From: Matthew Davis <mdavis_at_physics.uq.edu.au>

Date: Thu, 21 Oct 2010 22:55:48 +1000

Date: Thu, 21 Oct 2010 22:55:48 +1000

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/ ========================================================================= Legal stuff: Unless stated otherwise, this e-mail represents only the views of the sender and not the views of the University of Queensland ========================================================================= _______________________________________________ Matts-arxiv mailing list Matts-arxiv_at_lists.sps.uq.edu.auReceived on Thu Nov 04 2010 - 10:05:08 EST

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