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[3] D. Schrader et al., Appl. Phys B 73, 819 (2001)
Q 38.9 Do 14:00 Schellingstr. 3
Collective Atomic Motion in an Optical Lattice formed inside a
High Finesse Cavity — •Julian Klinner, Boris Nagorny, Thilo
Elsässer, Malik Lindholdt, and Andreas Hemmerich — Institut
für Laserphysik, Universität Hamburg, Luruper Chaussee 149, 22761
Hamburg
We discuss non-linear light field dynamics and collective atomic motion
in an optical lattice formed inside a high finesse resonator. Our cavity
with a finesse of 180.000 operates in the regime of strong coupling,
where the light shift per photon times the number of trapped atoms
exceeds the cavity bandwidth. We present a theoretical model, which
accurately reproduces our observations of dispersive optical bistability,
self-organisation of the intra-cavity field and self-induced radial breathing
oscillations of the trapped atoms.
Q 38.10 Do 14:00 Schellingstr. 3
Atom Optics and Quantum Information Processing with Atoms
in Optical Micro-Structures — •Andre Lengwenus 1 , Tobias
Müther 1 , Jonas Ries 1 , Falk Scharnberg 1,2 , Niels Ubbelohde 1 ,
Michael Volk 1 , Wolfgang Ertmer 1 , and Gerhard Birkl 1 —
1 Institut für Quantenoptik, Universität Hannover, Welfengarten 1, D-
30167 Hannover, Germany — 2 Swinburne University of Technology, Melbourne,
Australia
A new direction in the field of atom optics, atom interferometry, and
neutral-atom quantum information processing can be based on the use
of micro-fabricated optical elements. With these elements versatile and
integrated atom optical devices can be created in a compact fashion. This
approach opens the possibility to scale, parallelize, and miniaturize atom
optics for investigations in fundamental research and application.
For the implementation of new approaches for quantum information
processing, we use arrays of micro-lenses to create a two-dimensional
system of atom samples in dipole traps that can serve as the carriers
for the qubits. Micro-optical elements are also used to generate
waveguides, beam splitters, and interferometer-type structures for guided
atoms. These systems present the atom-optical equivalents to the respective
structures in integrated light optics.
In the future, the application of micro-optics for the optical manipulation
of atomic systems is expected to have a significant impact on
quantum optics, quantum information processing, and matter wave optics.
We report on the progress of our work.
Q 38.11 Do 14:00 Schellingstr. 3
Transverse confinement effects in stochastic cooling of trapped
atoms. — •Denis Ivanov and Sascha Wallentowitz — Fachbereich
Physik, Universität Rostock, Universitätsplatz 3, 18051 Rostock, Germany.
The operation of stochastic cooling of trapped atoms [1] has been studied
for a 3D isotropic harmonic potential. The change of energy due to a
single cooling step has been obtained in terms of quantum-statistical averages.
Contributions in the motion parallel to the control-laser beam direction
contain the back-action noise due the employed measurement and
noise due to fluctuations of the number of atoms in the control beam [2].
Furthermore, having a control-laser with finite beam-waist, an indirect
measurement of the transverse atomic coordinate with the corresponding
reduction of the quantum state are carried out during the cooling step.
This quantum effect introduces additional noise in the kinetic energy and
depends both on the size and on the shape of the beam-waist [3]. In the
case, where the thermal wavelength of atoms is smaller than the average
interatomic distance, the indistinguishability of atoms can be discarded
and the energy change is expressed in terms of geometrical characteristics
and temperature. Given these results, a boundary between cooling and
heating can be established in dependence on geometrical parameters.
[1] M.G. Raizen et al., Phys. Rev. A 58, 4757 (1998).
[2] D. Ivanov et al., Phys. Rev. A 67, 061401(R) (2003).
[3] D. Ivanov and S. Wallentowitz, J. Opt. B (submitted).
Q 38.12 Do 14:00 Schellingstr. 3
Optical Trapping and Cooling of Fermionic and Bosonic Magnesium
— •Albane Douillet, Tanja E. Mehlstäubler, Nils
Rehbein, Ernst M. Rasel, and Wolfgang Ertmer — Institut für
Quantenoptik, Universität Hannover, Welfengarten 1, 30167 Hannover.
We report on the status of our new experimental apparatus for precision
spectroscopy of ultra cold fermionic and bosonic magnesium atoms.
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Both isotopes are captured from a slowed thermal magnesium beam and
pre-cooled in a magneto-optical trap (MOT). Up to 10 8 atoms can be
trapped with 60 mW light tuned to the transition 3 1 S0 → 3 1 P1 at
285 nm. Time-of-flight measurements indicate atomic temperatures of
about 3 mK, slightly above the Doppler limit (1.9 mK). The experiment
will explore promising avenues towards the µKelvin regime with
magnesium, such as quench cooling, which was recently very successfully
applied for calcium. The need for effective cooling methods was demonstrated
by recent measurements with our Ramsey-Borde interferometer.
The residual atomic motion was one of the major limitations for the
achieved resolutions of about 290 Hz. For the interferometer we are developing
a frequency-doubled Nd:YVO4-disc laser, which provides about
1 W at 914 nm (TEM00).
Q 38.13 Do 14:00 Schellingstr. 3
Tweezing Cold Atoms with Lasers — •Bernd Mohring 1 , Marc
Bienert 1 , Florian Haug 1 , Giovanna Morigi 1 , Mark G. Raizen 2 ,
and Wolfgang P. Schleich 1 — 1 Abteilung für Quantenphysik, Universität
Ulm, 89069 Ulm — 2 Department of Physics, The University of
Texas, Austin, Texas 78712-1081, USA
Quantum tweezers open a promising way to deterministically and coherently
extract a well-defined number of atoms out of a Bose-Einstein
condensate (BEC). We propose a quantum tweezers scheme based on
laser pulses, that allows to coherently transfer atoms from a condensate
into a quantum state of a tight confining dipole trap. The BEC is constituted
by atoms in the hyperfine state |g〉, which is magnetically trapped.
The atoms are transferred into the dipole trap by coupling the state |g〉
to another hyperfine state |e〉, which is confined by the dipole trap. The
coupling is achieved by an adiabatic transfer with laser pulses, of which
two realizations are presented: The adiabatic passage and the “Stark
chirped rapid adiabatic passage” (SCRAP).
Q 38.14 Do 14:00 Schellingstr. 3
Photoionisation von Indium — •Ch. Schwedes, P. Eckle, J. von
Zanthier, A.Yu. Nevsky und H. Walther — MPI f. Quantenoptik,
Hans-Kopfermann-Str. 1, 85748 Garching
Ein einzelnes In + -Ion, gespeichert und lasergekühlt in einer RF-Falle
wird als ein aussichtsreicher Kandidat im Hinblick auf ein optisches Frequenznormal
untersucht [1]. Um eine angestrebte Genauigkeit in der
Spektroskopie von 10 −18 zu erreichen, sind äußerst stabile Bedingungen
der Speicherung notwendig. Die Ionisation von neutralem In durch das
übliche Elektronenstoßverfahren führt jedoch leicht zu zeitlich variierenden
elektrostatischen Aufladungen von Isolatoren in der Fallenregion, die
eine kontinuierliche Spektroskopie erschweren. Dies kann durch Photoionisation
vermieden werden.
Aufgrund der günstigen Niveaustruktur von In, genügt zur effizienten
Zwei-Photonen Ionisation ein einzelner Laser bei 410 nm. Dieser
regt vom Grundzustand zunächst resonant in ein Zwischenniveau an und
von da aus effizient in autoionionisierende diskrete Zustände oberhalb
der Ionisierungsschwelle. Die dabei im Vergleich zur Stoßionisation um
zwei Größenordnungen gesteigerte Ionisierungseffizienz vermindert eine
Bedampfung der Fallenelektroden mit In drastisch, wodurch Kontaktpotentiale,
die zu Heizung des Ions führen können, verringert werden.
Untersuchungen der Effizienz dieses Verfahrens im Vergleich zur Stoßionisation
und zu anderen Photoionisationsverfahren werden vorgestellt.
[1] Becker et al., Phys. Rev. A 63, 051082 (2001).
Q 38.15 Do 14:00 Schellingstr. 3
Laser Spectroscopy and Laser Cooling of Indium — •Bernhard
Klöter, Ruby dela Torre, Jiayu Wang, Dietmar Haubrich,
Ulrich Rasbach, and Dieter Meschede — Institut für Angewandte
Physik der Universität Bonn
Indium is an interesting candidate for Atomic Nanofabrication (ANF)
because it can directly be deposited onto a substrate. The high deposition
rates needed for ANF can only be achieved with a laser cooled thermal
Indium atomic beam, which had not been established before.
We first systematically investigated laser frequency stabilization
schemes for all five frequencies involved in the cooling process.
The poster will present our results on saturation and polarization spectroscopy
of Indium in an all sapphire cell at 410 nm and/or 451 nm, the
laser frequency locking schemes and the different laser cooling methods.