Harald Schadwinkel

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Harald Schadwinkel

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Dr. Harald Schadwinkel

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PhD student

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Publications(up to 2000)

H. Schadwinkel, V. Gomer, U. Reiter, B. Ueberholz and D. Meschede
Quantum Fluctuations of a Single Trapped Atom: Transient Rabi Oscillations and Magnetic Bistability, IEEE J. of Quantum Electronics 36, 1358 (2000)arXiv BibTeX
ABSTRACT »
Isolation of a single atomic particle and monitoring its resonance fluorescence is a powerful tool for studies of quantum effects in radiation-matter interactions. We present observations of quantum dynamics of an isolated neutral atom stored in a magneto-optical trap. By means of photon orrelations in the atom's resonance fluorescence we demonstrate the well-known phenomenon of photon antibunching which corresponds to transient Rabi oscillations in the atom. Through polarization-sensitive photon correlations, we show a novel example of resolved quantum fluctuations: pontaneous magnetic orientation of an atom. These effects can only be observed with a single atom.

H. Schadwinkel, U. Reiter, V. Gomer and D. Meschede
Magneto-optical trap as an optical lattice, Phys. Rev. A 61, 013409 (1999)BibTeX
ABSTRACT »
We study the magneto-optical trap (MOT) as an optical lattice with a setup providing full phase control for all light fields. Although completely different light fields are possible for various phases, we have found experimental evidence that stored atoms are generally localized in micropotentials of the six-beam lattice. The influence of the phase variation is surprisingly small, suggesting that the robust behavior of the MOT is a consequence of this fact. We find furthermore good agreement of our experimental data with a simple theoretical model which reduces the complicated MOT to a description of steady-state atoms localized at points of the deepest adiabatic light-shift potential.

H. Schadwinkel
Die Magnetooptische Falle als lichtgebundenes Atomgitter, (1998), PhD thesisBibTeX
ABSTRACT »
Im Rahmen dieser Arbeit wird die Dynamik von lasergekühlten Cäsiumatomen in dreidimensionalen lichtinduzierten Potentialen untersucht. Die Charakterisierung von Lichtfeldern zeigt, daß im Allgemeinen sowohl deren Polarisation als auch Intensität räumlich variieren. Das Interfernzmuster hängt dabei entscheidend von den relativen Phasen zwischen den beteiligten Laserstrahlen ab. Für die experimentelle Kontrolle wurde ein neuartiges Konzept entwickelt, das die intrinsische Stabilität der relativen Zeitphasen eines Lichtfeldes gewährleistet. Mit diesem Aufbau wurden erstmals zwei spezielle Konfigurationen studiert, die als reine Polarisationsgitter (NOT) bzw. Intensitätsgitter (MOT₀₀) interessante Grenzfälle darstellen.

A. Rauschenbeutel, H. Schadwinkel, V. Gomer and D. Meschede
Standing light fields for cold atoms with intrinsically stable and variable time phases, Opt. Comm. 148, 45 (1998)BibTeX
ABSTRACT »
We present a novel method to realise a standing light field with a stable configuration in two or three dimensions. A single standing wave formed by two counterpropagating beams is folded and brought into intersection with itself. The values of the relative timephases are stable, a priori known, and can be altered arbitrarily by means of retardation plates. The polarisation configurations of three orthogonal standing waves include the standard magnetooptical trap and a novel three-dimensional pure polarisation lattice which we have investigated in a first spectroscopic measurement, providing strong evidence for atomic localisation in both cases.

F. Strauch, V. Gomer, H. Schadwinkel, B. Ueberholz, D. Haubrich and D. Meschede
Diffraction by cold atoms, Opt. Comm. 145, 57 (1997)BibTeX
ABSTRACT »
We have observed diffraction of a laser probe beam by a trapped sample of cold atoms. The effect is only visible in the vicinity of a resonance line. The observed diffraction pattern arises from interference of the incident and scattered light wave, allowing reconstruction of geometric properties of the trapped sample from the holographic record.

V. Gomer, O. Harms, D. Haubrich, H. Schadwinkel, F. Strauch, B. Ueberholz, S. aus der Wiesche and D. Meschede
Magnetostatic traps for charged and neutral particles, Hyperfine Interactions 109, 281-292 (1997)BibTeX
ABSTRACT »
We have constructed magnetostatic traps from permanent magnets for trapping charged and neutral atoms. Two storage experiments are presented: a compact Penning trap for light ions and magnetic trapping of single neutral atoms. The dynamics of cold neutral atoms and their loss mechanisms in a quadrupole magnetostatic trap are discussed.

D. Haubrich, H. Schadwinkel, F. Strauch, B. Ueberholz, R. Wynands and D. Meschede
Observation of individual neutral atoms in magnetic and magneto-optical traps, Europhys. Lett. 34, 663 (1996)BibTeX
ABSTRACT »
We have identified and photographed individual cesium atoms in a magneto-optical trap with steep magnetic gradients. By switching off the trapping light fields, single atoms were released to a bound state of the magnetic potential. A storage time of 38 s was measured for purely magnetic trapping, whereas a storage time of 147 s was observed in the corresponding magneto-optical trap.

A. Höpe, D. Haubrich, H. Schadwinkel, F. Strauch and D. Meschede
Optical Trapping in a Cesium Cell with Linearly Polarized Light and at Zero Magnetic Field, Europhys. Lett. 28, 7 (1994)BibTeX
ABSTRACT »
We have found that linearly polarized light can be used efficiently for optical trapping of cesium atoms in a magnetic-quadrupole field. The number and density of atoms of the trapped samples are comparable to a standard magneto-optical trap with σ⁺ - σ^– polarized light, but the influence of the magnetic-quadrupole strength is strikingly different. When the polarization of counterpropagating light beams is orthogonal, trapping is observed also for zero magnetic field.