comparison of 3 absolute gravimeters based on different methods for the
e-MASS project
Authors: A. Louchet-Chauvet, S. Merlet, Q. Bodart, A. Landragin, F. Pereira Dos
Santos, H. Baumann, G. D'Agostino and C. Origlia
Categories: physics.atom-ph
\\
We report on the comparison between three absolute gravimeters that took
place in April 2010 at Laboratoire National de M\'etrologie et d'Essais. The
three instruments (FG5#209 from METAS, Switzerland, IMGC-02 from INRIM, Italy,
and CAG from LNE-SYRTE, France) rely on different methods: optical and atomic
interferometry. We discuss their differences as well as their similarities. We
compare their measurements of the gravitational acceleration in 4 points of the
same pillar, in the perspective of an absolute determination of g for a watt
balance experiment
\\ ( http://arxiv.org/abs/1008.2884 , 849kb)
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arXiv:1008.2916 (*cross-listing*)
Date: Tue, 17 Aug 2010 15:23:00 GMT (563kb,D)
Title: The ground state of binary systems with a periodic modulation of the
linear coupling
Authors: Armand Niederberger and Boris A. Malomed and Maciej Lewenstein
Categories: quant-ph cond-mat.quant-gas
Comments: 8 pages, 3 figures
\\
We consider a quasi-one-dimensional two-component systm, described by a pair
of Nonlinear Schr\"{o}dinger/Gross-Pitaevskii Equations (NLSEs/GPEs), which are
coupled by the linear mixing, with local strength $\Omega $, and by the
nonlinear incoherent interaction. We assume the self-repulsive nonlinearity in
both components, and include effects of a harmonic trapping potential. The
model may be realized in terms of periodically modulated slab waveguides in
nonlinear optics, and in Bose-Einstein condensates too. Depending on the
strengths of the linear and nonlinear couplings between the components, the
ground states (GSs) in such binary systems may be symmetric or asymmetric. In
this work, we introduce a periodic spatial modulation of the linear coupling,
making $\Omega $ an odd, or even function of the coordinate. The sign flips of
$\Omega (x)$ strongly modify the structure of the GS in the binary system, as
the relative sign of its components tends to lock to the local sign of $\Omega
$. Using a systematic numerical analysis, and an analytical approximation, we
demonstrate that the GS of the trapped system contains one or several kinks
(dark solitons) in one component, while the other component does not change its
sign. Final results are presented in the form of maps showing the number of
kinks in the GS as a function of the system's parameters, with the odd/even
modulation function giving rise to the odd/even number of the kinks. The
modulation of $\Omega (x)$ also produces a strong effect on the transition
between states with nearly equal and strongly unequal amplitudes of the two
components.
\\ ( http://arxiv.org/abs/1008.2916 , 563kb)
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arXiv:1008.2922
Date: Tue, 17 Aug 2010 16:00:45 GMT (97kb,D)
Title: Universal Relations for Fermions with Large Scattering Length
Authors: Eric Braaten
Categories: cond-mat.quant-gas hep-ph nucl-th
Comments: 43 pages, 6 figures, to be published as a chapter in BCS-BEC
Crossover and the Unitary Fermi Gas (Lecture Notes in Physics), edited by W.
Zwerger (Springer, 2011)
\\
The behavior of fermions with two spin states that interact with a large
scattering length is constrained by universal relations that hold for any state
of the system. These relations involve a central property of the system called
the contact, which measures the number of pairs of fermions with different
spins that have small separations. The contact controls the thermodynamics of
the system as well as the large-momentum and high-frequency tails of
correlation functions. This review summarizes the current theoretical and
experimental status of these universal relations.
\\ ( http://arxiv.org/abs/1008.2922 , 97kb)
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arXiv:1008.2945
Date: Tue, 17 Aug 2010 18:06:34 GMT (617kb,D)
Title: Complete devil's staircase and crystal--superfluid transitions in a
dipolar XXZ spin chain: A trapped ion quantum simulation
Authors: Philipp Hauke, Fernando M. Cucchietti, Alexander M\"{u}ller-Hermes,
Mari-Carmen Ba\~{n}uls, J. Ignacio Cirac, Maciej Lewenstein
Categories: cond-mat.quant-gas
\\
Systems with long-range interactions show a variety of intriguing properties:
they typically accommodate many meta-stable states, they can give rise to
spontaneous formation of supersolids, and they can lead to counterintuitive
thermodynamic behavior. However, the increased complexity that comes with
long-range interactions strongly hinders theoretical studies. This makes a
quantum simulator for long-range models highly desirable. Here, we show that a
chain of trapped ions can be used to quantum simulate a one-dimensional model
of hard-core bosons with dipolar off-site interaction and tunneling, equivalent
to a dipolar XXZ spin-1/2 chain. We explore the rich phase diagram of this
model in detail, employing perturbative mean-field theory, exact
diagonalization, and quasiexact numerical techniques (density-matrix
renormalization group and infinite time evolving block decimation). We find
that the complete devil's staircase -- an infinite sequence of crystal states
existing at vanishing tunneling -- spreads to a succession of lobes similar to
the Mott-lobes found in Bose--Hubbard models. Investigating the melting of
these crystal states at increased tunneling, we do not find (contrary to
similar two-dimensional models) clear indications of supersolid behavior in the
region around the melting transition. However, we find that inside the
insulating lobes there are quasi-long range (algebraic) correlations, opposed
to models with nearest-neighbor tunneling which show exponential decay of
correlations.
\\ ( http://arxiv.org/abs/1008.2945 , 617kb)
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arXiv:1008.3000
Date: Wed, 18 Aug 2010 02:41:21 GMT (1098kb,D)
Title: Nonlinear magneto-optical rotation in the presence of radio-frequency
field
Authors: T. Zigdon, A. D. Wilson-Gordon, S. Guttikonda, E. J. Bahr, O. Neitzke,
S. M. Rochester, and D. Budker
Categories: physics.atom-ph
Comments: 14 pages, 7 figures. Associated media files hosted at
http://budker.berkeley.edu/rfnmor-movies/
\\
We report measurements of nonlinear magneto-optical rotation (NMOR) for the
D2 line of $^{87}$Rb atoms in an antirelaxation-coated vapor cell in the
presence of a radio-frequency (rf) field. The experimental NMOR signals as a
function of rf field frequency for various rf field powers are compared to a
theoretical model based on the density-matrix formalism. The comparison between
experiment and theory enables understanding of the ground-state atomic spin
polarization dynamics, illustrated using plots of the probability distribution
of the atomic angular momentum.
\\ ( http://arxiv.org/abs/1008.3000 , 1098kb)
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arXiv:1008.3004 (*cross-listing*)
Date: Wed, 18 Aug 2010 03:52:58 GMT (299kb)
Title: Modulation stabilization of Bloch oscillations of two-component
Bose-Einstein condensates in optical lattices
Authors: Huai-Qiang Gu, Jun-Hong An, and Kang Jin
Categories: cond-mat.quant-gas quant-ph
Comments: 13 pages in IOP preprint style, 5 figures
\\
We study the Bloch oscillations (BOs) of two-component Bose-Einstein
condensates (BECs) trapped in spin-dependent optical lattices. Based on the
derived equations of motion of the wave packet in the basis of localized wave
functions of the lattice sites, the damping effect induced by the
intercomponent and intracomponent interactions to the BOs is explored
analytically and numerically. We also show that such damping of the BOs can be
suppressed entirely if all the atom-atom interactions are modulated
synchronously and harmonically in time with suitable frequency via the Feshbach
resonance. When the intercomponent and the intracomponent interactions have
inverse signs, we find that the long-living BOs and even the revival of the BOs
can be achieved via only statically modulating the configuration of optical
lattices. The results provide a valuable guidance for achieving long-living BOs
in the two-component BEC system by the Feshbach resonances and manipulating the
configuration of the optical lattices.
\\ ( http://arxiv.org/abs/1008.3004 , 299kb)
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arXiv:1008.3050 (*cross-listing*)
Date: Wed, 18 Aug 2010 09:03:31 GMT (1642kb)
Title: Energy Spectra of Quantum Turbulence: Large-scale Simulation and
Modeling
Authors: Masahiko Machida, Narimasa Sasa, Takuma Kano, Victor S. L'vov, Oleksii
Rudenko, Makoto Tsubota
Categories: physics.flu-dyn physics.comp-ph
Comments: submitted to PRL: 4 pages, 2 figures
\\
In 2048^3 simulation of quantum turbulence within the Gross-Pitaevskii
equation we demonstrate that the large scale motions have a classical
Kolmogorov-1941 energy spectrum E(k) ~ k^{-5/3}, followed by an energy
accumulation with E(k) ~ const at 1/k about the mean intervortex distance. This
behavior was predicted by the L'vov-Nazarenko-Rudenko bottleneck model
[Phys.Rev.B 76, 024520 (2007)], further developed in the Letter.
\\ ( http://arxiv.org/abs/1008.3050 , 1642kb)
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arXiv:1008.3055
Date: Wed, 18 Aug 2010 09:27:15 GMT (368kb)
Title: Phase-separated Ferromagnetism in Spin-imbalanced Fermi Atoms Loaded on
an Optical Ladder: a DMRG study
Authors: M. Okumura, S. Yamada, M. Machida, H. Aoki
Categories: cond-mat.quant-gas
\\
We consider repulsively-interacting cold fermionic atoms loaded on an optical
ladder lattice in a trapping potential. The density-matrix
renormalization-group method is used to numerically calculate the ground state
for systematically varied values of interaction U and spin imbalance p in the
Hubbard model on the ladder. The system exhibits rich structures, where a fully
spin- polarized phase, spatially separated from other domains in the trapping
potential, appears for large enough U and p. The phase-separated ferromagnetism
can be captured as a real-space image of the energy gap between the
ferromagnetic and other states arising from a combined effect of Nagaoka's
ferromagnetism extended to the ladder [M. Kohno, Phys. Rev. B 56, 15015 (1997)]
and the density dependence of the energy separation between competing states.
We have also predicted how to maximize the ferromagnetic region.
\\ ( http://arxiv.org/abs/1008.3055 , 368kb)
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arXiv:1008.3057
Date: Wed, 18 Aug 2010 09:31:51 GMT (1733kb,D)
Title: Classical bifurcation at the transition from Rabi to Josephson dynamics
Authors: Tilman Zibold, Eike Nicklas, Christian Gross, Markus K. Oberthaler
Categories: cond-mat.quant-gas
\\
We report on the experimental realization of an internal bosonic Josephson
junction in a Rubidium spinor Bose-Einstein condensate. The measurement of the
full time dynamics in phase space allows the characterization of the
theoretically predicted $\pi$-phase modes and quantitatively confirms
analytical predictions, revealing a classical bifurcation. Our results suggest
that this system is a model system which can be tuned from classical to the
quantum regime and thus is an important step towards the experimental
investigation of entanglement generation close to critical points.
\\ ( http://arxiv.org/abs/1008.3057 , 1733kb)
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arXiv:1008.3058
Date: Wed, 18 Aug 2010 09:35:56 GMT (1003kb)
Title: From a single- to a double-well Penning trap
Authors: G. Ciaramicoli, I. Marzoli, and P. Tombesi
Categories: quant-ph physics.atom-ph
Comments: 4 pages, 7 figures
\\
The new generation of planar Penning traps promises to be a flexible and
versatile tool for quantum information studies. Here, we propose a fully
controllable and reversible way to change the typical trapping harmonic
potential into a double-well potential, in the axial direction. In this
configuration a trapped particle can perform coherent oscillations between the
two wells. The tunneling rate, which depends on the barrier height and width,
can be adjusted at will by varying the potential difference applied to the trap
electrodes. Most notably, tunneling rates in the range of kHz are achievable
even with a trap size of the order of 100 microns.
\\ ( http://arxiv.org/abs/1008.3058 , 1003kb)
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arXiv:1008.3191
Date: Thu, 19 Aug 2010 00:47:14 GMT (79kb)
Title: Trapped two-component Fermi gases with up to six particles: Energetics,
structural properties, and molecular condensate fraction
Authors: D. Blume and K. M. Daily
Categories: cond-mat.quant-gas
Comments: 20 pages, 14 figures
\\
We investigate small equal-mass two-component Fermi gases under external
spherically symmetric confinement in which atoms with opposite spins interact
through a short-range two-body model potential. We employ a non-perturbative
microscopic framework, the stochastic variational approach, and determine the
system properties as functions of the interspecies s-wave scattering length a,
the orbital angular momentum L of the system, and the numbers N1 and N2 of
spin-up and spin-down atoms (with N1-N2 =0 or 1 and N < 7, where N=N1+N2). At
unitarity, we determine the energies of the five- and six-particle systems for
various ranges r0 of the underlying two-body model potential and extrapolate to
the zero-range limit. These energies serve as benchmark results that can be
used to validate and assess other numerical approaches. We also present
structural properties such as the pair distribution function and the radial
density. Furthermore, we analyze the one-body and two-body density matrices. A
measure for the molecular condensate fraction is proposed and applied. Our
calculations show explicitly that the natural orbitals and the momentum
distributions of atomic Fermi gases approach those characteristic for a
molecular Bose gas if the s-wave scattering length a, a>0, is sufficiently
small.
\\ ( http://arxiv.org/abs/1008.3191 , 79kb)
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arXiv:1008.3212 (*cross-listing*)
Date: Thu, 19 Aug 2010 04:43:57 GMT (163kb)
Title: Leggett's Collective Modes in Multiband Superfluids and Superconductors:
Multiple Dynamical Classes
Authors: Yukihiro Ota, Masahiko Machida, Tomio Koyama, Hideo Aoki
Categories: cond-mat.supr-con cond-mat.str-el quant-ph
Comments: 5 pages, 3 figures
\\
One important way to characterize the states having a gauge symmetry
spontaneously broken over multibands should be to look at their collective
excitation modes. While for two-band superfluids and superconductors Leggett's
1966 analysis shows that a massive, out-of-phase collective mode coexists with
the Nambu-Goldstone mode, here we have posed a question: are there features
specific to superconductors (superfluids) having three or more bands. We find
that a three-band system has {\it multiple Leggett modes} with significantly
different masses, which can be classified into different dynamical classes
according to whether multiple inter-band Josephson currents add or cancel. This
provides a way to dynamically characterize multiband superconductivity while
the pairing symmetry is a static property.
\\ ( http://arxiv.org/abs/1008.3212 , 163kb)
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arXiv:1008.3224
Date: Thu, 19 Aug 2010 06:28:43 GMT (244kb)
Title: Atomic fountain of laser-cooled Yb atoms for precision measurements
Authors: Kanhaiya Pandey, K. D. Rathod, Alok K. Singh, and Vasant Natarajan
Categories: physics.atom-ph physics.optics
Comments: 6 pages, 7 figures
\\
We demonstrate launching of laser-cooled Yb atoms in a cold atomic fountain.
Atoms in a collimated thermal beam are first cooled and captured in a
magneto-optic trap (MOT) operating on the strongly-allowed ${^1S}_0 \rightarrow
{^1P}_1$ transition at 399~nm (blue line). They are then transferred to a MOT
on the weakly-allowed ${^1S}_0 \rightarrow {^3P}_1$ transition at 556~nm (green
line). Cold atoms from the green MOT are launched against gravity at a velocity
of around 2.5~m/s using a pair of green beams. We trap more than $10^7$ atoms
in the blue MOT and transfer up to 70\% into the green MOT. The temperature for
the odd isotope, $^{171}$Yb, is $\sim$1~mK in the blue MOT, and reduces by a
factor of 40 in the green MOT.
\\ ( http://arxiv.org/abs/1008.3224 , 244kb)
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arXiv:1008.3227
Date: Thu, 19 Aug 2010 06:48:06 GMT (153kb)
Title: Role of population transfer under strong probe conditions in
electromagnetically induced transparency
Authors: Kanhaiya Pandey, Dipankar Kaundilya, and Vasant Natarajan
Categories: physics.optics physics.atom-ph
Comments: 4 pages, 4 figure, accepted in Optics Communications
\\
We analyze theoretically the phenomenon of electromagnetically induced
transparency (EIT) under conditions where the probe laser is not in the usual
weak limit. We consider the effects in both three-level and four-level systems,
which are either closed or open (due to losses to an external metastable
level). We find that the EIT dip almost disappears in a closed three-level
system but survives in an open system. In four-level systems, there is a narrow
enhanced-absorption peak (EITA) at line center, which has applications as an
optical clock. The peak converts to an EIT dip in a closed system, but again
survives in an open system.
\\ ( http://arxiv.org/abs/1008.3227 , 153kb)
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\\
arXiv:1008.3228
Date: Thu, 19 Aug 2010 06:58:23 GMT (29kb)
Title: Precise measurement of hyperfine structure in the ${2P}_{1/2}$ state of
$^{7}$Li using saturated-absorption spectroscopy
Authors: Alok K. Singh, Lal Muanzuala, and Vasant Natarajan
Categories: physics.atom-ph physics.optics
Comments: 5 pages, 3 figures
\\
We report a precise measurement of the hyperfine interval in the ${2P}_{1/2}$
state of $^{7}$Li. The transition from the ground state ($D_1$ line) is
accessed using a diode laser and the technique of saturated-absorption
spectroscopy in hot Li vapor. The interval is measured by locking an
acousto-optic modulator to the frequency difference between the two hyperfine
peaks. The measured interval of 92.040(6)~MHz is consistent with an earlier
measurement reported by us using an atomic-beam spectrometer [Das and
Natarajan, J.\ Phys.\ B {\bf 41}, 035001 (2008)]. The interval yields the
magnetic dipole constant in the $P_{1/2}$ state as $A=46.047(3)$, which is
discrepant from theoretical calculations by $>80$~kHz.
\\ ( http://arxiv.org/abs/1008.3228 , 29kb)
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\\
arXiv:1008.3264
Date: Thu, 19 Aug 2010 10:32:00 GMT (363kb)
Title: Interlayer superfluidity in bilayer systems of fermionic polar molecules
Authors: A. Pikovski, M. Klawunn, G.V. Shlyapnikov, and L. Santos
Categories: cond-mat.quant-gas
Comments: 4 pages
\\
We consider fermionic polar molecules in a bilayer geometry where they are
oriented perpendicularly to the layers, which permits both low inelastic losses
and superfluid pairing. The dipole-dipole interaction between molecules of
different layers leads to the emergence of interlayer superfluids. The
superfluid regimes range from BCS-like fermionic superfluidity with a high
$T_c$ to (quasi)BEC of interlayer dimers, thus exhibiting a peculiar BCS-BEC
crossover. We show that one can cover the entire crossover regime under current
experimental conditions.
\\ ( http://arxiv.org/abs/1008.3264 , 363kb)
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\\
arXiv:1008.3277
Date: Thu, 19 Aug 2010 11:47:23 GMT (39kb)
Title: Statistical properties of one dimensional Bose gas
Authors: Przemyslaw Bienias, Krzysztof Pawlowski, Mariusz Gajda, Kazimierz
Rzazewski
Categories: quant-ph cond-mat.quant-gas
\\
Monte Carlo method within, so called, classical fields approximation is
applied to one dimensional weakly interacting repulsive Bose gas trapped in a
harmonic potential. Equilibrium statistical properties of the condensate are
calculated within a canonical ensemble. We also calculate experimentally
relevant low order correlation functions of the whole gas.
\\ ( http://arxiv.org/abs/1008.3277 , 39kb)
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\\
arXiv:1008.3294
Date: Thu, 19 Aug 2010 13:19:39 GMT (341kb)
Title: Localization of a dipolar Bose-Einstein condensate in a bichromatic
optical lattice
Authors: P. Muruganandam, R. Kishor Kumar, S. K. Adhikari
Categories: cond-mat.quant-gas
\\
By numerical simulation and variational analysis of the Gross-Pitaevskii
equation we study the localization, with an exponential tail, of a dipolar
Bose-Einstein condensate (DBEC) of $^{52}$Cr atoms in a three-dimensional
bichromatic optical-lattice (OL) generated by two monochromatic OL of
incommensurate wavelengths along three orthogonal directions. For a fixed
dipole-dipole interaction, a localized state of a small number of atoms ($\sim
1000$) could be obtained when the short-range interaction is not too attractive
or not too repulsive. A phase diagram showing the region of stability of a DBEC
with short-range interaction and dipole-dipole interaction is given.
\\ ( http://arxiv.org/abs/1008.3294 , 341kb)
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\\
arXiv:1008.3302 (*cross-listing*)
Date: Thu, 19 Aug 2010 14:00:51 GMT (160kb)
Title: Co--propagating Bose--Einstein Condensates and electromagnetic
radiation: Emission of mutually localized structures
Authors: Arkady Kim, Federica Cattani, Dan Anderson and Mietek Lisak
Categories: nlin.PS physics.atom-ph physics.optics
Comments: 7 pages, 10 figures manuscript to be submitted to PRA
\\
Using a semi-classical model to describe the interaction between coherent
electromagnetic radiation and a Bose-Einstein condensate in the limit of zero
temperature, including the back action of the atoms on the radiation, we have
analyzed the phenomenon of emission of solitary-like wave packets which can
accompany the formation of mutually localized atom-laser structures.
\\ ( http://arxiv.org/abs/1008.3302 , 160kb)
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\\
arXiv:1008.3348
Date: Thu, 19 Aug 2010 16:58:07 GMT (413kb)
Title: Thermodynamics of balanced and slightly spin-imbalanced Fermi gases at
unitarity
Authors: Olga Goulko and Matthew Wingate
Categories: cond-mat.quant-gas
Report-no: DAMTP-2010-62
\\
In this paper we present a Monte Carlo calculation of the critical
temperature and other thermodynamic quantities for the unitary Fermi gas with a
population imbalance (unequal number of fermions in the two spin components).
We describe an improved worm type algorithm that is less prone to
autocorrelations than the previously available methods and show how this
algorithm can be applied to simulate the unitary Fermi gas in presence of a
small imbalance. Our data indicates that the critical temperature remains
almost constant for small imbalances $h=\Delta\mu/\varepsilon_F\lessapprox0.2$.
We obtain the continuum result $T_c=0.171(5)\varepsilon_F$ in units of Fermi
energy and derive a lower bound on the deviation of the critical temperature
from the balanced limit, $T''_c(h)>-0.5\varepsilon_F$. Using an additional
assumption a tighter lower bound can be obtained. We also measure the energy
per particle and the chemical potential in the balanced and imbalanced cases.
\\ ( http://arxiv.org/abs/1008.3348 , 413kb)
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The replacements:
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\\
arXiv:1005.3660 (*cross-listing*)
replaced with revised version Thu, 12 Aug 2010 20:50:37 GMT (165kb)
Title: Lieb-Liniger gas in a constant force potential
Authors: D. Juki\'c, S. Gali\'c, R. Pezer, H. Buljan
Categories: cond-mat.quant-gas quant-ph
Journal-ref: Phys. Rev. A 82, 023606 (2010)
DOI: 10.1103/PhysRevA.82.023606
\\ ( http://arxiv.org/abs/1005.3660 , 165kb)
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\\
arXiv:1007.0281 (*cross-listing*)
replaced with revised version Fri, 13 Aug 2010 03:01:56 GMT (2163kb)
Title: Phase fluctuations in anisotropic Bose condensates: from cigars to rings
Authors: L. Mathey, A. Ramanathan, K. C. Wright, S. R. Muniz, W. D. Phillips
and Charles W. Clark
Categories: cond-mat.quant-gas quant-ph
Comments: 9 pages, 5 figures, minor edits
\\ ( http://arxiv.org/abs/1007.0281 , 2163kb)
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\\
arXiv:0901.3084
replaced with revised version Fri, 13 Aug 2010 12:08:52 GMT (24kb)
Title: Atomic multipole relaxation rates near surfaces
Authors: J. A. Crosse and Stefan Scheel
Categories: quant-ph
Comments: Updated to journal version. 16 pages
Journal-ref: Phys. Rev. A, 79, 062902 (2009)
DOI: 10.1103/PhysRevA.79.062902
\\ ( http://arxiv.org/abs/0901.3084 , 24kb)
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\\
arXiv:1008.2096 (*cross-listing*)
replaced with revised version Fri, 13 Aug 2010 14:16:00 GMT (228kb)
Title: Dynamic localization of cold atoms in driven lattices: an overlooked
phase
Authors: K. Kudo and T.S. Monteiro
Categories: cond-mat.quant-gas quant-ph
Comments: 5 pages, 2 figures
\\ ( http://arxiv.org/abs/1008.2096 , 228kb)
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\\
arXiv:0905.2100
replaced with revised version Sun, 15 Aug 2010 10:36:00 GMT (0kb,I)
Title: Exciting the Scissors Mode in crystals with strong spin-orbit coupling
as in Bose-Einstein Condensates
Authors: Keisuke Hatada, Kuniko Hayakawa, Fabrizio Palumbo
Categories: cond-mat.str-el cond-mat.quant-gas
Comments: This paper has been withdrawn by the authors. It is replaced by
arXiv:1004.2220
\\ ( http://arxiv.org/abs/0905.2100 , 0kb)
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\\
arXiv:1005.4213
replaced with revised version Sun, 15 Aug 2010 15:56:52 GMT (320kb)
Title: Cold matter trapping via rotating helical optical potential
Authors: A.Yu.Okulov
Categories: physics.atom-ph cond-mat.quant-gas nlin.PS physics.optics
Comments: 7 pages, 3 figures, submitted to referred journal
\\ ( http://arxiv.org/abs/1005.4213 , 320kb)
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\\
arXiv:1006.5148
replaced with revised version Mon, 16 Aug 2010 12:38:19 GMT (1474kb,D)
Title: Spin-Orbit Coupled Spinor Bose-Einstein Condensates
Authors: Chunji Wang, Chao Gao, Chao-Ming Jian and Hui Zhai
Categories: cond-mat.quant-gas cond-mat.str-el
Comments: 5 pages, 4 figures, revised thanks to referee's comments
\\ ( http://arxiv.org/abs/1006.5148 , 1474kb)
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\\
arXiv:1003.2798
replaced with revised version Tue, 17 Aug 2010 05:10:05 GMT (689kb)
Title: Hidden vortices in a Bose-Einstein condensate in a rotating double-well
potential
Authors: Linghua Wen, Hongwei Xiong, and Biao Wu
Categories: cond-mat.quant-gas cond-mat.stat-mech
Comments: 6pages,5figures
\\ ( http://arxiv.org/abs/1003.2798 , 689kb)
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\\
arXiv:1004.2203
replaced with revised version Tue, 17 Aug 2010 10:31:05 GMT (758kb)
Title: Statistical properties of the spectrum the extended Bose-Hubbard model
Authors: Corinna Kollath, Guillaume Roux, Giulio Biroli, Andreas Laeuchli
Categories: cond-mat.quant-gas
Comments: 18 pages, 15 figures
Journal-ref: J. Stat. Mech. (2010) P08011
DOI: 10.1088/1742-5468/2010/08/P08011
\\ ( http://arxiv.org/abs/1004.2203 , 758kb)
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\\
arXiv:1005.3846 (*cross-listing*)
replaced with revised version Tue, 17 Aug 2010 19:14:55 GMT (837kb)
Title: Cold heteronuclear atom-ion collisions
Authors: Christoph Zipkes, Stefan Palzer, Lothar Ratschbacher, Carlo Sias,
Michael K\"ohl
Categories: physics.atom-ph cond-mat.quant-gas quant-ph
\\ ( http://arxiv.org/abs/1005.3846 , 837kb)
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\\
arXiv:1002.3304
replaced with revised version Tue, 17 Aug 2010 19:15:57 GMT (781kb)
Title: A trapped single ion inside a Bose-Einstein condensate
Authors: Christoph Zipkes, Stefan Palzer, Carlo Sias, and Michael K\"ohl
Categories: cond-mat.quant-gas cond-mat.other physics.atom-ph quant-ph
Journal-ref: Nature 464, 388 (2010)
DOI: 10.1038/nature08865
\\ ( http://arxiv.org/abs/1002.3304 , 781kb)
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\\
arXiv:0909.4990
replaced with revised version Wed, 18 Aug 2010 05:03:11 GMT (15kb)
Title: Entangled Superfluids
Authors: Yu Shi
Categories: cond-mat.quant-gas
Comments: 10 pages. Published in PRA
Journal-ref: Phys. Rev. A 82, 013637 (2010)
\\ ( http://arxiv.org/abs/0909.4990 , 15kb)
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\\
arXiv:1007.1898
replaced with revised version Wed, 18 Aug 2010 09:25:05 GMT (3806kb)
Title: Vibrational stabilization of ultracold KRb molecules. A comparative
study
Authors: Mamadou Ndong and Christiane P. Koch
Categories: physics.atom-ph
Comments: Text and figures slightly modified
\\ ( http://arxiv.org/abs/1007.1898 , 3806kb)
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\\
arXiv:0711.0064
replaced with revised version Thu, 19 Aug 2010 06:34:02 GMT (190kb)
Title: Subnatural linewidth using electromagnetically induced transparency in
Doppler-broadened vapor
Authors: S. M. Iftiquar, G. R. Karve, and Vasant Natarajan
Categories: physics.atom-ph physics.optics
Comments: 6 pages, 7 figures
Journal-ref: Physical Review A 77, 063807 (2008)
DOI: 10.1103/PhysRevA.77.063807
\\ ( http://arxiv.org/abs/0711.0064 , 190kb)
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\\
arXiv:0711.0067
replaced with revised version Thu, 19 Aug 2010 06:38:18 GMT (163kb)
Title: High-precision measurement of hyperfine structure in the $D$ lines of
alkali atoms
Authors: Dipankar Das and Vasant Natarajan
Categories: physics.atom-ph
Comments: 24 pages, 13 figures, accepted in Journal of Physics B: Atomic,
Molecular and Optical Physics
Journal-ref: J. Phys. B: At. Mol. Opt. Phys. 40 (2008) 035001 (12pp)
DOI: 10.1088/0953-4075/41/3/035001
\\ ( http://arxiv.org/abs/0711.0067 , 163kb)
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Till next time,
Matt.
--
=========================================================================
Dr M. J. Davis, Associate Professor in Physics
School of Mathematics and Physics, ph : +61 7 334 69824
The University of Queensland, fax : +61 7 336 51242
Brisbane, QLD 4072, mdavis_at_physics.uq.edu.au
Australia. www.physics.uq.edu.au/people/mdavis/
=========================================================================
Matt's arXiv selection: weekly summary of cold-atom papers from arXiv.org
http://www.physics.uq.edu.au/people/mdavis/matts_arXiv/
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