Dear subscribers,
This week's selection was compiled by Chris Foster, and contains 33 new
abstracts and 10 replacements.
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arXiv:1006.3673
Date: Fri, 18 Jun 2010 12:19:04 GMT (235kb)
Title: Superfluid/ferromagnet/superfluid junction and $\pi$-phase in a
superfluid Fermi gas
Authors: Takashi Kashimura, Shunji Tsuchiya, and Yoji Ohashi
Categories: cond-mat.quant-gas
Comments: 22 pages, 14 figures
\\
We investigate the possibility of superfluid/ferromagnet/superfluid
(SFS)-junction in a superfluid Fermi gas. To examine this possibility in a
simple manner, we consider an attractive Hubbard model at $T=0$ within the
mean-field theory. When a potential barrier is embedded in a superfluid Fermi
gas with population imbalance ($N_\uparrow>N_\downarrow$, where $N_\sigma$ is
the number of atoms with pseudospin $\sigma=\uparrow,\downarrow$), this barrier
is shown to be {\it magnetized} in the sense that excess $\uparrow$-spin atoms
are localized around it. The resulting superfluid Fermi gas is spatially
divided into two by this {\it ferromagnet}, so that one obtains a junction
similar to the superconductor/ferromagnet/superconductor-junction discussed in
superconductivity. Indeed, we show that the so-called $\pi$-phase, which is a
typical phenomenon in the SFS-junction, is realized, where the superfluid order
parameter changes its sign across the junction. Our results would be useful for
the study of magnetic effects on fermion superfluidity using an ultracold Fermi
gas.
\\ ( http://arxiv.org/abs/1006.3673 , 235kb)
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arXiv:1006.3687 (*cross-listing*)
Date: Fri, 18 Jun 2010 13:05:54 GMT (1319kb)
Title: Two - dimensional solitons in media with the stripe - shaped
nonlinearity modulation
Authors: Nguyen Viet Hung, Pawe\lZi\'n, Marek Trippenbach and Boris A. Malomed
Categories: nlin.PS cond-mat.quant-gas
Comments: 9 pages, 15 figures
\\
We introduce a model of media with the cubic attractive nonlinearity
concentrated along a single or double stripe in the two-dimensional (2D) plane.
The model can be realized in terms of nonlinear optics (in the spatial and
temporal domains alike) and BEC. In recent works, it was concluded that search
for stable 2D solitons in models with a spatially localized self-attractive
nonlinearity is a challenging problem. We make use of the variational
approximation (VA) and numerical methods to investigate conditions for the
existence and stability of solitons in the present setting. The result
crucially depends on the transverse shape of the stripe: while the rectangular
profile supports stable 2D solitons, its smooth Gaussian-shaped counterpart
makes all the solitons unstable. The double stripe with the rectangular profile
admit stable solitons of three distinct types: symmetric and asymmetric ones
with a single peak, and double-peak symmetric solitons. The shape and stability
of single-peak solitons of either type are accurately predicted by the VA.
Collisions between stable solitons are briefly considered too, by means of
direct simulations. Depending on the relative velocity we observe excitation,
decay or catastrophic self focusing.
\\ ( http://arxiv.org/abs/1006.3687 , 1319kb)
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arXiv:1006.3695
Date: Fri, 18 Jun 2010 14:06:18 GMT (128kb)
Title: Exact exact solutions of the Gross-Pitaevskii equation for stable vortex
modes
Authors: Lei Wu, Lu Li, Jie-Fang Zhang, Dumitru Mihalache, Boris A. Malomed,
and W. M. Liu
Categories: cond-mat.quant-gas math-ph math.MP physics.optics
Comments: 5 pages, 6 figures, to appear in Phys. Rev. A
\\
We construct exact solutions of the Gross-Pitaevskii equation for solitary
vortices, and approximate ones for fundamental solitons, in 2D models of
Bose-Einstein condensates with a spatially modulated nonlinearity of either
sign and a harmonic trapping potential. The number of vortex-soliton (VS) modes
is determined by the discrete energy spectrum of a related linear
Schr\"{o}dinger equation. The VS families in the system with the attractive and
repulsive nonlinearity are mutually complementary. \emph{% Stable} VSs with
vorticity $S\geq 2$ and those corresponding to higher-order radial states are
reported for the first time, in the case of the attraction and repulsion,
respectively.
\\ ( http://arxiv.org/abs/1006.3695 , 128kb)
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arXiv:1006.3705 (*cross-listing*)
Date: Fri, 18 Jun 2010 14:32:09 GMT (15kb)
Title: Solitary waves of Bose-Einstein condensed atoms confined in finite rings
Authors: J. Smyrnakis, M. Magiropoulos, G. M. Kavoulakis, A. D. Jackson
Categories: cond-mat.quant-gas quant-ph
Comments: 6 pages, 2 figures
\\
Motivated by recent progress in trapping Bose-Einstein condensed atoms in
toroidal potentials, we examine solitary-wave solutions of the nonlinear
Schr\"odinger equation subject to periodic boundary conditions. When the
circumference of the ring is much larger than the size of the wave, the density
profile is well approximated by that of an infinite ring, however the density
and the velocity of propagation cannot vanish simultaneously. When the size of
the ring becomes comparable to the size of the wave, the density variation
becomes sinusoidal and the velocity of propagation saturates to a constant
value.
\\ ( http://arxiv.org/abs/1006.3705 , 15kb)
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arXiv:1006.3767
Date: Fri, 18 Jun 2010 18:12:44 GMT (360kb)
Title: Atomic population distribution in the output ports of cold-atom
interferometers with optical splitting and recombination
Authors: Ebubechukwu O. Ilo-Okeke and Alex A. Zozulya
Categories: physics.atom-ph
Comments: 25 pages, 7 figures
\\
Cold-atom interferometers with optical splitting and recombination use
off-resonant laser beams to split a cloud of Bose-Einstein condensate (BEC)
into two clouds that travel along different paths and are then recombined again
using optical beams. After the recombination, the BEC in general populates both
the cloud at rest and the moving clouds. Measuring relative number of atoms in
each of these clouds yields information about the relative phase shift
accumulated by the atoms in the two moving clouds during the interferometric
cycle. We derive the expression for the probability of finding any given number
of atoms in each of the clouds, discuss features of the probability density
distribution, analyze its dependence on the relative accumulated phase shift as
a function of the strength of the interatomic interactions, and compare our
results with experiment.
\\ ( http://arxiv.org/abs/1006.3767 , 360kb)
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arXiv:1006.3799 (*cross-listing*)
Date: Fri, 18 Jun 2010 20:17:29 GMT (3627kb,D)
Title: Single-Atom Resolved Fluorescence Imaging of an Atomic Mott Insulator
Authors: Jacob F. Sherson, Christof Weitenberg, Manuel Endres, Marc Cheneau,
Immanuel Bloch, Stefan Kuhr
Categories: cond-mat.quant-gas quant-ph
\\
The reliable detection of single quantum particles has revolutionized the
field of quantum optics and quantum information processing. For several years,
researchers have aspired to extend such detection possibilities to larger scale
strongly correlated quantum systems, in order to record a snapshot of a quantum
fluid in which each underlying quantum particle is detected. Here we report on
fluorescence imaging of strongly interacting bosonic Mott insulators in an
optical lattice with single-atom and single-site resolution. From our images,
we fully reconstruct the atom distribution on the lattice and identify
individual excitations with high fidelity. A comparison of the radially
averaged density and variance distribution with theory provides a precise
in-situ temperature measurement from single images. We observe Mott-insulating
plateaus with near zero entropy and clearly resolve the high entropy rings
separating them although their width is of the order of only a single lattice
site. Our experiments open a new avenue for the manipulation and analysis of
strongly interacting quantum gases on a lattice, as well as for quantum
information processing with ultracold atoms. Using the high spatial resolution,
it is now possible to directly address regions of high entropy, a crucial
requirement e.g. for the implementation of novel cooling schemes for atoms on a
lattice. Furthermore, hidden order parameters of topological quantum phases
that manifest themselves as expectation values of a string of operators acting
on different sites can be detected.
\\ ( http://arxiv.org/abs/1006.3799 , 3627kb)
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arXiv:1006.3839 (*cross-listing*)
Date: Sat, 19 Jun 2010 04:33:29 GMT (188kb)
Title: Matter-wave solitons and finite-amplitude Bloch waves in optical
lattices with a spatially modulated nonlinearity
Authors: Jie-Fang Zhang, Yi-Shen Li, Jianping Meng, Lei Wu, and Boris A.
Malomed
Categories: cond-mat.quant-gas math-ph math.MP physics.optics
Comments: 9 pages, 10 figures
\\
We investigate solitons and nonlinear Bloch waves in Bose-Einstein
condensates trapped in optical lattices. By introducing specially designed
localized profiles of the spatial modulation of the attractive nonlinearity, we
construct an infinite number of exact soliton solutions in terms of the Mathieu
and elliptic functions, with the chemical potential belonging to the
semi-infinite bandgap of the optical-lattice-induced spectrum. Starting from
the exact solutions, we employ the relaxation method to construct generic
families of soliton solutions in a numerical form. The stability of the
solitons is investigated through the computation of the eigenvalues for small
perturbations, and also by direct simulations. Finally, we demonstrate a
virtually exact (in the numerical sense) composition relation between nonlinear
Bloch waves and solitons.
\\ ( http://arxiv.org/abs/1006.3839 , 188kb)
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arXiv:1006.3893
Date: Sat, 19 Jun 2010 21:22:55 GMT (256kb)
Title: The Nonlinear Dirac Equation in Bose-Einstein Condensates: Relativistic
Linear Stability Equations, Nonlinear Localized Modes, and Cherenkov
Radiation
Authors: L. H. Haddad and L. D. Carr
Categories: cond-mat.quant-gas math-ph math.MP
Comments: 5 pages, 2 figures
\\
Bose-Einstein condensates in a honeycomb optical lattice are described by a
nonlinear Dirac equation (NLDE) in the long wavelength, mean field limit, a
relativistic generalization of the nonlinear Schr\"odinger equation. We present
a variety of localized solutions of the NLDE: skyrmions, solitons, vortices,
and half-quantum vortices. We then derive and solve the associated relativistic
linear stability equations (RLSE). We study stability via the RLSE of localized
and uniform background solutions and present an experimentally observable
effect of our calculations in the form of Cherenkov radiation.
\\ ( http://arxiv.org/abs/1006.3893 , 256kb)
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arXiv:1006.3911
Date: Sun, 20 Jun 2010 06:16:49 GMT (797kb,D)
Title: Numerical generation of a vortex ring cascade in quantum turbulence
Authors: Robert M. Kerr
Categories: cond-mat.quant-gas nlin.PS
Comments: 22 pages 17 figures
\\
A symmetric anti-parallel quantum pair of vortices is simulated using the
three-dimensional Gross-Pitaevski equations. The initial development before
cores interact directly demonstrates the traditional vortex dynamics of
stretching, curvature and torsion in a manner consistent with a filament
calculation and simulations of the classical, ideal Euler equations. Once the
cores begin to interact, reconnection develops in the vacuum that forms between
the pair. Out of the reconnection region, vortex waves are emitted with
properties similar to waves in the local induction approximation. These waves
propagate down the initial vortex and deepen. When they deepen far enough,
secondary reconnections occur and vortex rings form. Near this time, spectra
have a $k^{-3}$ regime. As the vortex rings fully separate, the high wavenumber
spectra grow until, at the final time simulated, spectra in two directions
develop nearly -5/3 subranges. This occurs without the dissipation of energy.
Preliminary analysis of the flow of energies in spectral scale and physical
space is discussed.
\\ ( http://arxiv.org/abs/1006.3911 , 797kb)
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arXiv:1006.4014
Date: Mon, 21 Jun 2010 08:57:04 GMT (24kb)
Title: New Developments in Quantum Algorithms
Authors: Andris Ambainis
Categories: quant-ph cs.CC cs.DS
Comments: 11 pages, 1 figure, to appear as an invited survey talk at MFCS'2010
\\
In this survey, we describe two recent developments in quantum algorithms.
The first new development is a quantum algorithm for evaluating a Boolean
formula consisting of AND and OR gates of size N in time O(\sqrt{N}). This
provides quantum speedups for any problem that can be expressed via Boolean
formulas. This result can be also extended to span problems, a generalization
of Boolean formulas. This provides an optimal quantum algorithm for any Boolean
function in the black-box query model.
The second new development is a quantum algorithm for solving systems of
linear equations. In contrast with traditional algorithms that run in time
O(N^{2.37...}) where N is the size of the system, the quantum algorithm runs in
time O(\log^c N). It outputs a quantum state describing the solution of the
system.
\\ ( http://arxiv.org/abs/1006.4014 , 24kb)
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arXiv:1006.4036
Date: Mon, 21 Jun 2010 11:24:30 GMT (351kb,D)
Title: Quantum entanglement of nanocantilevers
Authors: C. Joshi, A. Hutter, F. Zimmer, M. Jonson, E. Andersson, P. Ohberg
Categories: quant-ph
Comments: 9 pages, 8 figures
\\
We propose a scheme to entangle two mechanical nanocantilevers through
indirect interactions mediated by a gas of ultra cold atoms. We envisage a
system of nanocantilevers magnetically coupled to a Bose-Einstein condensate of
atoms and focus on studying the dark states of the system. These dark states
are entangled states of the two nanocantilevers, with no coupling to the atomic
condensate. In the absence of dissipation, the degree of entanglement is found
to oscillate with time, while if dissipation is included the system is found to
relax to a time-independent statistical mixture of dark states. This opens up
the possibility of achieving long-lived entangled nanocantilever states.
\\ ( http://arxiv.org/abs/1006.4036 , 351kb)
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arXiv:1006.4049
Date: Mon, 21 Jun 2010 12:20:59 GMT (644kb)
Title: Localized and extended states in a disordered trap
Authors: Luca Pezz\'e (LCFIO), Laurent Sanchez-Palencia (LCFIO)
Categories: cond-mat.other
Comments:
\\
We study Anderson localization in a disordered potential combined with a
harmonic trap. We show that the spectrum displays both localized and extended
states, which coexist at intermediate energies. In the region of coexistence,
we find that the extended states result from confinement by the trap and are
weakly affected by the disorder. Conversely, the localized states correspond to
eigenstates of the disordered potential, which are only affected by the trap
via an inhomogeneous energy shift. These results are directly relevant to
disordered quantum gases and we propose a realistic scheme to observe the
coexistence of localized and extended states in these systems.
\\ ( http://arxiv.org/abs/1006.4049 , 644kb)
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arXiv:1006.4052
Date: Mon, 21 Jun 2010 12:24:41 GMT (1022kb)
Title: The equation of state of ultracold Bose and Fermi gases: a few examples
Authors: Sylvain Nascimb\`ene (LKB - Lhomond), Nir Navon (LKB - Lhomond),
Fr\'ed\'eric Chevy (LKB - Lhomond), C. Salomon (LKB - Lhomond)
Categories: cond-mat.quant-gas
Comments: 14 pages, 6 figures
\\
We describe a powerful method for determining the equation of state of an
ultracold gas from in situ images. The method provides a measurement of the
local pressure of an harmonically trapped gas and we give several applications
to Bose and Fermi gases. We obtain the grand-canonical equation of state of a
spin-balanced Fermi gas with resonant interactions as a function of
temperature. We compare our equation of state with an equation of state
measured by the Tokyo group, that reveals a significant difference in the
high-temperature regime. The normal phase, at low temperature, is well
described by a Landau Fermi liquid model, and we observe a clear thermodynamic
signature of the superfluid transition. In a second part we apply the same
procedure to Bose gases. From a single image of a quasi ideal Bose gas we
determine the equation of state from the classical to the condensed regime.
Finally the method is applied to a Bose gas in a 3D optical lattice in the Mott
insulator regime. Our equation of state directly reveals the Mott insulator
behavior and is suited to investigate finite-temperature effects.
\\ ( http://arxiv.org/abs/1006.4052 , 1022kb)
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arXiv:1006.4067
Date: Mon, 21 Jun 2010 13:58:39 GMT (227kb)
Title: Driven optical lattices as strong-field simulators
Authors: Stephan Arlinghaus and Martin Holthaus
Categories: cond-mat.other
Comments: 5 pages, 5 figures
Journal-ref: Phys. Rev. A 81, 063612 (2010)
DOI: 10.1103/PhysRevA.81.063612
\\
We argue that ultracold atoms in strongly shaken optical lattices can be
subjected to conditions similar to those experienced by electrons in
laser-irradiated crystalline solids, but without introducing secondary
polarization effects. As a consequence one can induce nonperturbative
multiphoton-like resonances due to the mutual penetration of ac-Stark-shifted
Bloch bands. These phenomena can be detected with a combination of currently
available laboratory techniques.
\\ ( http://arxiv.org/abs/1006.4067 , 227kb)
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arXiv:1006.4205 (*cross-listing*)
Date: Tue, 22 Jun 2010 03:57:15 GMT (74kb,D)
Title: Other incarnations of the Gross-Pitaevskii dark soliton
Authors: Indubala I Satija and Radha Balakrishnan
Categories: quant-ph cond-mat.quant-gas
\\
We show that the dark soliton of the Gross-Pitaevskii equation (GPE) that
describes the Bose-Einstein condensate (BEC) density of a system of weakly
repulsive bosons, also describes that of a system of strongly repulsive hard
core bosons at half filling. As a consequence of this, the GPE soliton gets
related to the magnetic soliton in an easy-plane ferromagnet, where it
describes the square of the in-plane magnetization of the system. These
relationships are shown to be useful in understanding various characteristics
of solitons in these distinct many-body systems.
\\ ( http://arxiv.org/abs/1006.4205 , 74kb)
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arXiv:1006.4277
Date: Tue, 22 Jun 2010 12:36:25 GMT (282kb)
Title: Spatially-antisymmetric localization of matter wave in a bichromatic
optical lattice
Authors: Y. Cheng and S. K. Adhikari
Categories: cond-mat.quant-gas
\\
By direct numerical simulation of the time-dependent Gross-Pitaevskii
equation using the split-step Fourier spectral method we study the
double-humped localization of a cigar-shaped Bose-Einstein condensate (BEC) in
a one-dimensional bichromatic quasi-periodic optical-lattice potential, as used
in a recent experiment on the localization of a BEC [Roati et al., Nature 453,
895 (2008)]. Such states are spatially antisymmetric and are excited modes of
Anderson localization. Where possible, we have compared the numerical results
with a variational analysis. We also demonstrate the stability of the localized
double-humped BEC states under small perturbation.
\\ ( http://arxiv.org/abs/1006.4277 , 282kb)
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arXiv:1006.4315
Date: Tue, 22 Jun 2010 15:30:38 GMT (4644kb,D)
Title: Anomalous vortex ring velocities induced by thermally-excited Kelvin
waves and counterflow effects in superfluids
Authors: Giorgio Krstulovic and Marc Brachet
Categories: cond-mat.stat-mech
\\
Dynamical counterflow effects on vortex evolution under the truncated
Gross-Pitaevskii equation are investigated. Standard longitudinal mutual
friction effects are produced and a dilatation of vortex rings is obtained at
large counterflow. A strong temperature-dependent anomalous slowdown of vortex
rings is observed and attributed to the presence of thermally exited Kelvin
waves. This generic effect of finite-temperature superfluids is estimated using
energy equipartition and orders of magnitude are given for weakly interacting
Bose-Einstein condensates and superfluid $^4{\rm He}$.
\\ ( http://arxiv.org/abs/1006.4315 , 4644kb)
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arXiv:1006.4426
Date: Wed, 23 Jun 2010 06:48:49 GMT (397kb)
Title: A nonlinear quantum piston for the controlled generation of vortex rings
Authors: Natalia G. Berloff, Victor M. Perez-Garcia
Categories: cond-mat.quant-gas nlin.PS
\\
We propose a simple way to manage interactions in Bose-Einstein condensates
to generate vortex rings in a highly controllable way.
The vortex rings are generated under the action of a quantum analogue of a
classical piston pushing the condensed atoms through a small aperture.
\\ ( http://arxiv.org/abs/1006.4426 , 397kb)
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arXiv:1006.4429
Date: Wed, 23 Jun 2010 06:54:22 GMT (741kb)
Title: Quantitative study of 3D and 2D strong localization of matter waves by
atomic scatterers
Authors: Mauro Antezza (LKB - Lhomond), Yvan Castin (LKB - Lhomond), David
Hutchinson
Categories: cond-mat.quant-gas
Comments:
\\
We study the strong localization of atomic matter waves in a disordered
potential created by atoms pinned at the nodes of a lattice, for both 3D and 2D
systems. The localization length of the matter wave, the density of localized
states, and the occurrence of energy mobility edges (for the 3D system), are
numerically investigated as a function of the effective scattering length
between the atomic matter wave and the pinned atoms. Both positive and negative
matter wave energies are explored. Interesting features of the density of
states are discovered at negative energies, where maximums in the density of
bound states for the system can be interpreted in terms of bound states of a
matter wave atom with a few pinned atomic scatterers. In 3D we found evidences
of up to three mobility edges, one at positive energies, and two at negative
energies, the latter corresponding to transitions between extended and
localized bound states. In 2D, no mobility edge is found, and a rapid
exponential-like increase of the localization length is observed at high
energy.
\\ ( http://arxiv.org/abs/1006.4429 , 741kb)
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arXiv:1006.4450
Date: Wed, 23 Jun 2010 09:19:15 GMT (56kb)
Title: Two-superfluid Model of Two-component Bose-Einstein Condensates; First
Sound and Second Sound
Authors: Shungo. Ishino, Hiromitsu Takeuchi, Makoto. Tsubota
Categories: cond-mat.quant-gas
Comments: 6 pages, 1 figures, submitted to Journal of Low Temperature Physics
\\
Superfluid $^4$He at a finite temperature is described by the two-fluid model
with the normal fluid component and the superfluid component.We formulate the
two-fluid model for two-component BECs, namely two-superfluid model, starting
from the coupled Gross-Pitaevskii equations.The two-superfluid model well
corresponds to the two-fluid model in superfluid $^4$He.In a special condition,
the two sound modes in the two-superfluid model behave like first and second
sounds in the two-fluid model of superfluid $^4$He.
\\ ( http://arxiv.org/abs/1006.4450 , 56kb)
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arXiv:1006.4488
Date: Wed, 23 Jun 2010 11:57:56 GMT (1334kb)
Title: Counterflow Quantum Turbulence and the Instability in Two-component
Bose-Einstein Condensates
Authors: Shungo Ishino, Hiromitsu Takeuchi, Makoto Tsubota
Categories: cond-mat.quant-gas
Comments: 7 pages, 5 figures, submitted to Journal of Low Temperature Physics
\\
We theoretically study the nonlinear dynamics of the instability of
counter-superflow in two miscible Bose-Einstein condensates. The condensates
become unstable when the relative velocity exceeds a critical value, which is
called counter-superflow instability. We reveal that the counter-superflow
instability can lead to quantum turbulence by numerically solving the coupled
Gross-Pitaevskii equations. The modes amplified by the instability grow into
solitons and decay into quantized vortices.Eventually, the vortices become
tangled and quantum turbulence of two superfluids. We show that this process
may occur in experiments by investigating the dynamics in a 2D trapped system.
\\ ( http://arxiv.org/abs/1006.4488 , 1334kb)
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arXiv:1006.4526
Date: Wed, 23 Jun 2010 14:14:54 GMT (308kb,D)
Title: Laser cooling with a single laser beam and a planar diffractor
Authors: Matthieu Vangeleyn, Paul F. Griffin, Erling Riis and Aidan S. Arnold
Categories: physics.atom-ph
Comments: 3 pages, 4 figures
\\
A planar triplet of diffraction gratings is used to transform a single laser
beam into a four-beam tetrahedral magneto-optical trap. This `flat' pyramid
diffractor geometry is ideal for future microfabrication. We demonstrate the
technique by trapping and subsequently sub-Doppler cooling 87Rb atoms to
30microKelvin.
\\ ( http://arxiv.org/abs/1006.4526 , 308kb)
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arXiv:1006.4532 (*cross-listing*)
Date: Wed, 23 Jun 2010 14:39:33 GMT (1386kb,D)
Title: Optimized magnetic lattices for ultracold atomic ensembles
Authors: Roman Schmied, Dietrich Leibfried, Robert J. C. Spreeuw, and Shannon
Whitlock
Categories: quant-ph cond-mat.quant-gas
Comments: 11 pages, 5 figures
\\
We introduce a general method for designing tailored lattices of magnetic
microtraps for ultracold atoms, on the basis of patterned permanently
magnetized films. A fast numerical algorithm is used to automatically generate
patterns which provide optimal atom confinement while respecting desired
lattice symmetries and trap parameters. The algorithm can produce finite and
infinite lattices of any plane symmetry; we focus specifically on square and
triangular lattices which are of interest to future experiments. Typical trap
parameters are discussed as well as the impact of realistic imperfections such
as finite lithographic resolution and magnetic inhomogeneity. The presented
designer lattices open new avenues for quantum simulation and quantum
information processing with ultracold atoms on atom chips.
\\ ( http://arxiv.org/abs/1006.4532 , 1386kb)
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arXiv:1006.4579
Date: Wed, 23 Jun 2010 16:07:28 GMT (61kb)
Title: Dynamics of a quantum quench in an ultra-cold atomic BCS superfluid
Authors: Chih-Chun Chien and Bogdan Damski
Categories: cond-mat.quant-gas cond-mat.supr-con
Comments: 4 pages, 3 figures
Report-no: LAUR 10-04106
\\
We study dynamics of an ultra-cold atomic BCS superfluid driven towards the
BCS superfluid-Fermi liquid quantum critical point by a gradual decrease of the
pairing interaction. We analyze how the BCS superfluid falls out of equilibrium
and show that the non-equilibrium gap and Cooper pair size reflect critical
properties of the transition. We observe three stages of evolution: adiabatic
where the Cooper pair size is inversely proportional to the equilibrium gap,
weakly non-equilibrium where it is inversely proportional to the
non-equilibrium gap, and strongly non-equilibrium where it decouples from both
equilibrium and non-equilibrium gap. These phenomena should stimulate future
experimental characterization of non-equilibrium ultra-cold atomic BCS
superfluids.
\\ ( http://arxiv.org/abs/1006.4579 , 61kb)
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arXiv:1006.4619
Date: Wed, 23 Jun 2010 19:18:58 GMT (30kb)
Title: Origin of nonlinear optical processes in matter-wave superradiance
Authors: L. Deng and E.W. Hagley
Categories: cond-mat.quant-gas quant-ph
\\
We study a highly efficient, matter-wave amplification mechanism in a
longitudinally-excited, Bose-Einstein condensate and reveal a very large
enhancement due to nonlinear gain from a sixmatter- optical, wave-mixing
process involving four photons. Under suitable conditions this
opticallydegenerate, four-photon process can be stronger than the usual
two-photon inelastic light scattering mechanism, leading to nonlinear growth of
the observed matter-wave scattering independent of any enhancement from bosonic
stimulation. Our theoretical framework can be extended to encompass even
higher-order, nonlinear superradiant processes that result in higher-order
momentum transfer.
\\ ( http://arxiv.org/abs/1006.4619 , 30kb)
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arXiv:1006.4666
Date: Thu, 24 Jun 2010 00:51:31 GMT (2872kb)
Title: Markovian Master Equations: A Critical Study
Authors: \'Angel Rivas, A. Douglas K. Plato, Susana F. Huelga and Martin B.
Plenio
Categories: quant-ph
Comments: 40 pages, 14 figures
\\
We derive Markovian master equations of single and interacting harmonic
systems in different scenarios, including strong internal coupling. By
comparing the dynamics resulting from the corresponding Markovian master
equations with exact numerical simulations of the evolution of the global
system, we precisely delimit their validity regimes and assess the robustness
of the assumptions usually made in the process of deriving the reduced
dynamics. The proposed method is sufficiently general to suggest that the
conclusions made here are widely applicable to a large class of settings
involving interacting chains subject to a weak interaction with an environment.
\\ ( http://arxiv.org/abs/1006.4666 , 2872kb)
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arXiv:1006.4674 (*cross-listing*)
Date: Thu, 24 Jun 2010 02:30:44 GMT (152kb,D)
Title: Spin gradient demagnetization cooling of ultracold atoms
Authors: Patrick Medley, David M. Weld, Hirokazu Miyake, David E. Pritchard,
and Wolfgang Ketterle
Categories: cond-mat.quant-gas physics.atom-ph
Comments: 12 pages, 4 figures
\\
Attainment of lower temperatures has frequently enabled discoveries of new
physical phenomena, from superconductivity to Bose-Einstein condensation. Here
we describe and demonstrate a cooling method, spin gradient demagnetization,
which has several novel features: It operates directly in the spin degree of
freedom, it can be applied to atoms in an optical lattice, and it is able to
reach positive and negative spin temperatures of $\pm$50 picokelvin, the lowest
temperatures which have been achieved in any system. The cooling method
consists of applying a time-varying magnetic field gradient to a spin mixture
of ultracold atoms. The spin system can also be used to cool other degrees of
freedom, and we have used this coupling to reduce the temperature of an
apparently equilibrated sample of rubidium atoms in an optical lattice to 350
picokelvin. These results open a realistic path to the observation of magnetic
quantum phase transitions in optical lattices.
\\ ( http://arxiv.org/abs/1006.4674 , 152kb)
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arXiv:1006.4705
Date: Thu, 24 Jun 2010 07:47:03 GMT (95kb)
Title: Diamagnetism versus Paramagnetism in charged spin-1 Bose gases
Authors: Xiaoling Jian, Jihong Qin, and Qiang Gu
Categories: cond-mat.stat-mech cond-mat.quant-gas cond-mat.supr-con
Comments: 6 pages, 5 figures
\\
It has been suggested that either diamagnetism or paramagnetism of Bose
gases, due to the charge or spin degrees of freedom respectively, appears
solely to be extraordinarily strong. We investigate magnetic properties of
charged spin-1 Bose gases in external magnetic field, focusing on the
competition between the diamagnetism and paramagnetism, using the Lande-factor
$g$ of particles to evaluate the strength of paramagnetic effect. We propose
that a gas with $g<{1/\sqrt{8}}$ exhibits diamagnetism at all temperatures,
while a gas with $g>{1/2}$ always exhibits paramagnetism. Moreover, a gas with
the Lande-factor in between shows a shift from paramagnetism to diamagnetism as
the temperature decreases. The paramagnetic and diamagnetic contributions to
the total magnetization density are also calculated in order to demonstrate
some details of the competition.
\\ ( http://arxiv.org/abs/1006.4705 , 95kb)
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arXiv:1006.4720
Date: Thu, 24 Jun 2010 08:42:39 GMT (18kb)
Title: Four-body Efimov effect
Authors: Yvan Castin (LKB - Lhomond), Christophe Mora (LPA), Ludovic
Pricoupenko (LPTMC)
Categories: cond-mat.quant-gas
Comments: 4 pages, 2 figures
\\
We study three same spin state fermions of mass M interacting with a
distinguishable particle of mass m in the unitary limit where the interaction
has a zero range and an infinite s-wave scattering length. We predict an
interval of mass ratio 13.384 < M/m < 13.607 where there exists a purely
four-body Efimov effect, leading to the occurrence of weakly bound tetramers
without Efimov trimers.
\\ ( http://arxiv.org/abs/1006.4720 , 18kb)
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arXiv:1006.4734
Date: Thu, 24 Jun 2010 10:19:26 GMT (2237kb)
Title: Groundstate and Collective Modes of a Spin-Polarized Dipolar
Bose-Einstein Condensate in a Harmonic Trap
Authors: I. Sapina, T. Dahm and N. Schopohl
Categories: cond-mat.quant-gas cond-mat.other
\\
We report new results for the Thomas-Fermi groundstate and the quadrupolar
modes of density oscillations of a spin- polarized dipolar interacting
Bose-Einstein condensate for the case when the external magnetic field is not
orientated parallel to a principal axis of a harmonic anisotropic trap.
\\ ( http://arxiv.org/abs/1006.4734 , 2237kb)
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arXiv:1006.4772
Date: Thu, 24 Jun 2010 12:24:54 GMT (1526kb)
Title: Quantum noise in optical interferometers
Authors: Volodymyr G. Voronov and Michael Weyrauch
Categories: quant-ph gr-qc
Comments: 15 pages, 7 figures
Journal-ref: Phys. Rev. A 81, 053816 (2010)
DOI: 10.1103/PhysRevA.81.053816
\\
We study the photon counting noise in optical interferometers used for
gravitational wave detection. In order to reduce quantum noise a squeezed
vacuum is injected into the usually unused input port. It is investigated under
which conditions the gravitational wave signal may be amplified without
increasing counting noise concurrently. Such a possibility was suggested as a
consequence of the entanglement of the two output ports of a beam splitter. We
find that amplification without concurrent increase of noise is not possible
for reasonable squeezing parameters. Photon distributions for various beam
splitter angles and squeezing parameters are calculated.
\\ ( http://arxiv.org/abs/1006.4772 , 1526kb)
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arXiv:1006.4798
Date: Thu, 24 Jun 2010 14:18:09 GMT (2440kb,D)
Title: Variational calculations on multilayer stacks of dipolar Bose-Einstein
condensates
Authors: Andrej Junginger, J\"org Main, G\"unter Wunner
Categories: cond-mat.quant-gas
Comments: 9 pages, 9 figures
\\
We investigate a multilayer stack of dipolar Bose-Einstein condensates in
terms of a simple Gaussian variational ansatz and demonstrate that this
arrangement is characterized by the existence several stationary states. Using
a Hamiltonian picture we show that in an excited stack there is a coupled
motion of the individual condensates by which they exchange energy. We find
that for high excitations the interaction between the single condensates can
induce the collapse of one of them. We furthermore demonstrate that one
collapse in the stack can force other collapses, too. We discuss the
possibility of experimentally observing the coupled motion and the relevance of
the variational results found to full numerical investigations.
\\ ( http://arxiv.org/abs/1006.4798 , 2440kb)
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arXiv:1006.4817
Date: Thu, 24 Jun 2010 15:39:55 GMT (13kb)
Title: Does one need to consider superconductivity as Bose-Einstein
condensation?
Authors: B.V.Vasiliev
Categories: cond-mat.supr-con
\\
It is shown that the temperature dependence of the value of energy gap in
superconductors can be classified as the order-disorder transition with its
characteristic features. The obtained relationship between the critical
temperature and the critical magnetic field of the condensate of electrically
charged particles is in accordance with measurement data of superconductors.
\\ ( http://arxiv.org/abs/1006.4817 , 13kb)
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arXiv:1005.2203
replaced with revised version Fri, 18 Jun 2010 00:35:37 GMT (53kb)
Title: Bose-Einstein Condensates on slightly asymmetric double-well potentials
Authors: B. Julia-Diaz, J. Martorell, A. Polls
Categories: cond-mat.quant-gas cond-mat.other
Comments: minor labeling corrections, 6 pages, 4 figures
Journal-ref: Phys. Rev. A 81, 063625 (2010)
DOI: 10.1103/PhysRevA.81.063625
\\ ( http://arxiv.org/abs/1005.2203 , 53kb)
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arXiv:0912.5275
replaced with revised version Fri, 18 Jun 2010 09:53:46 GMT (343kb)
Title: Collective modes as a probe of imbalanced Fermi gases
Authors: Jonathan M. Edge, N. R. Cooper
Categories: cond-mat.quant-gas
Comments: 11 pages, 9 figures
Journal-ref: Phys. Rev. A 81, 063606 (2010) [11 pages]
DOI: 10.1103/PhysRevA.81.063606
\\ ( http://arxiv.org/abs/0912.5275 , 343kb)
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arXiv:0907.1757
replaced with revised version Sun, 20 Jun 2010 09:31:03 GMT (10kb)
Title: Free Expansion of a Weakly-interacting Dipolar Fermi Gas
Authors: Takushi Nishimura and Tomoyuki Maruyama
Categories: cond-mat.quant-gas
\\ ( http://arxiv.org/abs/0907.1757 , 10kb)
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arXiv:1006.0734
replaced with revised version Mon, 21 Jun 2010 14:41:39 GMT (76kb)
Title: Quantum phase estimation without a priori knowledge-losses imply shot
noise scaling
Authors: Jan Kolodynski and Rafal Demkowicz-Dobrzanski
Categories: quant-ph
Comments: 4 pages, 2 figures
\\ ( http://arxiv.org/abs/1006.0734 , 76kb)
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arXiv:1003.5873
replaced with revised version Mon, 21 Jun 2010 21:08:28 GMT (23kb)
Title: Bound States and Universality in Layers of Cold Polar Molecules
Authors: J. R. Armstrong, N. T. Zinner, D. V. Fedorov, A. S. Jensen
Categories: cond-mat.quant-gas math-ph math.MP quant-ph
Comments: 6 pages, 5 figures. Revised version to be published
\\ ( http://arxiv.org/abs/1003.5873 , 23kb)
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arXiv:1003.1435
replaced with revised version Tue, 22 Jun 2010 00:57:20 GMT (136kb)
Title: Effective Simulation of Quantum Entanglement Based on Classical Fields
Modulated with Pseudorandom Phase Sequences
Authors: Jian Fu, Shuo Sun, Yingying Xu and Hongtao Dong
Categories: quant-ph
Comments: 5 pages, 2 figures, a minor error corrected
\\ ( http://arxiv.org/abs/1003.1435 , 136kb)
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arXiv:1006.3038
replaced with revised version Tue, 22 Jun 2010 14:25:23 GMT (161kb)
Title: Creation of NOON states by double Fock-state/Bose-Einstein condensates
Authors: W. J. Mullin \and F. Lalo\"{e}
Categories: quant-ph
Comments: 8 pages 5 figures
\\ ( http://arxiv.org/abs/1006.3038 , 161kb)
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arXiv:1006.2324
replaced with revised version Wed, 23 Jun 2010 08:08:02 GMT (243kb)
Title: Self-localization of a small number of Bose particles in a superfluid
Fermi system
Authors: Katarzyna Targonska and Krzysztof Sacha
Categories: cond-mat.quant-gas
Comments: 7 pages, 7 fiqures, improved version
\\ ( http://arxiv.org/abs/1006.2324 , 243kb)
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arXiv:0909.0565
replaced with revised version Thu, 24 Jun 2010 10:05:54 GMT (6936kb)
Title: Spontaneous Magnetic Ordering in a Ferromagnetic Spinor Dipolar
Bose-Einstein Condensate
Authors: Yuki Kawaguchi, Hiroki Saito, Kazue Kudo, and Masahito Ueda
Categories: cond-mat.quant-gas
Comments: Extended version of the previous one; 19 pages, 18 figures
\\ ( http://arxiv.org/abs/0909.0565 , 6936kb)
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arXiv:1005.1158
replaced with revised version Thu, 24 Jun 2010 14:59:54 GMT (26kb)
Title: Temperature and coupling dependence of the universal contact intensity
for an ultracold Fermi gas
Authors: F. Palestini, A. Perali, P. Pieri, G. C. Strinati
Categories: cond-mat.quant-gas
Comments: 5 pages, 5 figures
\\ ( http://arxiv.org/abs/1005.1158 , 26kb)
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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/
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http://www.physics.uq.edu.au/people/mdavis/matts_arXiv/
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