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

Date: Mon, 15 Jun 2009 14:25:22 +1000

Date: Mon, 15 Jun 2009 14:25:22 +1000

Dear subscribers,

Andy Ferris has compiled this week's mailing. It has 30 new preprints and 11

replacements:

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arXiv:0905.0052

Date: Fri, 1 May 2009 06:10:07 GMT (359kb)

Title: Optimised control of Stark-shift-chirped rapid-adiabatic-passage in a

lambda-type three-level system

Authors: Johann-Heinrich Sch\"onfeldt, Jason Twamley, Stojan Rebi\'c

Categories: quant-ph

Comments: 6 pages, 6 figures, 1 table

\\

Inhomogeneous broadening of energy levels is one of the principal limiting

factors for achieving "slow" or "stationary" light in solid state media by

means of electromagnetically induced transparency (EIT), a quantum version of

stimulated Raman adiabatic passage (STIRAP). Stark-shift-chirped

rapid-adiabatic-passage (SCRAP) has been shown to be far less sensitive to

inhomogeneous broadening than STIRAP, a population transfer technique to which

it is closely related. We further optimise the pulses used in SCRAP to be even

less sensitive to inhomogeneous broadening in a lambda-type three-level system.

The optimised pulses perform at a higher fidelity than the standard gaussian

pulses for a wide range of detunings (i.e. large inhomogeneous broadening).

\\ ( http://arxiv.org/abs/0905.0052 , 359kb)

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arXiv:0905.0093

Date: Fri, 1 May 2009 14:03:14 GMT (117kb)

Title: Extended solutions via the trial-orbit method for two-field models

Authors: A. R. Gomes, D. Bazeia

Categories: physics.optics

Comments: 14 pages, 4 figures

Journal-ref: Phys. Scr. 79 (2009) 055005

DOI: 10.1088/0031-8949/79/05/055005

\\

In this work we investigate the presence of defect structures in models

described by two real scalar fields. The coupling between the two fields is

inspired on the equations for a multimode laser, and the minimum energy trivial

configurations are shown to be structurely dependent on the parameters of the

models. The trial orbit method is then used and several non-trivial analytical

solutions corresponding to topological solitons are obtained.

\\ ( http://arxiv.org/abs/0905.0093 , 117kb)

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arXiv:0905.0111

Date: Fri, 1 May 2009 16:13:21 GMT (227kb)

Title: On the Burgers vector of a wave dislocation

Authors: Mark R. Dennis

Categories: physics.optics

Comments: 15 pages, 4 figures, IoP style

\\

Following Nye and Berry's analogy with crystal dislocations, an approach to

the Burgers vector of a wave dislocation (phase singularity, optical vortex) is

proposed. It is defined to be a regularized phase gradient evaluated at the

phase singularity, and is computed explicitly. The screw component of this

vector is naturally related to the helicoidal twisting of wavefronts along a

vortex line, and is related to the helicity of the phase gradient. The edge

component is related to the nearby current flow (defined by the phase gradient)

perpendicular to the vortex, and the distribution of this component is found

numerically for random two-dimensional monochromatic waves.

\\ ( http://arxiv.org/abs/0905.0111 , 227kb)

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arXiv:0905.0158

Date: Fri, 1 May 2009 23:12:14 GMT (338kb)

Title: Is state tomography an unambiguous test of quantum entanglement?

Authors: Niels Gr{\o}nbech-Jensen and Jeffrey E. Marchese and Matteo Cirillo

and James A. Blackburn

Categories: cond-mat.supr-con cond-mat.stat-mech

Comments: Four pages, two figures

\\

We provide an alternative interpretation of recently published experimental

results that were represented as demonstrating entanglement between two

macroscopic quantum Josephson oscillators. We model the experimental system

using the well-established classical equivalent circuit of a resistively and

capacitively shunted junction. Simulation results are used to generate the

corresponding density matrix, which is strikingly similar to the previously

published matrix that has been declared to be an unambiguous demonstration of

quantum entanglement. Since our data are generated by a classical model, we

therefore submit that state tomography cannot be used to determine absolutely

whether or not quantum entanglement has taken place. Analytical arguments are

given for why the classical analysis provides an adequate explanation of the

experimental results.

\\ ( http://arxiv.org/abs/0905.0158 , 338kb)

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arXiv:0905.0222

Date: Sat, 2 May 2009 17:41:42 GMT (9kb)

Title: Pairing, off-diagonal long-range order, and quantum phase transition in

strongly attracting ultracold Bose gas mixtures in tight waveguides

Authors: M.D. Girardeau

Categories: cond-mat.quant-gas cond-mat.other

Comments: 4 pages, no figures, revtex4. Submitted to PRL

\\

A model of two 1D ideal Bose gases A and B with strong AB attractions induced

by a p-wave AB Feshbach resonance is studied. The model is solved exactly by a

Bose-Bose duality mapping, and it is shown that there is no A-component or

B-component Bose-Einstein condensation and no AB-pair off-diagonal long-range

order (ODLRO), but both AA-pair and BB-pair ODLRO. After generalization by

adding even-wave AA and BB repulsion and reducing the strength of the odd-wave

AB attraction by Feshbach resonance detuning, a quantum phase transition occurs

between a phase with AB contact nodes and one with no such nodes.

\\ ( http://arxiv.org/abs/0905.0222 , 9kb)

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arXiv:0905.0257

Date: Sun, 3 May 2009 11:52:07 GMT (131kb)

Title: Hybridization and excitation of second sound in a trapped Fermi gas at

unitarity

Authors: E. Taylor, H. Hu, X.-J. Liu, L. P. Pitaevskii, A. Griffin, S.

Stringari

Categories: cond-mat.quant-gas

Comments: 4 pages, 2 figures

\\

Using a variational approach, we solve the equations of two-fluid

hydrodynamics in a unitary Fermi gas trapped by a harmonic potential. We show

that the in-phase density oscillations (first sound) weakly couple to

out-of-phase entropy oscillations (second sound) of the system, giving rise to

a typical hybridization effect where the frequencies cross. We predict the

value of the frequency splitting caused by hybridization and show how the

coupling results in a beating effect in the density response. This gives a

promising way of exciting and detecting second sound in this system.

\\ ( http://arxiv.org/abs/0905.0257 , 131kb)

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arXiv:0905.0343

Date: Mon, 4 May 2009 10:10:12 GMT (229kb)

Title: The role of spatial inhomogeneity in dissociation of trapped molecular

condensates

Authors: Magnus Ogren and K. V. Kheruntsyan

Categories: cond-mat.quant-gas

Comments: 18 pages, 10 figures

\\

We theoretically analyze dissociation of a harmonically trapped Bose-Einstein

condensate of molecular dimers and examine how the spatial inhomogeneity of the

molecular condensate affects the conversion dynamics and the atom-atom pair

correlations in the short-time limit. Both fermionic and bosonic statistics of

the constituent atoms are considered. Using the undepleted molecular field

approximation, we obtain explicit analytic results for the asymptotic behavior

of the second-order correlation functions and relative number squeezing between

the dissociated atoms in one, two and three spatial dimensions. Comparison with

the numerical results shows that the analytic approach employed here captures

the main underlying physics and provides useful insights into the dynamics of

dissociation for conversion efficiencies less than 10%. The results show

explicitly how the strength of atom-atom correlations and relative number

squeezing degrade with a decrease of the size of the molecular condensate.

\\ ( http://arxiv.org/abs/0905.0343 , 229kb)

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arXiv:0905.0386

Date: Mon, 4 May 2009 09:23:47 GMT (4173kb)

Title: The physics of dipolar bosonic quantum gases

Authors: T Lahaye, C Menotti, L Santos, M Lewenstein and T Pfau

Categories: cond-mat.quant-gas

Comments: Review article, 71 pages, 35 figures, 350 references. Submitted to

Reports on Progress in Physics

\\

This article reviews the recent theoretical and experimental advances in the

study of ultracold gases made of bosonic particles interacting via the

long-range, anisotropic dipole-dipole interaction, in addition to the

short-range and isotropic contact interaction usually at work in ultracold

gases. The specific properties emerging from the dipolar interaction are

emphasized, from the mean-field regime valid for dilute Bose-Einstein

condensates, to the strongly correlated regimes reached for dipolar bosons in

optical lattices.

\\ ( http://arxiv.org/abs/0905.0386 , 4173kb)

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arXiv:0905.0448

Date: Mon, 4 May 2009 18:22:54 GMT (408kb,D)

Title: Three-body Casimir effects and non-monotonic forces

Authors: P. Rodriguez-Lopez, S. J. Rahi, T. Emig

Categories: cond-mat.stat-mech

Comments: 4 pages, 4 figures

\\

Casimir interactions are not pair-wise additive. This property leads to

collective effects that we study for a pair of objects near a conducting wall.

We employ a scattering approach to compute the interaction in terms of

fluctuating multipoles. The wall can lead to a non-monotonic force between the

objects. For two atoms with anisotropic electric and magnetic dipole

polarizabilities we demonstrate that this non-monotonic effect results from a

competition between two- and three body interactions. By including higher order

multipoles we obtain the force between two macroscopic metallic spheres for a

wide range of sphere separations and distances to the wall.

\\ ( http://arxiv.org/abs/0905.0448 , 408kb)

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arXiv:0905.0151

Date: Fri, 1 May 2009 21:12:31 GMT (15kb)

Title: Creating and observing N-partite entanglement with atoms

Authors: Mark S. Everitt, Martin L. Jones, Benjamin T. H. Varcoe, Jacob A.

Dunningham

Categories: quant-ph

Comments: 4 pages, 1 figure

\\

The Mermin inequality provides a criterion for experimentally ruling out

local-realistic descriptions of multiparticle systems. A violation of this

inequality means that the particles must be entangled, but does not, in

general, indicate whether N-partite entanglement is present. For this, a

stricter bound is required. Here we discuss this bound and use it to propose a

scheme for demonstrating N-partite entanglement with Rydberg atoms in microwave

cavities.

\\ ( http://arxiv.org/abs/0905.0151 , 15kb)

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arXiv:0905.0159

Date: Fri, 1 May 2009 22:43:40 GMT (1572kb,D)

Title: Superfluid turbulence from quantum Kelvin wave to classical Kolmogorov

cascades

Authors: Jeffrey Yepez

Categories: quant-ph

Comments: 4 pages, 2 figures

\\

A novel unitary quantum lattice gas algorithm is used to simulate quantum

turbulence of a BEC described by the Gross-Pitaevskii equation on grids up to

57603. For the first time, an accurate power law scaling for the quantum

Kelvin wave cascade is determined: k^{-3}. The incompressible kinetic energy

spectrum exhibits very distinct power law spectra in 3 ranges of k-space: a

classical Kolmogorov k^{-5/3} spectrum at scales much greater than the

individual quantum vortex cores, and a quantum Kelvin wave cascade spectrum

k^{-3} on scales of order the vortex cores. In the semiclassical regime between

these two spectra there is a pronounced steeper spectral decay, with

non-universal exponent. The Kelvin k^{-3} spectrum is very robust, even on

small grids, while the Kolmogorov k^{-5/3} spectrum becomes more and more

apparent as the grids increase from 20483 grids to 57603.

\\ ( http://arxiv.org/abs/0905.0159 , 1572kb)

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arXiv:0905.0286

Date: Sun, 3 May 2009 20:14:33 GMT (966kb,D)

Title: Suppression of collisional decoherence

Authors: Yoav Sagi, Ido Almog and Nir Davidson

Categories: quant-ph

Comments: 4 pages, 5 figures

\\

High density ensembles of cold atoms can be used as quantum memory devices,

but often suffer from {a} high collision rate that leads to rapid decoherence.

We present a novel method to suppress this decoherence mechanism using a

continuous strong echo pulse, achieving a thirty-fold increase in the coherence

time of cold 87Rb atoms trapped in a dipole trap. Coherence times of more than

100ms are demonstrated for an ensemble with OD>100.

\\ ( http://arxiv.org/abs/0905.0286 , 966kb)

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arXiv:0905.0378

Date: Sat, 25 Apr 2009 00:58:37 GMT (1674kb,D)

Title: Invisibility of quantum systems to tunneling of matter waves

Authors: Sergio Cordero and Gaston Garcia-Calderon

Categories: quant-ph

\\

We show that an appropriate choice of the potential parameters in

one-dimensional quantum systems allows for unity transmission of the tunneling

particle at all incident tunneling energies, except at controllable exceedingly

small incident energies. The corresponding dwell time and the transmission

amplitude are indistinguishable from those of a free particle in the

unity-transmission regime. This implies the possibility of designing quantum

systems that are invisible to tunneling by a passing wave packet.

\\ ( http://arxiv.org/abs/0905.0378 , 1674kb)

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arXiv:0905.0426

Date: Mon, 4 May 2009 17:05:30 GMT (33kb)

Title: The most generalized analytical approximation to the solution of

single-mode spin-boson model without rotating-wave approximation

Authors: T. Liu, K. L. Wang, and M. Feng

Categories: quant-ph

Comments: 3 figures

\\

The single-mode spin-boson model (SMSBM) has extensive application in

different subfields of physics. In the absence of rotating-wave approximation

(RWA), we try to solve SMSBM analytically. We argue that the analytical

expression obtained is the most exact approximation to the solution of the

system under the assumption of Abel-Ruffini theorem, which works for a wide

range of the parameters such as coupling strength and detuning and would be

practical for currently available experiments.

\\ ( http://arxiv.org/abs/0905.0426 , 33kb)

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arXiv:0905.0601

Date: Tue, 5 May 2009 13:22:13 GMT (49kb)

Title: Superradiant and Dark Exciton States in an Optical Lattice within a

Cavity

Authors: Hashem Zoubi, and Helmut Ritsch

Categories: quant-ph

Comments: 4 pages, 11 figures

\\

We study ultracold atoms in a finite size one-dimensional optical lattice

prepared in the Mott insulator phase and commonly coupled to a single cavity

mode. Due to resonance dipole-dipole interactions among the atoms, electronic

excitations delocalize and form {\it excitons}. These exciton modes are divided

into two groups: antisymmetric modes which decouple from the cavity mode

forming {\it dark states}, and symmetric modes significantly coupled to the

cavity mode called {\it bright states}. In typical setups the lowest and most

symmetric exciton is coupled to the cavity photons much stronger than the other

bright states and dominates the optical properties response of the atoms ({\it

superradiant state}). In the strong coupling regime this superradiant state is

coherently mixed with the cavity photon to form a doublet of polariton states

with the Rabi splitting.

\\ ( http://arxiv.org/abs/0905.0601 , 49kb)

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arXiv:0905.0711

Date: Tue, 5 May 2009 21:47:56 GMT (346kb)

Title: Quantum dynamics of cavity assisted photoassociation of Bose-Einstein

condensed atoms

Authors: Christopher P. Search, J. Mauricio Campuzano, and Marko Zivkovic

Categories: cond-mat.quant-gas

\\

We explore the quantum dynamics of photoassociation of Bose-Einstein

condensed atoms into molecules using an optical cavity field. Inside of an

optical resonator, photoassociation of quantum degenerate atoms involves the

interaction of three coupled quantum fields for the atoms, molecules, and the

photons. The feedback created by a high-Q optical cavity causes the cavity

field to become a dynamical quantity whose behavior is linked in a nonlinear

manner to the atoms inside and where vacuum fluctuations have a more important

role than in free space. We develop and compare several methods for calculating

the dynamics of the atom-molecule conversion process with a coherently driven

cavity field. We first introduce an alternate operator representation for the

Hamiltonian from which we derive an improved form of mean field theory and an

approximate solution of the Heisenberg-Langevin (HL) equations that properly

accounts for quantum noise in the cavity field. It is shown that our improved

mean field theory corrects several deficiencies in traditional mean field

theory based on expectation values of annihilation/creation operators. Also, we

show by direct comparison to numerical solutions of the density matrix

equations that our approximate quantum solution of HL equations gives an

accurate description of weakly or undriven cavities where mean field theories

break down.

\\ ( http://arxiv.org/abs/0905.0711 , 346kb)

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arXiv:0905.0817

Date: Wed, 6 May 2009 12:21:25 GMT (6kb)

Title: Probing superfluidity of periodically trapped ultracold atoms in a

cavity by transmission spectroscopy

Authors: Aranya B.Bhattacherjee, Tarun Kumar and ManMohan

Categories: cond-mat.quant-gas quant-ph

Comments: 3 pages

\\

We study a system of periodic Bose condensed atoms coupled to cavity photons

using the input-output formalism. We show that the cavity will either act as a

through pass Lorentzian filter when the superfluid fraction of the condensate

is minimum or completely reflect the input field when the superfluid fraction

is maximum. We show that by monitoring the ratio between the transmitted field

and the reflected field, one can estimate the superfluid fraction.

\\ ( http://arxiv.org/abs/0905.0817 , 6kb)

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arXiv:0905.0824

Date: Wed, 6 May 2009 13:31:06 GMT (752kb)

Title: Probing quasi-particle states in strongly interacting atomic gases by

momentum-resolved Raman photoemission spectroscopy

Authors: Tung-Lam Dao, Iacopo Carusotto and Antoine Georges

Categories: cond-mat.quant-gas cond-mat.str-el

Comments: 10 pages, 10 figures

\\

We investigate a momentum-resolved Raman spectroscopy technique which is able

to probe the one-body spectral function and the quasi-particle states of a gas

of strongly interacting ultracold atoms. This technique is inspired by

Angle-Resolved Photo-Emission Spectroscopy, a powerful experimental probe of

electronic states in solid-state systems. Quantitative examples of

experimentally accessible spectra are given for the most significant regimes

along the BEC-BCS crossover. When the theory is specialized to RF spectroscopy,

agreement is found with recent experimental data. The main advantages of this

Raman spectroscopy over existing techniques are pointed out.

\\ ( http://arxiv.org/abs/0905.0824 , 752kb)

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arXiv:0905.0886

Date: Wed, 6 May 2009 18:39:06 GMT (2960kb,D)

Title: Quantum algorithm for Bose-Einstein condensate quantum fluid dynamics

Authors: Jeffrey Yepez and George Vahala and Linda Vahala

Categories: cond-mat.quant-gas quant-ph

Comments: 10 pages, 6 figures

Journal-ref: SPIE Quantum Information and Computation VII, Vol. 7342-21, 73420M

(2009)

DOI: 10.1117/12.819005

\\

The dynamics of vortex solitons in a BEC superfluid is studied. A quantum

lattice-gas algorithm (localization-based quantum computation) is employed to

examine the dynamical behavior of vortex soliton solutions of the

Gross-Pitaevskii equation (phi4 interaction nonlinear Schroedinger equation).

Quantum turbulence is studied in large grid numerical simulations: Kolmogorov

spectrum associated with a Richardson energy cascade occurs on large flow

scales. At intermediate scales a k^{-6} power law emerges, in a

classical-quantum transition from vortex filament reconnections to Kelvin

wave-acoustic wave coupling. The spontaneous exchange of intermediate vortex

rings is observed. Finally, at very small spatial scales a k^{-3} power law

emerges, characterizing fluid dynamics occurring within the scale size of the

vortex cores themselves, a characteristic Kelvin wave cascade region. Poincare

recurrence is studied: in the free non-interacting system, a fast Poincare

recurrence occurs for regular arrays of line vortices. The recurrence period is

used to demarcate dynamics driving the nonlinear quantum fluid towards

turbulence, since fast recurrence is an approximate symmetry of the nonlinear

quantum fluid at early times. This class of quantum algorithms is useful for

studying BEC superfluid dynamics over a broad range of wave numbers, from

quantum flow to a pseudo-classical inviscid flow regime to a Kolmogorov

inertial subrange.

\\ ( http://arxiv.org/abs/0905.0886 , 2960kb)

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arXiv:0905.0772

Date: Wed, 6 May 2009 08:20:03 GMT (895kb)

Title: Ultracold three-body collisions near overlapping Feshbach resonances

Authors: J. P. D'Incao and B. D. Esry

Categories: physics.atom-ph

Comments: 4 pages, 3 figures, 1 table

\\

We present a comprehensive collection of ultracold three-body collisions

properties near overlapping Feshbach resonances. Our results incorporate

variations of all scattering lengths and demonstrate novel collisional

behavior, such as atom-molecule interference effects. Taking advantage of the

unique ways in which these collisions reflect Efimov physics, new pathways to

control atomic and molecular losses open up. Further, we show that overlapping

resonances can greatly improve the chances of observing multiple Efimov

features in an ultracold quantum gas for nearly any system.

\\ ( http://arxiv.org/abs/0905.0772 , 895kb)

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arXiv:0905.0777

Date: Wed, 6 May 2009 12:53:31 GMT (2360kb)

Title: Integrated magneto-optical traps on a chip

Authors: S. Pollock, J. P. Cotter, A. Laliotis and E. A. Hinds

Categories: physics.atom-ph

Comments: 3 pages, 3 figures

\\

We have integrated magneto-optical traps (MOTs) into an atom chip by etching

pyramids into a silicon wafer. These have been used to trap atoms on the chip,

directly from a room temperature vapor of rubidium. This new atom trapping

method provides a simple way to integrate several atom sources on the same

chip. It represents a substantial advance in atom chip technology and offers

new possibilities for atom chip applications such as integrated single atom or

photon sources and molecules on a chip.

\\ ( http://arxiv.org/abs/0905.0777 , 2360kb)

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arXiv:0905.0902

Date: Wed, 6 May 2009 20:00:43 GMT (167kb)

Title: Exact quantum dynamics of a bosonic Josephson junction

Authors: Kaspar Sakmann, Alexej I. Streltsov, Ofir E. Alon, and Lorenz S.

Cederbaum

Categories: cond-mat.quant-gas cond-mat.other

Comments: 11 pages, 3 figures

\\

The quantum dynamics of a one-dimensional bosonic Josephson junction is

studied by solving the time-dependent many-boson Schr\"odinger equation

numerically exactly. Already for weak interparticle interactions and on short

time scales, the commonly-employed mean-field and many-body methods are found

to deviate substantially from the exact dynamics. The system exhibits rich

many-body dynamics like enhanced tunneling and a novel equilibration phenomenon

of the junction depending on the interaction, attributed to a quick loss of

coherence.

\\ ( http://arxiv.org/abs/0905.0902 , 167kb)

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arXiv:0905.0912

Date: Wed, 6 May 2009 20:40:14 GMT (214kb)

Title: Non-equilibrium Enhancement of Cooper Pairing in Cold Fermion Systems

Authors: Andrew Robertson and Victor Galitski

Categories: cond-mat.quant-gas cond-mat.supr-con

Comments: 4 pages, 3 figures

\\

Non-equilibrium stimulation of superfluidity in trapped Fermi gases is

discussed by analogy to the work of Eliashberg [G. M. Eliashberg, in

"Nonequilibrium Superconductivity," edited by D. N. Langenberg and A. I. Larkin

(North-Holland, New York, 1986)] on the microwave enhancement of

superconductivity. Optical excitation of the fermions balanced by heat loss due

to thermal contact with a boson bath and/or evaporative cooling enables

stationary non-equilibrium states to exist. Such a state manifests as a shift

of the quasiparticle spectrum to higher energies and this effect effectively

raises the pairing transition temperature. As an illustration, we calculate the

effective enhancement of Cooper pairing and superfluidity in both the normal

and superfluid phases for a mixture of Rb and Li in the limit of small

departure from equilibrium. It is argued that in experiment the desirable

effect is not limited to such small perturbations and the effective enhancement

of the pairing temperature may be quite large.

\\ ( http://arxiv.org/abs/0905.0912 , 214kb)

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arXiv:0905.0995

Date: Thu, 7 May 2009 10:53:52 GMT (261kb)

Title: Soliton dynamics at an interface between uniform medium and nonlinear

optical lattice

Authors: Fatkhulla Kh. Abdullaev, Ravil M. Galimzyanov, Marijana Brtka and

Lauro Tomio

Categories: cond-mat.quant-gas cond-mat.other

\\

We study trapping and propagation of a matter-wave soliton through the

interface between uniform medium and a nonlinear optical lattice (NOL).

Different regimes for transmission of a broad and a narrow soliton are

investigated. Reflections and transmissions of solitons are predicted as

function of the lattice phase. The existence of a threshold in the amplitude of

the nonlinear optical lattice, separating the transmission and reflection

regimes, is verified. The localized nonlinear surface state, corresponding to

the soliton trapped by the interface, is found. Variational approach

predictions are confirmed by numerical simulations for the original

Gross-Pitaevskii equation with nonlinear periodic potentials.

\\ ( http://arxiv.org/abs/0905.0995 , 261kb)

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arXiv:0905.1004

Date: Thu, 7 May 2009 11:32:35 GMT (515kb)

Title: Decoherence and entanglement in a bosonic Josephson junction:

Bose-enhanced quantum-Zeno control of phase-diffusion

Authors: Y. Khodorkovsky, G. Kurizki, and A. Vardi

Categories: cond-mat.quant-gas

Comments: 13 pages, 12 figures

\\

We study the effect of decoherence on dynamical phase diffusion in the

two-site Bose-Hubbard model. Starting with an odd parity excited coherent

state, the initial loss of single particle coherence varies from small bound

oscillations in the Rabi regime, through hyperbolic depletion in the Josephson

regime, to a Gaussian decay in the Fock regime. The inclusion of local-site

noise, measuring the relative number difference between the modes, is shown to

enhance phase-diffusion. In comparison, site-indiscriminate noise measuring the

population imbalance between the two quasi-momentum modes, slows down the loss

of single-particle coherence. Decoherence thus either enhances or suppresses

phase-diffusion, depending on the details of system-bath coupling and the

overlap of decoherence pointer states with collisional-entanglement pointer

states. The deceleration of phase-diffusion due to the coupling with the

environment may be viewed as a many-body quantum-Zeno effect. The extended

effective decay times in the presence of projective measurement, are further

enhanced with increasing number of particles $N$, by a bosonic factor of

$\sqrt{N}$ in the Fock regime and $N/\log{N}$ in the Josephson regime.

\\ ( http://arxiv.org/abs/0905.1004 , 515kb)

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arXiv:0905.1023

Date: Thu, 7 May 2009 13:09:27 GMT (71kb)

Title: The induced interaction in a Fermi gas with a BEC-BCS crossover

Authors: Zeng-Qiang Yu, Kun Huang, Lan Yin

Categories: cond-mat.quant-gas cond-mat.supr-con

Comments: 11 pages, 3 figures, to be published in PRA

\\

We study the effect of the induced interaction on the superfluid transition

temperature of a Fermi gas with a BEC-BCS crossover. The

Gorkov-Melik-Barkhudarov theory about the induced interaction is extended from

the BCS side to the entire crossover, and the pairing fluctuation is treated in

the approach by Nozi\`{e}res and Schmitt-Rink. At unitarity, the induced

interaction reduces the transition temperature by about twenty percent. In the

BCS limit, the transition temperature is reduced by a factor about 2.22, as

found by Gorkov and Melik-Barkhudarov. Our result shows that the effect of the

induced interaction is important both on the BCS side and in the unitary

region.

\\ ( http://arxiv.org/abs/0905.1023 , 71kb)

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arXiv:0905.1063

Date: Thu, 7 May 2009 17:52:32 GMT (317kb)

Title: A high-flux 2D MOT source for cold lithium atoms

Authors: T.G. Tiecke, S.D. Gensemer, A. Ludewig, and J.T.M. Walraven

Categories: cond-mat.quant-gas

Comments: 13 pages,9 figures, submitted to Phys.Rev.A

\\

We demonstrate a novel 2D MOT beam source for cold 6Li atoms. The source is

side-loaded from an oven operated at temperatures in the range 600<T<700 K. The

performance is analyzed by loading the atoms into a 3D MOT located 220 mm

downstream from the source. The maximum recapture rate of ~109 /s is obtained

for T=700 K and results in a total of up to 1010 trapped atoms. The recaptured

fraction is estimated to be 30(10)% and limited by beam divergence. The

most-probable velocity in the beam (alpha_z) is varied from 18 to 70 m/s by

increasing the intensity of a push beam. The source is quite monochromatic with

a full-width at half maximum velocity spread of 11 m/s at alpha_z=36 m/s,

demonstrating that side-loading completely eliminates beam contamination by hot

vapor from the oven. We identify depletion of the low-velocity tail of the oven

flux as the limiting loss mechanism. Our approach is suitable for other atomic

species.

\\ ( http://arxiv.org/abs/0905.1063 , 317kb)

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arXiv:0905.0931

Date: Thu, 7 May 2009 16:29:48 GMT (1446kb)

Title: Amplified Quantum Dynamics and Enhanced Parameter Sensitivity via

Coherent Feedback in Collective Atomic Spin Systems

Authors: Bradley A. Chase and JM Geremia

Categories: quant-ph

Comments: 28 Pages with 6 Figures. Please visit http://qmc.phys.unm.edu to

download C++ class files, mex/Matlab source code, and data files used to

generate all simulation data and figures in this paper as well as precompiled

mex libraries for the Windows x64 and intel Mac platforms

\\

We consider the effective dynamics obtained by double-passing a far-detuned

laser probe through a large atomic spin system. The net result of the

atom-field interaction is a type of coherent positive feedback that amplifies

the values of selected spin observables. An effective equation of motion for

the atomic system is presented, and an approximate 2-parameter model of the

dynamics is developed that should provide a viable approach to modeling even

the extremely large spin systems, with N>>1 atoms, encountered under typical

laboratory conditions.

Combining the nonlinear dynamics that result from the positive feedback with

continuous observation of the atomic spin offers an improvement in quantum

parameter estimation. We explore the possibility of reaching the Heisenberg

uncertainty scaling in atomic magnetometry without the need for any appreciable

spin-squeezing by analyzing our system via the quantum Cramer-Rao inequality.

Finally, we develop a realistic quantum parameter estimator for atomic

magnetometry that is based on a two-parameter family of Gaussian states and

investigate the performance of this estimator through numerical simulations. In

doing so, we identify several issues, such as numerical convergence and the

reduction of estimator bias, that must be addressed when incorporating our

parameter estimation methods into an actual laboratory setting.

\\ ( http://arxiv.org/abs/0905.0931 , 1446kb)

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\\

arXiv:0905.0970

Date: Thu, 7 May 2009 08:56:20 GMT (1279kb)

Title: Multi-Stability of Electromagnetically Induced Transparency in

Atom-Assisted Optomechanical Cavities

Authors: Yue Chang, T. Shi, Yu-xi Liu, C. P. Sun, and Franco Nori

Categories: quant-ph

Comments: 10 pages, 9 figures

\\

We study how an oscillating mirror affects the electromagnetically induced

transparency (EIT) of an atomic ensemble, which is confined in a gas cell

placed inside a micro-cavity with an oscillating mirror in one end. The

oscillating mirror is modeled as a quantum mechanical harmonic oscillator. The

cavity field acts as a probe light of the EIT system and also produces a light

pressure on the oscillating mirror. The back-action from the mirror to the

cavity field results in several (from one to five) steady-states for this

atom-assisted optomechanical cavity, producing a complex structure in its EIT.

We calculate the susceptibility with respect to the few (from one to three)

stable solutions found here for the equilibrium positions of the oscillating

mirror. We find that the EIT of the atomic ensemble can be significantly

changed by the oscillating mirror, and also that the various steady states of

the mirror have different effects on the EIT.

\\ ( http://arxiv.org/abs/0905.0970 , 1279kb)

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\\

arXiv:0905.0958

Date: Thu, 7 May 2009 07:32:19 GMT (1118kb)

Title: Line shapes of optical Feshbach resonances near the intercombination

transition of bosonic Ytterbium

Authors: M. Borkowski, R. Ciurylo, P. S. Julienne, S. Tojo, K. Enomoto, Y.

Takahashi

Categories: physics.atom-ph

\\

The properties of bosonic Ytterbium photoassociation spectra near the

intercombination transition $^{1}S_{0}$--$^{3}P_{1}$ are studied theoretically

at ultra low temperatures. We demonstrate how the shapes and intensities of

rotational components of optical Feshbach resonances are affected by mass

tuning of the scattering properties of the two colliding ground state atoms.

Particular attention is given to the relationship between the magnitude of the

scattering length and the occurrence of shape resonances in higher partial

waves of the van der Waals system. We develop a mass scaled model of the

excited state potential that represents the experimental data for different

isotopes. The shape of the rotational photoassociation spectrum for various

bosonic Yb isotopes can be qualitatively different.

\\ ( http://arxiv.org/abs/0905.0958 , 1118kb)

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The replacements:

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\\

arXiv:0811.2798

replaced with revised version Sat, 2 May 2009 08:13:46 GMT (641kb)

Title: Probing condensate order in deep optical lattices

Authors: Kuei Sun, Courtney Lannert, Smitha Vishveshwara

Categories: cond-mat.other

Comments: 15 pages, 9 figures, RevTeX; content changed, references changed

Journal-ref: Phys. Rev. A 79, 043422 (2009)

DOI: 10.1103/PhysRevA.79.043422

\\ ( http://arxiv.org/abs/0811.2798 , 641kb)

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\\

arXiv:0812.0266

replaced with revised version Mon, 4 May 2009 18:50:40 GMT (495kb)

Title: Threshold of a Random Laser with Cold Atoms

Authors: Luis S. Froufe-P\'erez, William Guerin (INLN), R\'emi Carminati

(LPEM), Robin Kaiser (INLN)

Categories: physics.atom-ph cond-mat.dis-nn physics.optics

Journal-ref: Physical Review Letters 102 (2009) 173903

\\ ( http://arxiv.org/abs/0812.0266 , 495kb)

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\\

arXiv:0812.1581

replaced with revised version Fri, 1 May 2009 20:11:11 GMT (1998kb)

Title: Superconductivity close to the Mott state: From condensed-matter systems

to superfluidity in optical lattices

Authors: Karyn Le Hur and T. Maurice Rice

Categories: cond-mat.supr-con cond-mat.str-el

Comments: 98 pages and 18 figures; Final version (references added and

misprints corrected)

\\ ( http://arxiv.org/abs/0812.1581 , 1998kb)

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\\

arXiv:0902.2427

replaced with revised version Mon, 4 May 2009 18:44:32 GMT (125kb)

Title: Bistable Mott-insulator to superfluid phase transition in cavity

optomechanics

Authors: W. Chen, K. Zhang, D. S. Goldbaum, M. Bhattacharya, P. Meystre

Categories: quant-ph cond-mat.other

Comments: 5 pages, 3 figures

\\ ( http://arxiv.org/abs/0902.2427 , 125kb)

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\\

arXiv:0904.3131

replaced with revised version Mon, 4 May 2009 13:46:36 GMT (206kb)

Title: Fortran programs for the time-dependent Gross-Pitaevskii equation in a

fully anisotropic trap

Authors: P. Muruganandam and S. K. Adhikari

Categories: cond-mat.quant-gas nlin.PS physics.comp-ph

Comments: 34 pages, 11 figures, 18 Fortran programs included, output files (not

included) available in Comput. Phys. Commun. Library after publication

\\ ( http://arxiv.org/abs/0904.3131 , 206kb)

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\\

arXiv:0904.4474

replaced with revised version Mon, 4 May 2009 15:08:36 GMT (49kb)

Title: Collective modes and superflow instabilities of strongly correlated

Fermi superfluids

Authors: R. Ganesh, A. Paramekanti, A. A. Burkov

Categories: cond-mat.supr-con cond-mat.quant-gas

Comments: 14 pages, 10 figures. Corrected 3d phase diagram

\\ ( http://arxiv.org/abs/0904.4474 , 49kb)

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\\

arXiv:0904.4862

replaced with revised version Mon, 4 May 2009 11:13:35 GMT (10kb)

Title: A quantum de Finetti theorem in phase space representation

Authors: Anthony Leverrier, Nicolas J. Cerf

Categories: quant-ph

Comments: 5 pages

\\ ( http://arxiv.org/abs/0904.4862 , 10kb)

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\\

arXiv:0811.2219

replaced with revised version Tue, 5 May 2009 20:26:38 GMT (192kb)

Title: State diagrams for harmonically trapped bosons in optical lattices

Authors: Marcos Rigol, George G. Batrouni, Valery G. Rousseau, Richard T.

Scalettar

Categories: cond-mat.other cond-mat.stat-mech

Comments: 10 pages, 11 figures, published version

Journal-ref: Phys. Rev. A 79, 053605 (2009)

DOI: 10.1103/PhysRevA.79.053605

\\ ( http://arxiv.org/abs/0811.2219 , 192kb)

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\\

arXiv:0807.3358

replaced with revised version Thu, 7 May 2009 12:32:27 GMT (2323kb,D)

Title: Quantum interface between light and atomic ensembles

Authors: K. Hammerer, A.S. Sorensen, E.S. Polzik

Categories: quant-ph cond-mat.other

Comments: 56 pages, 22 figures, 3.3MB; to be published in Reviews of Modern

Physics; completely revised, final version

\\ ( http://arxiv.org/abs/0807.3358 , 2323kb)

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\\

arXiv:0904.3376

replaced with revised version Thu, 7 May 2009 07:17:05 GMT (246kb)

Title: Stability and chaotic behavior of Bose-Einstein condensates in optical

lattices with two- and three-body interactions

Authors: Yan Chen, Ke-Zhi Zhang, and Yong Chen

Categories: cond-mat.quant-gas

Comments: 11 pages, 6 figures

\\ ( http://arxiv.org/abs/0904.3376 , 246kb)

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\\

arXiv:0904.2515

replaced with revised version Thu, 7 May 2009 11:47:06 GMT (130kb)

Title: Collisional losses, decoherence, and frequency shifts in optical lattice

clocks with bosons

Authors: Ch. Lisdat, J.S.R. Vellore Winfred, T. Middelmann, F. Riehle, U. Sterr

Categories: physics.atom-ph

Comments: 4 pages, 3 figures

\\ ( http://arxiv.org/abs/0904.2515 , 130kb)

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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 Tue Jun 16 2009 - 10:27:50 EST

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