Seminar 28.11.13, 2:00 pm st, Room D326
Dr. Alessandro Zenesini
Institute of Quantum Optics
Leibniz Universität Hannover
"The problem of three interacting particles. A brief experimental and theoretical history"
In classical physics the problem of three interacting particles has always been an hard task and the precise dynamics of the system can be solved only under special conditions. This happens, for example, when one mass is much larger than the other two, the sun-earth-moon system.
Triggered by the unsolved problem on three interacting nucleons, Vitaly Efimov, found an elegant solution to the quantum mechanic problem, a beautiful example of how symmetries simplify the analytical approach.
Unfortunately no experimental evidences of the Efimov results have been found before the ultracold atoms era.
In this talk I will give a brief history of the theoretical solution and of the 35 years long search for experimental evidences.
Seminar 05.12.13, 2:00 pm st, Room D326
Physikalisch Technische Bundesanstalt Braunschweig
Towards optical Feshbach resonances with 40Ca
Alkaline earth metals find applications in various fields of research and technology. Especially due to the narrow singlet- triplet intercombination line, photoassociation (PA) and optical Feshbach resonance (OFR) experiments have been the subject of research in the last decade. Compared to the other alkaline earth like metals strontium and ytterbium, where PA and OFR have already been performed, calcium offers an even narrower intercombination line of G ≈ 2p 374 Hz, which is supposed to solve loss problems at OFR resonances. We recently produced a quantum degenerate 40Ca gas using a two stage magneto-optical trap and subsequent forced evaporation cooling in an optical dipole trap. The interaction in the gas depends on the scattering length, which we plan to tune using the OFR. As a first step in the two molecular potentials c (Ω = 0) and a (Ω = 1) correlating to the 3P + 1S asymptote the six weakest bound photoassociation resonances were measured. Based on this data set these molecular potentials were fitted using a coupled channel model. On the basis of the experimentally observed spectra we can predict the practicability of OFR resonances and their corresponding losses, which are in good agreement with the coupled channel model. The results indicate calcium as a perfect candidate for low loss modification of the scattering length by OFR.
Seminar 16.01.14, 2:00 pm st, Room D326
Dr. Hendrik Weimer
Institut für Theoretische Physik
Leibniz Universität Hannover
Dissipative quantum state preparation
While dissipation is generally thought to be an undesirable process for the observation of coherent dynamics, it is actually possible to turn controlled dissipation into a useful resource for the realization of tailored quantum states. In this context, I will discuss the prospects for the dissipative preparation of strongly correlated few- and many-body states. I will also present possible experimental realizations based on Rydberg atoms or ultracold polar molecules.