aktualisiertes pdf - DPG-Tagungen

tion to Rydberg states (n = 40...∞) with two narrow-bandwidth diode
laser systems. The excited atoms are detected by field ionization.
We present our technological approach and first measurements aimed at
the observation of the ”dipole blockade”[2]. This interaction effect is a
preliminary step towards quantum computation with Rydberg atoms.
The perspectives of the experiment for many-body physics will be discussed.
[1] P. Treutlein et al., Phys. Rev. A. 63, 051401R (2001).
[2] M. D. Lukin et al., Phys. Rev. Lett. 87, 037901 (2001).
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Atomic beam splitters using multistate adiabatic passage
— •Monika Pietrzyk 1 , Razmik Unanyan 1 , Michael Fleischhauer
1 , Klaas Bergmann 1 , and Bruce Shore 2 — 1 Fachbereich
Physik, Technische Universiteat Kaiserslautern — 2 618 Escondido
Circle, Livermore CA
We describe a technique for creating a superposition of degenerate
quantum states of atoms or molecules by manipulating the polarization
of three pulsed laser beams. We consider an atomic beam splitter using
levels of the metastable neon Ne* atoms with J=2 and J=1. The proposed
technique is a generalization of the simulated Raman adiabatic
passage (STIRAP) technique, and thus is insensitive to decoherence due
to spontaneous emission. It is also robust with respect to small variations
of the intensity and timing of the laser fields. The implementation of a
Hadamard gate based on the proposed method will be discussed.
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Electronic Structure of Atoms in Magnetic Quadrupole Traps
— •Igor Lesanovsky 1 , Jörg Schmiedmayer 1 und Peter Schmelcher
1,2 — 1 Universität Heidelberg- Physikalisches Institut, Philosophenweg
12, 69120 Heidelberg — 2 Universität Heidelberg-Physikalisch Chemisches
Institut, INF 229, 69120 Heidelberg
For the manipulation of ultra-cold atoms magnetic fields play an essential
role. As long as the spatial variation of the magnetic field are much
less than the typical atomic length scale an atom behaves like a neutral
particle coupling to the external field by its total spin only. For Rydberg
atoms this does not hold and the coupling of the charge of the atomic
constituents has to be taken into account. We investigate the electronic
structure of atoms exposed to a magnetic quadrupole field. Here, in contrast
to the homogeneous field, the spin and spatial degrees of freedom
are coupled leading to unique properties of the electronic states. An inspection
of the systems symmetries reveals a two-fold degeneracy of the
electronic states in the presence of the field. We analyze both low-lying
and highly excited states over a broad regime of field gradients. The delicate
interplay between the Coulomb and various magnetic interactions
leads to complex patterns of the spatial spin polarization of individual
excited states. We also study electromagnetic transitions and point out
differences to the electromagnetic spectrum observed in a homogeneous
magnetic field. Furthermore we show that the magnetic quadrupole field
induces a permanent state dependent electric dipole moment of the atom.
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Eine Lithium-MOT als Target für Ionisationsexperimente —
•Jochen Steinmann, Martin Dürr, Cornelia Höhr, Alexander
Dorn und Joachim Ullrich — Max-Planck-Institut für Kernphysik,
Saupfercheckweg 1, 69117 Heidelberg
Die Dynamik von Vielteilchenquantensystemen läßt sich in kinematisch
vollständigen Experimenten zur Stoßionisation von Atomen, in denen
die Impulse aller beteiligten Fragmente bestimmt werden, im Detail
untersuchen.
Wesentlich, besonders zur Überprüfung von theoretischen Ansätzen,
sind dabei Daten für möglichst einfache und im Endzustand strukturlose
Targetatome. Für die in der Vergangenheit eingehend untersuchte
Einfach- und die Doppelionisation sind dies Wasserstoff bzw. Helium
[1]. Das Ziel dieser Arbeit ist die Durchführung erster Experimente zur
Doppel- und Dreifachionisation am nächst komplizierten Target Lithium
(mit drei Hüllenelektronen). Dazu wird zur Zeit eine magnetooptische
Falle (MOT) basierend auf einem Diodenlasersystem aufgebaut. Die effiziente
Beladung der Falle erfolgt mit einem Zeeman-Abbremser. Zur
Impulsspektroskopie der Reaktionsfragmente nach Ionisation im Teilchenstoß
(Elektronen, Ionen) oder durch intensive fs-Laserpulse wird die
MOT in ein Reaktionsmikroskop integriert [2].
[1] Dorn et al., Phys. Rev. Lett. 86, 3755 (2001)
27
[2] R. Moshammer et al., Nucl. Inst. Meth. B 108, 425 (1996); H. Kollmus
et al., Nucl. Inst. Meth. B 124, 377 (1997)
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TRIµP - Trapped Radioactive Isotopes as µicrolaboratories for
fundamental Physics — •U. Dammalapati, G.P. Berg, P. Dendooven,
O. Dermois, G. Ebberink, M.N. Harakeh, R. Hoekstra,
L. Huisman, H.H. Kiewiet, R. Morgenstern, J. Mulder,
A. Rogachevskiy, M. Sanchez-Vega, M. Sohani, R.G. Timmermans,
E. Traykov, L. Willmann, H.W. Wilschut, and K. Jungmann
— Kernfysisch Versneller Instituut, Rijksuniversiteit Groningen,
Netherlands
At KVI a new facility is being set up which aims for trapping radioactive
isotopes to study fundamental interactions in physics using
combined atomic and nuclear physics methods. Radioactive nuclides are
created with ion beams from the superconducting cyclotron AGOR in inverse
kinematics and fragmentation reactions. A broad range of possible
products can be separated from the primary beam in a magnetic double
recoil and fragment separator system. The isotopes of interest will be
slowed down in matter and further cooled, confined and bunched using
a segmented radiofrequency quadrupole device. Singly charged species
are guided to experimental stations. After neutralization the atoms will
be optically cooled and stored in atom traps (e.g. MOTs) The research
program pursued by the local KVI group includes precision studies of nuclear
β-decays, through β–neutrino (recoil nucleus) correlations, parity
violation in atoms and searches for permanent electric dipole moments.
Commissioning of the separator facility is foreseen in the course of the
year 2004, where after it will be open for use by outside scientific groups.
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Non-dispersive Wavepackets in Wannier-Stark Systems — •D.
Witthaut, T. Hartmann, S. Mossmann, and H. J. Korsch —
Fachbereich Physik, TU Kaiserslautern
We discuss the dispersion of wavepackets in Wannier-Stark systems,
consisting of a space-periodic potential and possibly time-dependent
fields, both analytically and numerically.
In static 1D systems wavepackets perform a dispersionless periodic motion
(Bloch oscillation), while dispersion generally occurs in driven systems.
Nevertheless one can construct systems that show a dispersionless
motion and even dispersionless transport for certain initial conditions.
In 2D systems the dispersion depends crucially on the direction of
the static field with respect to the lattice, being generally much smaller
than in field-free systems. We analyze the origin of this small systematic
dispersion and its dependence on the field direction.
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Fano’s model in an external periodic perturbation: Exact analytical
solution — •N.B. Sangouard, R.G. Unanyan, L. Plimak,
and M Fleischhauer — Fachbereich Physik, Universität Kaiserslautern,
67653, Kaiserslautern, Germany
Decay of a discrete state into continuum when the amplitude of the
former is inverted periodically is investigated. A decaying ”Floquetresonance”
solution of the Schrödinger equation valid for times large
compared to the inversion period is identified. The decay rate, i.e., the
imaginary part of the quasienergy of the ”Floquet resonance,” can be
controlled by changing the period of the perturbation. Interestingly, the
periodic inversions result in boundedness of the decay rate which stays finite
for an arbitrarily strong coupling between the discrete state and continuum.
This can have interesting applications in quantum computing,
interferometry, and coherent control of reaction optical memory storage,
dynamics.
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Diffusions Quanten Monte Carlo Methode für Atome in starken
Magnetfeldern — •Steffen Bücheler, Jörg Main und Günter
Wunner — Institut für Theoretische Physik, Teilinstitut I, Universität
Stuttgart, Pfaffenwaldring 57/4, 70550 Stuttgart
Die Spektren leichter Atome in starken Magnetfeldern (Neutronensternmagnetfeldern)
sind in der Astrophysik von großer Bedeutung.
Die Lösung der Schrödinger-Gleichung und damit die Berechnung der
Grundzustandsenergie und angeregter Zustände erfolgt durch Anwendung
der Diffusions Quanten Monte Carlo Methode, die mit der Simulation
durch ” Walker“ einhergeht, welche die Dichte der Wellenfunktion
Φ( � R, τ) darstellen. Die Transformation der Schrödinger-Gleichung in