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

Date: Fri, 24 Aug 2007 16:11:38 +1000 (EST)

Date: Fri, 24 Aug 2007 16:11:38 +1000 (EST)

The following message was sent to the matts_arxiv list by Matthew Davis <mdavis_at_physics.uq.edu.au>

Another slow week with 12 new papers and 7 replacements... I guess everyone was

on holiday/at a conference...

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arXiv:0708.1386

Date: Fri, 10 Aug 2007 09:31:58 GMT (232kb)

Title: Quantum computing with collective ensembles of multi-level systems

Authors: E. Brion, K. Moelmer and M. Saffman

Categories: quant-ph

Comments: 4 pages, 4 figures

\\

We propose a new physical approach for encoding and processing of quantum

information in ensembles of multi-level quantum systems, where the different

bits are not carried by individual particles but associated with the collective

population of different internal levels. One- and two-bit gates are implemented

by collective internal state transitions taking place in the presence of an

excitation blockade mechanism which restricts the population of each internal

state to the values zero and unity. 10-20 bit quantum computers can be built

via this scheme in single trapped clouds of ground state atoms subject to the

Rydberg excitation blockade mechanism, and the linear dependence between

register size and the number of internal quantum states in atoms offers

realistic means to reach larger registers.

\\ ( http://arxiv.org/abs/0708.1386 , 232kb)

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arXiv:0708.1390

Date: Fri, 10 Aug 2007 09:54:42 GMT (757kb)

Title: Non-linear optics with two trapped atoms

Authors: Sonia Fern\'andez-Vidal, Stefano Zippilli, and Giovanna Morigi

Categories: quant-ph

Comments: 11 pages, 8 figures

\\

We show theoretically that two atomic dipoles in a resonator constitute a

non-linear medium, whose properties can be controlled through the relative

position of the atoms inside the cavity and the detuning and intensity of the

driving laser. We identify the parameter regime where the system operates as a

parametric amplifier, based on the cascade emission of the collective dipole of

the atoms, and determine the corresponding spectrum of squeezing of the field

at the cavity output. This dynamics could be observed as a result of

self-organization of laser-cooled atoms in resonators.

\\ ( http://arxiv.org/abs/0708.1390 , 757kb)

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arXiv:0708.1743

Date: Mon, 13 Aug 2007 18:07:26 GMT (247kb,D)

Title: Production of long-lived atomic vapor inside high-density buffer gas

Authors: A. O. Sushkov, D. Budker

Categories: physics.atom-ph

\\

Atomic vapor of four different paramagnetic species: gold, silver, lithium,

and rubidium, is produced and studied inside several buffer gases: helium,

nitrogen, neon, and argon. The paramagnetic atoms are injected into the buffer

gas using laser ablation. 50-$\mu$m-diameter wires are used as ablation targets

for gold and silver, bulk targets are used for lithium and rubidium. The buffer

gas cools and confines the ablated atoms, slowing down their transport to the

cell walls. Buffer gas temperatures between 20 K and 295 K, and densities

between $10^{16}$ cm$^{-3}$ and $2\times10^{19}$ cm$^{-3}$ are explored. Peak

paramagnetic atom densities of $10^{11}$ cm$^{-3}$ are routinely achieved. The

longest observed paramagnetic vapor density decay times are 110 ms for silver

at 20 K and 4 ms for lithium at 32 K. The candidates for the limiting

paramagnetic atom loss mechanism are dimer formation and atom loss on sputtered

clusters.

\\ ( http://arxiv.org/abs/0708.1743 , 247kb)

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arXiv:0708.1759

Date: Mon, 13 Aug 2007 19:25:05 GMT (149kb)

Title: Blogging in the physics classroom: A research-based approach to shaping

students' attitudes towards physics

Authors: Gintaras Duda and Katherine Garrett

Categories: physics.ed-ph

Comments: 17 pages, 6 figures

\\

Even though there has been a tremendous amount of research done in how to

help students learn physics, students are still coming away missing a crucial

piece of the puzzle: why bother with physics? Students learn fundamental laws

and how to calculate, but come out of a general physics course without a deep

understanding of how physics has transformed the world around them. In other

words, they get the "how" but not the "why". Studies have shown that students

leave introductory physics courses almost universally less excited about the

topic than when they came in. This paper will detail an experiment to address

this problem: a course weblog or "blog" which discusses real-world applications

of physics and engages students in discussion and thinking outside of class.

Student attitudes towards the value of physics were probed using a 26-question

Likert scale survey over the course of four semesters in an introductory

physics course at a comprehensive Jesuit university. We found that students who

did not participate in the blog study generally exhibited a deterioration in

attitude towards physics as seen previously. However, students who read,

commented, and were involved with the blog maintained their initially positive

attitudes towards physics. Student response to the blog was overwhelmingly

positive, with students claiming that the blog made the things we studied in

the classroom come alive for them and seem much more relevant.

\\ ( http://arxiv.org/abs/0708.1759 , 149kb)

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arXiv:0708.1807

Date: Tue, 14 Aug 2007 05:51:15 GMT (235kb)

Title: Supersolids in the Hard-Core Extended Boson Hubbard Model on the Square

Lattice

Authors: Yu-Chun Chen, Roger Melko, Stefan Wessel, Ying-Jer Kao

Categories: cond-mat.str-el cond-mat.stat-mech

Comments: Revtex 4, 4 pages, 5 figures

\\

We study the ground state phases of the hard-core boson Hubbard model on the

square lattice with both nearest- (nn) and next-nearest-neighbor (nnn) hopping

and repulsion, using quantum Monte Carlo methods. We observe supersolids with

checkerboard, striped, and quarter-filled crystal symmetry, when the system is

doped away from commensurate fillings. We also find that the striped supersolid

transitions directly into the quarter-filled supersolid upon doping. In the

striped supersolid phase, while a strong anisotropy in the superfluid density

is observed, the transverse component remains finite, suggesting a

two-dimensional superflow.

\\ ( http://arxiv.org/abs/0708.1807 , 235kb)

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arXiv:0708.1806

Date: Tue, 14 Aug 2007 05:49:15 GMT (117kb)

Title: Precision Test of Mass Ratio Variations with Lattice-Confined Ultracold

Molecules

Authors: T. Zelevinsky, S. Kotochigova and J. Ye

Categories: physics.atom-ph

Comments: 4 pages, 4 figures

\\

We propose a precision measurement of time variations of the proton-electron

mass ratio using ultracold molecules in an optical lattice. Vibrational energy

intervals are sensitive to changes of the mass ratio. In contrast to

measurements that use hyperfine-interval-based atomic clocks, the scheme

discussed here is model-independent and does not require separation of time

variations of different physical constants. The possibility of applying the

zero-differential-Stark-shift optical lattice technique is explored to measure

vibrational transitions at high accuracy.

\\ ( http://arxiv.org/abs/0708.1806 , 117kb)

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arXiv:0708.1956

Date: Tue, 14 Aug 2007 21:01:18 GMT (37kb)

Title: Transforming squeezed light into large amplitude Schr\"odinger cat

states

Authors: Anne E. B. Nielsen and Klaus M\olmer

Categories: quant-ph

Comments: 6 pages, 4 figures

\\

A quantum superposition of two coherent states of light, a so-called

Schr\"odinger cat, or kitten, state, with small amplitude can be obtained by

subtracting a photon from a squeezed vacuum state. In experiments this

preparation can be made conditioned on the detection of a photon in the field

from a squeezed light source. We propose and analyze an extended measurement

strategy which allows generation of high fidelity cat states with larger

coherent amplitude.

\\ ( http://arxiv.org/abs/0708.1956 , 37kb)

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arXiv:0708.2073

Date: Wed, 15 Aug 2007 17:19:17 GMT (647kb)

Title: Controlled exchange interaction between pairs of neutral atoms in an

optical lattice

Authors: M. Anderlini, P. J. Lee, B. L. Brown, J. Sebby-Strabley, W. D.

Phillips, J. V. Porto

Categories: quant-ph

Journal-ref: Nature 448, 452-456 (2007)

DOI: 10.1038/nature06011

\\

Ultra-cold atoms trapped by light, with their robust quantum coherence and

controllability, provide an attractive system for quantum information

processing and for simulation of complex problems in condensed matter physics.

Many quantum information processing schemes require that individual qubits be

manipulated and deterministically entangled with one another, a process that

would typically be accomplished by controlled, state-dependent, coherent

interactions among qubits. Recent experiments have made progress toward this

goal by demonstrating entanglement among an ensemble of atoms confined in an

optical lattice. Until now, however, there has been no demonstration of a key

operation: controlled entanglement between atoms in isolated pairs. We have

used an optical lattice of double-well potentials to isolate and manipulate

arrays of paired atoms, inducing controlled entangling interactions within each

pair. Our experiment is the first realization of proposals to use controlled

exchange coupling in a system of neutral atoms. Although 87Rb atoms have nearly

state-independent interactions, when we force two atoms into the same physical

location, the wavefunction exchange symmetry of these identical bosons leads to

state-dependent dynamics. We observe repeated interchange of spin between atoms

occupying different vibrational levels, with a coherence time of more than ten

milliseconds. This observation represents the first demonstration of the

essential component of a quantum SWAP gate in neutral atoms. The "half

implementation" of SWAP, the sqrt(SWAP) gate, is entangling, and together with

single qubit rotations form a set of universal gates for quantum computation.

\\ ( http://arxiv.org/abs/0708.2073 , 647kb)

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arXiv:0708.2107

Date: Wed, 15 Aug 2007 21:15:54 GMT (225kb)

Title: Quantum glass phases in the disordered Bose-Hubbard model

Authors: Pinaki Sengupta and Stephan Haas

Categories: cond-mat.dis-nn

Journal-ref: Phys. Rev. Lett. 99, 050403 (2007)

\\

The phase diagram of the Bose-Hubbard model in the presence of off-diagonal

disorder is determined using Quantum Monte Carlo simulations. A sequence of

quantum glass phases intervene at the interface between the Mott insulating and

the Superfluid phases of the clean system. In addition to the standard Bose

glass phase, the coexistence of gapless and gapped regions close to the Mott

insulating phase leads to a novel Mott glass regime which is incompressible yet

gapless. Numerical evidence for the properties of these phases is given in

terms of global (compressibility, superfluid stiffness) and local

(compressibility, momentum distribution) observables.

\\ ( http://arxiv.org/abs/0708.2107 , 225kb)

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arXiv:0708.2128

Date: Thu, 16 Aug 2007 03:41:57 GMT (412kb)

Title: Self-Trapping of Bose-Einstein Condensates in an Optical Lattice: the

Effect of the System Dimension

Authors: Ju-Kui Xue, Ai-Xia Zhang, Jie Liu

Categories: cond-mat.mes-hall

Comments: 8pages, 9 figures

\\

In the present paper, we investigate the dynamics of a Bose-Einstein

condensates (BEC) loaded into an deep optical lattice of 1D, 2D and 3D, both

analytically and numerically. We focus on the self-trapping state and the

effect of the system dimension. Under the tight-binding approximation we obtain

an analytical criterion for the self-trapping state of BEC using time-dependent

variational method. The phase diagram for self-trapping, soliton, breather, or

diffusion of the BEC cloud is obtained accordingly and verified by directly

solving the discrete Gross-Pitaevskii equation (GPE) numerically. In

particular, we find that the criterion and the phase diagrams are modified

dramatically by the dimension of the lattices.

\\ ( http://arxiv.org/abs/0708.2128 , 412kb)

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arXiv:0708.2196

Date: Thu, 16 Aug 2007 13:22:54 GMT (585kb)

Title: Superfluid Dynamics of a Bose-Einstein Condensate in a Quantum Optical

Lattice

Authors: Aranya B Bhattacherjee

Categories: cond-mat.stat-mech

Comments: 12 pages, 10 figures

\\

We study the effect of a one dimensional optical lattice in a cavity field

with quantum properties on the superfluid dynamics of a Bose-Einstein

condensate(BEC). In the cavity the influence of atomic backaction and the

external driving pump become important and strongly modify the optical

potential. Due to the strong coupling between the condensate wavefunction and

the cavity modes, the cavity light field develops a band structure. This study

reveals that the pump and the cavity emerges as a new handle to control the

superfluid properties of the BEC.

\\ ( http://arxiv.org/abs/0708.2196 , 585kb)

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arXiv:0708.2234

Date: Thu, 16 Aug 2007 16:00:32 GMT (5kb)

Title: Bose-Einstein condensation of a Knudsen gas

Authors: Kersion Huang

Categories: cond-mat.stat-mech

Comments: 5 pages

\\

We reconcile a long-standing controversy regarding the transition temperature

of the Bose-Einstein condensation in a dilute interacting Bose gas, by showing

that there is a crossover between ideal gas and interacting gas. The former

corresponds to a Knudsen (or collisionless) regime, in which the mean-free-path

is much larger than the system dimension, while the latter corresponds to the

opposite hydrodynamic regime. The deviation of the transition temperature from

that of the non-interacting gas is proportional to the square root of a in the

Knudsen regime, and to a in the hydrodynamic regime, where a is the scattering

length. This crossover may be observable in a Bose gas trapped in a potential

or on an optical lattice.

\\ ( http://arxiv.org/abs/0708.2234 , 5kb)

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The replacements:

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arXiv:cond-mat/0305614

replaced with revised version Fri, 10 Aug 2007 05:29:02 GMT (102kb)

Title: Quantum gas-liquid condensation in an attractive Bose gas

Authors: Shun-ichiro Koh

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

Comments: 12 pages, 8 figures

Journal-ref: Physical Review E 72,016104(2005)

DOI: 10.1103/PhysRevE.72.016104

\\ ( http://arxiv.org/abs/cond-mat/0305614 , 102kb)

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arXiv:quant-ph/0602025

replaced with revised version Fri, 10 Aug 2007 09:08:16 GMT (226kb)

Title: Macroscopic superpositions of superfluid flows

Authors: David W. Hallwood, Jacob Dunningham, Keith Burnett

Categories: quant-ph

Comments: 5 pages, 4 figures

Journal-ref: New J. Phys. 8 (2006) 180

\\ ( http://arxiv.org/abs/quant-ph/0602025 , 226kb)

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arXiv:cond-mat/0611689

replaced with revised version Mon, 13 Aug 2007 17:47:14 GMT (99kb)

Title: Probing $n$-Spin Correlations in Optical Lattices

Authors: Chuanwei Zhang, V. W. Scarola, and S. Das Sarma

Categories: cond-mat.str-el cond-mat.other quant-ph

Comments: 7 pages, 4 figures

Journal-ref: Phys. Rev. A. 76, 023605 (2007)

DOI: 10.1103/PhysRevA.76.023605

\\ ( http://arxiv.org/abs/cond-mat/0611689 , 99kb)

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arXiv:cond-mat/0612174

replaced with revised version Sat, 11 Aug 2007 20:42:41 GMT (378kb)

Title: Phase-locking transition of coupled low-dimensional superfluids

Authors: L. Mathey, A. Polkovnikov, and A.H. Castro Neto

Categories: cond-mat.other

Comments: 7 pages, 4 figures, extended discussion

\\ ( http://arxiv.org/abs/cond-mat/0612174 , 378kb)

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arXiv:cond-mat/0305669

replaced with revised version Tue, 14 Aug 2007 06:06:12 GMT (67kb)

Title: Meissner effect in a charged Bose gas with short-range repulsion

Authors: Shun-ichiro Koh

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

Comments: 8 pages, 3 figures

Journal-ref: Physical Review B 68,144502(2003)

DOI: 10.1103/PhysRevB.68.144502

\\ ( http://arxiv.org/abs/cond-mat/0305669 , 67kb)

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arXiv:cond-mat/0609374

replaced with revised version Tue, 14 Aug 2007 12:15:47 GMT (448kb)

Title: Bose-Einstein Condensation Temperature of Dipolar Gas in Anisotropic

Harmonic Trap

Authors: Konstantin Glaum, Axel Pelster

Categories: cond-mat.stat-mech

Comments: Author information under

http://www.theo-phys.uni-essen.de/tp/ags/pelster_dir

Journal-ref: Physical Review A 76, 023604 (2007)

\\ ( http://arxiv.org/abs/cond-mat/0609374 , 448kb)

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arXiv:0705.0671

replaced with revised version Tue, 14 Aug 2007 15:38:58 GMT (54kb)

Title: BEC-BCS Crossover of a Trapped Two-Component Fermi Gas with Unequal

Masses

Authors: J. von Stecher, C. H. Greene, D. Blume

Categories: cond-mat.other

Comments: 11 pages, 6 figures, extended version

\\ ( http://arxiv.org/abs/0705.0671 , 54kb)

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arXiv:0706.4260

replaced with revised version Tue, 14 Aug 2007 11:26:31 GMT (346kb)

Title: Ultracold Bose gases in time-dependent 1D superlattices: response and

quasimomentum structure

Authors: Markus Hild, Felix Schmitt, Ilona T\"urschmann, Robert Roth

Categories: cond-mat.stat-mech

Comments: 4 pages, 4 figures

\\ ( http://arxiv.org/abs/0706.4260 , 346kb)

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-- ========================================================================= Dr M. J. Davis, Senior Lecturer in Physics School of Physical Sciences, email: mdavis_at_physics.uq.edu.au University of Queensland, ph : +61 7 334 69824 Brisbane, QLD 4072, fax : +61 7 336 51242 Australia. http://www.physics.uq.edu.au/people/mdavis/ ========================================================================= Matt's arXiv selection: weekly summary of cold-atom papers from arXiv.org http://www.physics.uq.edu.au/people/mdavis/matts_arXiv/ ========================================================================= Legal stuff: Unless stated otherwise, this e-mail represents only the views of the sender and not the views of the University of Queensland =========================================================================Received on Fri Aug 24 2007 - 16:11:38 EST

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