Quantum Degenerate Gases in Low-Dimensionality

October 4-6, 2004

Brett Esry, Maxim Olshanii, Joerg Schmiedmayer

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Anderson

Blume

Bromley

Cazalilla

Esslinger

 Fertig

Fortágh 

 Granger

 Hadzibabic

Haldane 

Krüger 

Lieb 

Bergeman

Nägerl

Oberthaler

Olshanii

Demler

Petrov 

Pritchard 

Rubinsztein-Dunlop

Thywissen 

Vasiliev

Weiss 

 Yurovsky

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Workshop Participants

INVITED SPEAKERS

Prof Dana Z. Anderson
JILA
University of Colorado 440
Boulder, CO 80309
dana@jila.colorado.edu
Prof. Doerte Blume
Department of Physics
Washington State University
Pullman, WA 99164-2814
doerte@wsu.edu
Dr. Michael Bromley
Kansas State University
116 Cardwell Hall
Manhattan, KS 66506
bromley@phys.ksu.edu
Dr. Miguel A. Cazalilla
Donostia Intl Physics Center
Manuel de Lardizabal, 4
San Sebastian, E-20018 Spain
waxcagum@sq.ehu.es
Prof. Eugene Demler
Physics Department
Harvard University
Cambridge, MA 02138
demler@cmt.harvard.edu
Prof. Brett Esry
Kansas State University
Physics Department
116 Cardwell Hall
Manhattan, KS 66502
esry@phys.ksu.edu
Prof. Tilman Esslinger
ETH Zurich
HPF D 4, Hoenggerberg
Zurich, 8093, Switzerland
esslinger@phys.ethz.ch
tilman.esslinger@iqe.phys.ethz.ch
Dr. Chad Fertig
NIST
100 Bureau Drive
MS 8424
Gaithersburg, MD 20878
chad.fertig@nist.gov
Dr. József Fortágh
University of Tuebingen
Auf der Morgenstelle 14
72076 Tuebingen, Germany
fortagh@pit.physik.uni-tuebingen.de
Dr. Brian E. Granger
Santa Clara University
500 El Camino Real
312 Daly Science
Santa Clara, CA 95053
bgranger@scu.edu
Dr. Zoran Hadzibabic
Laboratoire Kastler Brossel
Ecole Normale Superieure
Paris, 75005 France
Zoran@lkb.ens.fr
Prof. F. Duncan M. Haldane
Princeton University
Physics Department
Jadwin Hall
Princeton, NJ 08544-0708
haldane@princeton.edu
Dr. Peter Krüger
Physikalisches Institut
University of Heidelberg
Philosophenweg 12
69120 Heidelberg, Germany
krueger@physi.uni-heidelberg.de
Prof. Elliott H. Lieb
Princeton University
Jadwin Hall
P.O. Box 708
Princeton, NJ 08544-0708
lieb@princeton.edu
Prof. Michael G. Moore
Ohio University
251 Clippinger Lab
Department of Physics Astronomy
Athens, OH 45701
moorem@ohiou.edu
Dr. Hanns-Christoph Nägerl
University of Innsbruck
Technikerstrasse 25/4
Inst. fuer Experimentalphysik
Innsbruck 6020 Austria
christoph.naegerl@uibk.ac.at
Prof. Markus Oberthaler
University of Heidelberg
INF 227
Heidelberg, 69110 Germany
oberthaler@kip.uni-hd.de
Prof. Maxim Olshanii
Department of Physics and Astronomy
University of Southern California
Los Angeles, CA 90089
olshanii@physics.usc.edu
Dr. Belén Paredes
Max-Planck-Institut für Quantenoptik
Hans-Kopfermann-Str. 1
D-85748 Garching, Germany
Belen.Paredes@mpq.mpg.de
Dr. Dmitry Petrov
ITAMP
60 Garden Street, MS 14
Cambridge, MA 02138
dpetrov@cfa.harvard.edu
Prof. David E. Pritchard
Room 26-237
77 Massachusetts Avenue
Massachusetts Institute of Technology
Cambridge, MA 02139-4307
dpritch@mit.edu
Prof. Halina Rubinsztein-Dunlop
University of Queensland
Physics Department
S. Lucia QLD, 4072, Australia
halina@physics.uq.edu.au
Prof. Jörg Schmiedmayer
Univ. of Heidelberg
Philosophenweg 12
D69120 Heidelberg, Germany
schmiedmayer@atomchip.org
Prof. Joseph Thywissen
University of Toronto
60 Saint George Street
Toronto, ON, M5S1A7 Canada
jht@physics.utoronto.ca
Dr. Sergey Vasiliev
Department of Physics
University of Turku
Turku, 20014 Finland
servas@utu.fi
Prof. David S. Weiss
Penn State University
104 Davey Lab
University Park, PA 16802
dsweiss@phys.psu.edu
Dr. Vladimir Yurovsky
Tel Aviv University
Ramat Aviv
Tel Aviv, 69978 Israel
volodia@post.tau.ac.il

 

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Workshop Schedule

Monday, October 4, 2004

Phillips Auditorium (all day)
8:45-9:00 a.m. WELCOME

One-Dimensional Gases
9:00-9:40 a.m. D. Pritchard:  New Approaches to Confined Atom Interferometers
9:40-10:20 a.m. D. Blume: Temperature-Dependent Study of Bose Gases: Crossover from Three- to One-Dimensional Behavior
 10:20-10:50 a.m. Coffee
 10:50-11:30 a.m. M. Olshanii:  Interactions and Interference: Beyond Mean-Field
 11:30-12:10 p.m.  E. Lieb: Rigorous Results on Bose Gases in Various Dimensions
12:10-12:50 p.m.  M. Bromley: Manipulation of Matter Waves Using Periodic Potentials
 12:50-2:20 p.m.  Lunch

 Strongly Correlated Systems
 2:20-3:00 p.m. D.  Haldane: Nematic States of Quantum Spin Chains and Optically-Trapped Spin-1 Bosons
 3:00-3:40 p.m. B. Paredes: Tonks-Girardeau Gas in an Optical Lattice
 3:40-4:10 p.m.  Coffee
 4:10-4:50 p.m. E. Demler:  Boson-fermion mixtures in optical lattices
4:50-5:30 p.m. M. Cazalilla: Atomic Luttinger Liquids and Fermionized Bose Gases
 5:30-6:30 p.m. Reception in Perkin Lobby

Tuesday, October 5, 2004

Phillips Auditorium (all day)

Low-dimensional Experiments

 9:00-9:40 a.m.  M. Oberthaler:  Nonlinear Wave Dynamics in One Dimensional Periodic Potentials
 9:40-10:20 a.m.  Z. Hadzibabic: An Array of 2D Bose-Einstein Condensates in an Optical Lattice
 10:20-10:50 a.m. Coffee
 10:50-11:30 a.m.  H. Nägerl:  A Two-Dimensional Bose-Einstein Condensate in an Optical Surface Trap
 11:30-12:10 p.m.  H. Rubinsztein-Dunlop:  Bose-Einstein Condensates on an Atom Chip
 12:10-12:50 p.m.  J. Thywissen: Towards Ultracold Fermions on a Chip
 12:50-2:20 p.m. Lunch

 Scattering in Waveguides

 2:20-3:00 p.m. M. Moore: Scattering in Tight Atom Waveguides and Confinement Induced Resonances
 3:00-3:40 p.m. B. Granger: Strongly Interacting Spin-Polarized Fermions in Quasi-1D Traps
 3:40-4:10 p.m. Coffee
 4:10-4:50 p.m. D. Petrov:  Interparticle Interaction in Quasi-2d Gases and Prospects for Bcs Transition
 4:50-5:30 V. Yurovsky:  Effect of Feshbach Resonances on Collisions in Atomic Waveguides

 

Wednesday, October 6, 2004

Phillips Auditorium (all day)

 Tonks-Girardeau and Kosterlitz-Thouless

 9:00-9:40 a.m. Weiss: Observation of a 1D Tonks-Girardeau gas
9:40-10:20 a.m. Esslinger:  Quantum Degenerate Gases in Optical Lattices
 10:20-10:50 a.m. Coffee
10:50-11:30 a.m. C. Fertig: Transport Studies of a 1D Bose Gas in a 1D Optical Lattice
 11:30-12:10 p.m.
S. Vasiliev: Experiments with Dense 2D Atomic Hydrogen Gas on Liquid Helium Surfaces
 12:10-1:10 p.m. Lunch (early and short)

Atom Guides and Applications

 1:10-1:50 p.m. D. Anderson: BEC Waveguide Michelson Interferometer on a Chip
 1:50-2:30 p.m. P. Krüger: Towards 1d Experiments on Atom Chips
 2:30-3:10 p.m. J. Fortágh:  Bose-Einstein Condensates in Tailored Micro-Potentials
 3:10 p.m. Adjourn

 

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Abstracts

Anderson

Blume

Bromley

Cazalilla

Esslinger

 Fertig

Fortágh 

 Granger

 Hadzibabic

Haldane 

Krüger 

Lieb 

Moore

Nägerl

Oberthaler

Olshanii

Paredes

Petrov 

Pritchard 

Rubinsztein-Dunlop

Thywissen 

Vasilyev

Weiss 

 Yurovsky

 BEC Waveguide Michelson Interferometer on a Chip

Dana Z. Anderson,1 Victor M. Bright,2 Eric Cornell,1 Quentin Diot,1 Mara Prentiss,3 Stephen R. Segal,1 Ying-Ju Wang,1 and Saijun Wu3

1Department of Physics and JILA, University of Colorado and National Institute of Standards and Technology, University JILA UCB 440, Boulder CO 80309-0440
2Department of Mechanical Engineering, University of Colorado, Boulder, CO 80309
3Department of Physics, Harvard University, Cambridge, MA, 02138

PDF Version

An atom Michelson interferometer is formed using a 1-dimensional waveguide configuration. Atoms are trapped and cooled in a pyramid MOT, then transported to a Ioffe-Pritchard trap where they undergo further cooling but remain above the critical temperature for the formation of a Bose-Einstein condensate. The cooled atoms are then launched towards and captured on an atom chip. The magnetic waveguide and other atom manipulation structures on the chip are produced by current-carrying wires lithographically patterned on the chip substrate. A one-dimensional waveguide is formed by a current in one of the central wires acting in conjunction with a bias magnetic field. Mounted on the chip is a pair of prism-shaped mirrors. Atoms are transported through a small tunnel lying underneath the first prism to the approximate center of the atom waveguide region between the mirrors, where they are again trapped, then evaporatively cooled to form a condensate. The two mirrors are arranged to form a standing light wave, which lies parallel to and directly above the waveguide conductor. The atoms sitting within the waveguide can thus be subject to the standing light field.

The initial condensate is split into two, oppositely directed atom clouds of momenta by exposing the cloud to a double-pulse standing light field. After a propagating a short time, the atoms are exposed to an optical "Bragg" pulse, which reverses their momentum. The atoms thus return to their starting point, where they are finally exposed to a second double-pulse. Thus the three exposures of light serve to split, reflect, and recombine the atoms. Upon re-combination the atoms generally form three clouds: a zero-momentum ( ) cloud, and a pair of oppositely directed non-zero ( ) clouds.

The atom optical path length between the initial two propagating atom clouds is varied either by varying a magnetic gradient along the waveguide direction, or by giving the initial condensate cloud an initial velocity. We observe interference in the final atom cloud configuration by comparing the population of the zero-momentum cloud with the two non-zero momentum cloud as a function of the relative phase difference. The interference contrast is seen to be excellent out to approximately 4 ms. For times on the order of 10 ms, however, the interference contrast falls to about 20%, indicating either a real or apparent loss of atomic coherence.

We describe further details of the experiment, and make some speculations regarding the observed loss of coherence.

 

Temperature-Dependent Study of Bose Gases: Crossover from Three- to One-Dimensional Behavior

D. Blume and Kwangsik Nho

Department of Physics
Washington State University
Pullman, WA 99164-2814
 

Abstract PDF

 Manipulation of Matter Waves Using Periodic Potentials*

M.W.J. Bromley, B.D. Esry

Department of Physics
Kansas State University
Manhattan, KS 66506

Using a combination of Bose-Einstein condensates and moving optical lattices, experimentalists have recently demonstrated the manipulation of the dispersion of a matter wave during expansion [1,2].

We consider whether it is possible to exert similar control over a wavepacket during propagation through a static periodic potential of finite length. A 1-D waveguide model neglecting atom-atom interactions is used to characterize the effective mass of matter waves propagating through various periodic potential structures. It is seen that to vary the effective mass requires periodic potentials that are relatively strong compared to the transverse waveguide confining potential, while methods of loading/unloading into/out of the finite length 1-D potentials are explored.

* This research was supported by the Department of the Navy, Office of Naval Research, and in part by the Research Corporation.

[1] B.Eiermann et.al Phys. Rev. Lett. 91 060402 (2003)
[2] L.Fallani et.al Phys. Rev. Lett. 91 240405 (2003)

 

Atomic Luttinger Liquids and Fermionized Bose Gases

Miguel A. Cazalilla

Donostia Intl Physics Center
Manuel de Lardizabal, 4
San Sebastian, E-20018 Spain

In this talk, we discuss the correlation properties of one-dimensional Bose gases. Finite-size effects on the momentum distribution will be illustrated by considering a model of bosons (a Luttinger liquid) in a box. We shall also touch upon the differences between the momentum distribution of a weakly interacting and a strongly interacting 1D Bose gas at finite temperature. Finally, the different properties of strongly interacting Bose gases in the continuum and on the lattice will be described.

 Quantum Degenerate Gases in Optical Lattices

Tilman Esslinger

ETH Zürich
Quantenelektronik
HPF D 4, Hönggerberg
CH-8093 Zürich, Switzerland

Quantum gases trapped in the periodic potential of an optical lattice have opened a new experimental window on many-particle quantum physics. The observation of the quantum phase transition from a superfluid to a Mott insulating phase in a Bose gas has offered a first glimpse into the physics which is now becoming experimentally accessible. I will discuss experiments with one-dimensional Bose gases and report on first results with a Fermi gas loaded into a three-dimensional optical lattice.

 

 Transport Studies of a 1D Bose Gas in a 1D Optical Lattice

Dr. Chad Fertig

Laser Cooling and Trapping Group
National Institute of Standards and Technology
100 Bureau Drive, Stop 8424
Gaithersburg, MD 20899-8424

I will report on experimental studies of transport in a trapped 1D Bose gas. We realize a 1D Bose gas by partitioning a magnetically-trapped BEC into an array of independent "tubes'' using a deep 2D optical lattice. Dipole oscillations along the tubes are excited in the presence of a 1D axial "corrugating" lattice. Surprisingly, small amplitude oscillations are strongly damped for extremely shallow depths of the corrugating lattice. This behavior is in striking contrast to previous observations of undamped oscillations in 3D BEC systems. For deeper corrugating lattices, the motion becomes strongly over-damped, having a time to return to equilbrium that can be orders of magnitude longer than characteristic timescale for tunneling in the lattice. We also probe the momentum distribution of the atoms, and find that, remarkably, the extreme inhibition of transport is not accompanied by band-filling.

 Bose-Einstein Condensates in Tailored Micro-Potentials

József Fortágh

Physikalisches Institut der Universität Tübingen
72076 Tübingen, Germany

Bose-Einstein condensates in tailored micro-potentials are bringing closer the realization of integrated coherent atom optics on a chip. Conceivable are matter wave interferometers for ultra-sensitive force detection or even quantum bits for quantum information processing.

Current experiments concentrate on the control of Bose-Einstein condensates using basic atom optical elements. Recent studies demonstrate several perspectives and limitations of this technology.

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Strongly Interacting Spin-Polarized Fermions in Quasi-1D Traps

Brian E. Granger
 
Santa Clara University
500 El Camino Real
312 Daly Science
Santa Clara, CA 95053

When confined to quasi-one-dimensional (1D) geometries, spin-polarized fermions can have strong effective 1D interactions. This opens up the possibility of studying a fermionic version of the Tonks-Girardeau gas of impenetrable bosons. In this novel 1D many body system, recently introduced by a number of groups, strongly interacting 1D fermions are dual to noninteracting 1D bosons. In this talk I will describe both the two particle scattering physics leading to these strong effective 1D interactions and the single particle correlations that these interactions create in the many body system.

 

An Array of 2D Bose-Einstein Condensates in an Optical Lattice

Zoran Hadzibabic

Laboratoire Kastler Brossel
Ecole Normale Superieure
Paris, 75005 France

I will discuss our studies of an array of two-dimensional 87Rb Bose-Einstein condensates, created in a one-dimensional optical lattice. Our lattice potential has a long period, of several microns, which allows for a large number of atoms (~104) to be loaded into each site, and for the condensates to be completely isolated from each other.

We have studied matter wave interference in this system, and have observed high-contrast interference between 30 condensates with uncorrelated phases [1]. Our observations are quantitatively explained with a simple theoretical model which generalizes the analysis of the interference of two independent condensates.

I will also discuss the possibilities for creating a single two-dimensional condensate in this setup.

[1] Z. Hadzibabic, S. Stock, B. Battelier, V. Bretin, and J. Dalibard, quant-ph/0405113.

 

 

Nematic States of Quantum Spin Chains and Optically-Trapped Spin-1 Bosons

F. D. M. Haldane

Department of Physics
Princeton University
Princeton NJ 08544-0708

The Mott insulator states of optically-trapped spin-1 bosonic atoms on a one-dimensional lattice with an odd number of atoms per well provides a new physical realization of the spin-1 quantum spin chain. In the absence of exchange splitting between the spin-0 and spin-2 two-particle scattering cross-sections, the system has SU(3) symmetry, corresponding to exactly equal-strength "Heisenberg" and "biquadratic" exchange in the AKLT parameterization of the spin-1 chain. Exchange splitting allows a physical realization of the model in a previously-inaccessible parameter region. There has been controversy about the competition between nematic order and spontaneous dimerization in the spin-1 chain. I will show how this is resolved using a nematic non-linear sigma model field-theory description: local nematic correlations immediately lead to dimerization of odd-integer spin chains. If time permits, other aspects of one-dimensional physics that could be realized in optical traps will be reviewed.

 

Towards 1d Experiments on Atom Chips

Peter Krüger

Physikalisches Institut
University of Heidelberg
Philosophenweg 12
69120 Heidelberg, Germany

Cold neutral atoms can be controlled and manipulated in microscopic potentials near surfaces of atom chips. These integrated micro-devices combine the known techniques of atom optics with the capabilities of well established micro- and nanofabrication technology.

We use current and charge carrying structures to form complex potentials with high spatial resolution only microns from the surface. In particular, atoms can be confined to an essentially one-dimensional motion, i.e. the temperature of a cloud can be smaller than the transverse energy level spacing of the potential. In the case of a Bose-Einstein condensate (BEC), the transverse ground state energy can exceed the chemical potential of the BEC.

In this talk, we will give an overview of our experiments studying the manipulation of both thermal atoms and BECs on atom chips. First experiments in the quasi one-dimensional regime will be presented. These experiments profit from strongly reduced residual disorder potentials caused by imperfections of the chip fabrication with respect to previously published experiments. This is due to our purely lithographic fabrication technique that proves to be advantageous over electroplating. We have used one dimensionally confined BECs as an ultra-sensitive probe to characterize these potentials. These smooth potentials allow us to explore various aspects of the physics of degenerate quantum gases in low dimensions.

 

Rigorous Results on Bose Gases in Various Dimensions

Elliott H. Lieb

Princeton University
Jadwin Hall
P.O. Box 708
Princeton, NJ 08544-0708

I will give a brief survey of work that has been going on for the past 6 years, mostly on ground states of Bose gases, with various collaborators (Aizenman, Seiringer, Solovej, Yngvason).

These include:
1.) The asymptotic ground state energy of dilute homogeneous gases in 3 and in 2 dimensions.
2.) Proof that the Gross-Pitaevskii equation is correct in this limit for trapped gases.
3.) The existence of 100% Bose-Einstein condensation and 100% superfluidity in this limit.
4.) The verification of Foldy's formula for high density jellium and of Dyson's conjecture for the 2-component charged Bose gas in 3D.
5.) Proof of the transition from 3D to 1D behavior (Lieb-Liniger model) for 3D bosons in long traps.
6.) A model for an optical lattice that displays true quenching of BEC for interacting bosons when the lattice is "deep" enough. (Phys. Rev. A 70, 023612 (2004)).

 Scattering in Tight Atom Waveguides and Confinement Induced Resonances

Michael G. Moore

Ohio University
Department of Physics Astronomy
Athens, OH 45701

Recent work will be presented on the use of zero-range models to study low-energy scattering under tight transverse confinement. The effects of confinement on atom-atom scattering can be investigated via a Green's function, developed by A. Lupu-Sax, where the Green's function of the confinement potential, and the low-energy behavior of the free-space T-matrix of the scatterer are the only inputs. The approach allows the calculation of multi-channel 1-d scattering amplitudes, from which the complete Kinetic coefficients can be determined. In addition, the appearance of Confinement induced resonances, and their interpretation as a type of Feshbach resonance will be presented, as well as the influence of the confinement on near-threshold bound states.

 

A Two-Dimensional Bose-Einstein Condensate in an Optical Surface Trap

B. Engeser, D. Rychtarik, Hanns-Christoph Nägerl, and Rudolf Grimm
Institut für Experimentalphysik, Technikerstraße 25, Universität Innsbruck, 6020 Innsbruck, Austria

Phone: +43-512-507 6316, , FAX: +43-512-507 2921, email: Christoph.Naegerl@uibk.ac.at

We create a single two-dimensional Bose-Einstein Condensate of Cesium atoms by evaporative cooling in a highly anisotropic surface trap [1]. Our gravito-optical surface trap is based on a horizontal evanescent-wave atom mirror in combination with a horizontally confining optical dipole potential. The pancake-shaped condensate of a few thousand atoms with an aspect ratio of 50:1 is produced 4 micrometers above the dielectric surface. We detect the formation of the condensate either by a release-and-recapture technique along the horizontal direction or alternatively by inducing a collapse of the condensate at negative scattering lengths.

The condensate will now allow us to study the effects of reduced dimensionality on the spectrum of collective excitations and on the behavior and stability of vortices. For vanishing scattering lengths it could be possible to detect the anisotropy of the dipole-dipole interaction. Further, an optical surface lattice could be created through the interference of two or more evanescent waves to produce individual one-dimensional traps to study the Tonks-Girardeau limit of an interacting Bose system.

References
1. D. Rychtarik, B. Engeser, H.-C. Nägerl, and R. Grimm, Phys. Rev. Lett. 92, 173003 (2004)

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Nonlinear Wave Dynamics in One Dimensional Periodic Potentials

Thomas Anker, Michael Albiez, Bernd Eiermann, Rudolf Gati, Stephan Hunsmann, Markus Oberthaler

Kirchhoff-Institut für Physik
Universität Heidelberg
Im Neuenheimer Feld 227
69120 Heidelberg

Nonlinear matter wave dynamics in one­dimensional periodic potentials is very diverse. In this talk we will present our experimental results on two different wave phenomena leading to the formation of non-spreading wave packets.

The first part of the talk is devoted to the first realization of atomic gap solitons of 87Rb [1]. In this experiment we utilize a weak periodic potential to realize anomalous matter wave dispersion, which can be described with an effective negative mass. This allows the realization of bright solitons although the atom-atom interaction is repulsive. Since our experiment is carried out in the quasi-one-dimensional regime, the observations are in very good agreement with the predictions of a simple one-dimensional model.

We will also present our first results on the propagation of nonlinear matter waves in the regime with moderate atomic densities and deep periodic potentials. Here the dynamics is conveniently described by looking at the atomic tunnelling current from well to well. One prominent effect due the atom-atom interaction is the possibility that a sufficiently high density difference between two wells can prevent further tunnelling and thus halts the wave packet dynamics - an effect called "macroscopic quantum self trapping"[2].

[1] B. Eiermann et al., Phys. Rev. Lett. 92, 230401 (2004).
[2] A. Trombettoni and A. Smerzi, Phys. Rev. Lett. 86, 2353 (2001).

 Interactions and Interference: Beyond Mean-Field

Maxim Olshanii

Department of Physics and Astronomy
University of Southern California
Los Angeles, CA 90089

In collaboration with Marvin Girardeau, Vanja Dunjko, Hieu Nguyen,
Marc Jeffrey, and Kunal Daas.

Parameters of the recent experiments with single-mode one-dimensional atom traps (NIST, ETHZ, PennState) belong to the domain of strong correlations with the quantum degeneracy parameter ranging from .5 to 5. Thus a non-perturbative, beyond-mean-field approach is needed to address the questions of interaction-induced limitations on performance of the future wave-guide-based interferometers.

In this presentation I will describe two gedanken experiments, the first being related to the Ramsey-Borde interferometric scheme, while the second to the Young's one. Both models constitute non-integrable extensions of the integrable Lieb-Liniger model, and thus allow for a non-perturbative treatment. The first process is a half-cycle of the adiabatic population inversion between two guides, with an immediate interferometric reading in the end. The second scheme deals with the emergence of interference fringes after a phase imprinting pulse.

The probably dominant effect of interactions -- degradation of coherence between splitting and recombination -- still remains an intractable problem. I will further discuss several two-body models describing interaction of mutually interacting atoms with interferometric elements: solutions generated by these models indicate the potential difficulties in treating the many-body case.

In all cases described above the primary object of interest is the relationship between the fringe visibility and degree of quantum degeneracy.

 

Tonks-Girardeau Gas in an Optical Lattice

Belén Paredes

Max-Planck-Institut für Quantenoptik
Hans-Kopfermann-Str. 1
D-85748 Garching, Germany

I will report on our recent work on the preparation of a Tonks-Girardeau gas in an optical lattice. I will discuss the experimental realization as well as the theoretical approach based on fermionization that we have developed to describe the finite-inhomogeneous-finite-temperature Tonks-Girardeau gas observed in the experiment.

I will finally briefly discuss our recent ideas regarding the efficient simulation of random systems.

 Interparticle Interaction in Quasi-2d Gases and Prospects for Bcs Transition

D.S. Petrov, M.A. Baranov, and G.V. Shlyapnikov

ITAMP
60 Garden Street, MS 14
Cambridge, MA 02138

Recent progress in trapping and cooling of neutral atoms allows one to tightly confine the particle motion in one direction to zero point oscillations and thus create the gas which is kinematically two-dimensional. The interparticle interaction has then a quasi-2D character and depends logarithmically on the relative energy of colliding particles. We analyse the s-wave scattering in this quasi-2D regime and find that the scattering amplitude and, hence, the interaction strength are sensitive to the frequency of the tight confinement.

The creation of quasi-2D Fermi gases will open new handles on achieving the superfluid BCS transition. In degenerate quasi-2D Fermi gases, most important are collisions at energies close to the Fermi energy which is now proportional to the (2D) density of the gas. Then, due to the logarithmic dependence of the interparticle interaction on the particle energies, the exponential dependence of the critical temperature on the interaction strength transforms to a power law dependence of this temperature on the density. This a striking difference from the 3D case. In a two-component Fermi gas, the s-wave pairing is possible between atoms in different internal states. We propose to reach the BCS transition by adiabatic decrease of the 2D density or by variations of the potential of the tight confinement.

 

New Approaches to Confined Atom Interferometers

Dave Pritchard

Center for Ultracold Atoms at MIT and Harvard

Interferometers in which the atoms are held localized in a trap or waveguide (rather than allowed to propagate in free space) offer numerous scientific opportunities and technical advantages. However, progress on the most popular track - atom chips with microfabricated wires that generate magnetic waveguides - has been hampered by several significant obstacles. I will describe several alternative approaches that we are pursuing, with preliminary results.

 Bose-Einstein Condensates on an Atom Chip

Halina Rubinsztein-Dunlop

Centre for Biophotonics and Laser Science, School of Physical Sciences, University of Queensland, St. Lucia, QLD. 4072, Australia
Phone: +61-7-3365 3139, email: halina@physics.uq.edu.au

Ultra-cold neutral atoms and Bose-Einstein condensates (BECs) are providing some fascinating insights into the fundamental nature of matter. A recent development, the "Atom Chip", provides a reliable and versatile way to produce and manipulate condensates and also offers the possibility of realising new, chip-based quantum devices. The quest for realising coherent waveguides, beamsplitters and interferometers for matter is driving progress in this field at an astounding rate.

We have recently produced BECs on a new type of atom chip based on silver foil. We fabricate atom chip with thick wires capable of carrying currents of several amperes without overheating. The silver surface is highly reflective to light resonant with optical transitions used for Rb. The pattern on the chip consists of two parallel Z-trap wires, capable of producing two-wire guide, and two additional endcap wires for varying the axial confinement.

We describe our experimental procedure for producing condensates in magnetic microtraps formed within 1 mm of surface of the chip. Recent experiments have observed that cold atom clouds fragment into lumps when brought close to the chip surface. This results from a perturbed trapping potential caused by nanometer deviations of the current path through the wires on the chip. We have also seen fragmentation of cold clouds at distances below 100 mm from the wires and are investigating the origin of the deviating current. We also investigate the dynamics of atoms in these microtraps.

 Towards Ultracold Fermions on a Chip

S. Aubin, M. Extavour, S. Myrskog, A. Stummer, and J. H. Thywissen

Department of Physics
University of Toronto, Canada

In a new lab in Toronto, we have been working towards loading quantum degenerate Potassium 40 onto an atom chip. Since microfabricated magnetic traps can have high aspect ratios, such a system will enable the study of quasi-one-dimensional Fermi gases, as well as load optical traps for either one- or two-dimensional confinement. We will present our motivation for choosing this technical approach, the latest experimental progress, and some ideas for future experiments.

 

Experiments with Dense 2D Atomic Hydrogen Gas on Liquid Helium Surfaces


S. Vasilyev, J. JÄarvinen, and S. Jaakkola


University of Turku
Turku, Finland
 

Abstract PDF

 Observation of a 1D Tonks-Girardeau Gas

David S. Weiss

Penn State University
104 Davey Lab
University Park, PA 16802

I will describe our experiments on 1D Bose gases. We use a combination of conservative light traps to prepare and study atoms in 1D at nearly zero temperature. We can scan across coupling regimes and we have access to several observables with which to test the exact 1D Bose gas theory [1,2] . In particular, I will discuss our observation of a Tonks-Girardeau gas[3].

[1] E.H. Lieb and W. Liniger, Phys. Rev. 130, 1605 (1963).
[2] M. Olshanii and V. Dunjko, Phys. Rev. Lett. 91, 090401 (2003).
[3] T. Kinoshita, T. Wenger, and D. S. Weiss, Science 305, 1125 (2004).

 Effect of Feshbach Resonances on Collisions in Atomic Waveguides

Vladimir Yurovsky

Tel Aviv University
Ramat Aviv
Tel Aviv, 69978 Israel

A problem of collisions of atoms with two-channel zero-range interaction under cylindrical harmonic confinement is solved by using of a renormalization procedure. A matching of the solution to a solution of the related one-dimensional problem leads to relation between the one-dimensional and three-dimensional scattering parameters.

At low collision energies the confined scattering amplitude can be approximated by the one-dimensional one. At higher energies the opening of transverse channels leads to resonances in the confined scattering amplitude. Its average behavior can be approximated by the amplitude of three-dimensional free collisions.

The confined two-body system has two or one bound states below or above the resonance, respectively. Shallow bound states are similar to ones of the related one-dimensional system, while deep ones are similar to bound states of two free atoms. A Feshbach resonance also affects a one-dimensional three-body scattering.

 

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ACCOMMODATIONS

Listed below are the names and, where possible, the 800 numbers of hotels and a bed and breakfast agent to assist you in getting accommodations for the upcoming Workshop.

It is especially important that you book a room for the workshop right away as the fall is a very busy time in Cambridge, and you might not be able to get one of the cheaper bed and breakfasts. As housing is expensive in Cambridge/Boston, you may wish to get together with a friend and share a room.

The hotels are within walking distance of the Institute, the Sheraton a short walk and the other two longish walks. They all are on bus routes:

Best Western Homestead Inn, 220 Alewife Brook Parkway, Cambridge,
MA 02138; (617) 491-1890 or 1 (800) 528-1234

Harvard Manor House, 110 Mt. Auburn St., Cambridge, MA 02138
(617) 864-5200

Sheraton-Commander, 16 Garden St., Cambridge, MA 02138; (617) 547-4800 or 1 (800) 325-3434

Boston Reservations/Boston Bed & Breakfast, Inc., 1643 Beacon St., Suite
23, Waban, MA 02168; (617) 332-4199; Fax: (617) 332-5751; e-mail: bostonreservations@bostonreservations.com

All of this information plus more is on the ITAMP web page at http://www.cfa.harvard.edu/itamp under "living accommodations."

We recommend your booking through Boston Reservations/Boston Bed & Breakfast, as in most cases they can get you a room at lower cost than a cold call will get you. If you tell them you are attending a workshop at the Harvard Observatory, they will make every effort to book you at a bed and breakfast, or hotel if you wish, in close proximity. They have many comfortable accommodations in the surrounding neighborhood, and previous workshop participants have been very satisfied with their rooms.

We also strongly advise your not bringing or renting a car. There is no visitor parking at the Observatory and most on-street parking in Cambridge is designated for Cambridge residents only. There are few places in Cambridge and Boston that aren't easily accessible by public transportation and we recommend it highly.

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