Bose-Einstein condensates in free fall

Oliver Gabel

Observing freely falling objects has been the cornerstone of Isaac Newton's mechanics and has also led to the modern understanding of space-time as formulated by Albert Einstein. Recently, the QUANTUS collaboration (QUANTen Gase Unter Schwerelosigkeit) has realised a free-fall experiment with Bose-Einstein condensates (BECs) from a height of 110 m.

For such long expansion times in free fall of 1 s, the approximation of non-relativistic quantum mechanics becomes a less accurate description. Thus it becomes relevant to employ general relativity and quantum field theory in curved space-time to model the evolution of BECs and to quantify the relativistic corrections. The goal of this PhD project is to extend the dynamical evolution of BECs to General Relativity and to model and quantify the arising corrections.

 

Theory of atomic scattering of metastable neon atoms (Ne*)

Radial effective box potential with angular momentum l=3 (black). Wave functions of the radial Schrödinger equation for a bound molecular state (green) with negative energy E < 0, a scattering state (red) with positive energy E > 0 and a quasi bound state (blue), also with positive energy.

Christian Cop

Bose-Einstein-Condensation of dilute alkali gases has dominated the past decade of AMO research. With the condensation of noble gases (He*) a new phase has started. Currently, many experiments are geared towards the condensation of other noble gases, rare-earth gases and composite molecules. In the research group of G. Birkl (Opens external link in new windowhttp://www.iap.tu-darmstadt.de/apqneu/) significant effort is spent on the investigation of the possibility to condense metastable neon (Ne*).

In the present research project we will examine the binary scattering physics of metastable neon atoms. Starting from simple and analytically solvable model potentials we investigate the basic principles of multichannel scattering theory. This is generalized to realistic extended potentials in order to evaluate the scattering matrix and inelastic loss rates. Eventually, we will address the loss rates due to a fragmentation process (penning ionization) which could be obstacle towards Bose-Einstein-Condensation.

Coherence studies of quantum dot superluminescent diodes

Quantum dot superluminescent diode: device (courtesy of AG Elsäßer) (top) and model (bottom)

Franziska Friedrich

During the last years, spectrally broadband emitting superluminescent diodes (SLDs) became essential elements in modern research due to their high potential in industrial applications, e.g. in optical coherence tomography or fiber sensor technology. Here, light generation arises at the transition of spontaneous to stimulated emission, the range of amplified spontaneous emission (ASE). The delicate choice of waveguide geometry and gain medium, here quantum dots (QDs), enables large spectral widths of some THz as well as spatial coherence.

From a theoretical point of view, Opens external link in new windowcharacterization of ASE generated by QD-SLDs and investigation of their photon statistical behavior (especially at a particular temperature regime, where a Opens external link in new windowreduction of the intensity correlation down to 1.33 is observable), represents an interesting and challenging project of research, which we analyze on a microscopic level.

 

Kontakt

Prof. Dr. Reinhold Walser

Theoretische Quantendynamik
Institut für Angewandte Physik
Fachbereich 05 - Physik
Technische Universität Darmstadt
Hochschulstr. 4a
D-64289 Darmstadt

+49 6151 16-20320

+49 6151 16-20402

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