Calendar of Physics Talks Vienna

Integrated quantum optics and information processing
Speaker:Christine Silberhorn (Universität Paderborn)
Abstract:Photonic quantum systems have become an established standard for quantum communi¬cation and information processing applications. Linear optical networks, which comprise multiple optical modes as well as highly non-classical states of light, have been investigated intensively over the last decades in various theoretical pro¬posals. Still, the implementation of more advanced setups with increased complexity in terms of number of channels or quantum input states, remains challenging. These can serve as an ideal test-bed for different applications in quantum optics and quan¬tum information science. Integrated optic devices – such as optical fibers, waveguides or linear optical circuits – in combination with pulsed quantum light and time-multiplexing configurations offer distinct advantages to realize quantum optical experiments. The experimental setups get ..
Date: Mon, 14.05.2012
Time: 17:30
Duration: 60 min
Location:TU Wien, Schütte-Lihotzky Hörsaal, HS 7, Karlsplatz 13, 1040 Wien
Contact:Dr. Christiane Losert / Univ. of Vienna

Chiral and deconfinement transitions in QCD-based theories with chemical potential in a small volume
Speaker:Joyce Myers (University of Groningen)
Abstract:The phase diagram of QCD at non-zero chemical potential is difficult to calculate because the coupling strength is large, preventing ordinary perturbation theory, and the action is complex, leading to the "sign problem" and preventing conventional lattice simulations. To understand better how to deal with complex actions and to obtain a qualitative picture of the phase diagram of QCD it can be useful to study the theory in a very small spatial volume, which allows for perturbation theory to be employed at all temperatures. We consider QCD and QCD-based theories on S^1 x S^3 for small S^3 from one-loop perturbation theory. The quark number, free energy, and Polyakov lines as a function of the temperature and chemical potential provide a sketch of the phase diagram for QCD and supersymmetric QCD in the limit of large Nc and Nf.
Date: Tue, 15.05.2012
Time: 12:30
Duration: 60 min
Location:Vienna University of Technology: Wiedner Hauptstr. 8-10, 10th floor (yellow), seminar room E136
Contact:Vienna Theory Lunch Seminar (http://www.univie.ac.at/lunch-seminar/)

Störungstheoretische AQFT: das Epstein-Glaser Verfahren
Speaker:Andreas Merckel und Albert Passegger (Univ.Wien)
Abstract:im Rahmen des Seminars für Mathematische Physik
Date: Tue, 15.05.2012
Time: 14:15
Location:Fakultät für Physik, Erwin Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock
Contact:J. Yngvason

Multi-photon Absorption: measurement of Cross sections and selected Applications
Speaker:MSc. Aliasghar Ajami (Technische Universität Wien, Institut für Angewandte Physik)
Abstract:Multi-photon absorption is a nonlinear process in which two or more photons are nearly simultaneously absorbed to excite a molecule from ground state to an excited state via virtual states. Many techniques have been proposed to determine the multi-photon absorption cross section within them the Z-scan method is the most sensitive and also easiest to perform. The Z-scan technique is a single beam method in which the nonlinear sample is scanned along the propagation direction of a tightly focused laser beam while the transmitted energy through the sample is measured as a function of the sample position. We extended existing theories in order to eliminate limitation for evaluating the two-photon absorption (TPA) of samples in general. In particular, the cross section of various Two-photon initiators (TPI) has been determined. The special design of these compounds is aimed at increase of their TPA cross section in order to be utilized in two-photon induced polymerization (TPIP). TPIP is a potential application of TPA by which a real 3D structure can be created. In this process an ultrashort pulsed laser beam is tightly focused within a resin mixed with a TPI using a high numerical aperture objective. Due to the intensity dependence nature of nonlinear absorption, only in a small volume around the focal point the nonlinear absorption could happens. A TPI molecule is dissociated after absorbing light and produce free radicals which trigger the polymerization process. Scanning the focal point of the laser beam within the resin in three dimensions allows one to create a real 3D micro-structure. Several illustrative examples of 3D microstructures fabricated in our lab will be presented to demonstrate the interesting aspects of the method.
Date: Tue, 15.05.2012
Time: 16:00
Location:Technische Universität Wien, Institut für Angewandte Physik, Seminarraum 134A, Turm B (gelbe Leitfarbe), 5. OG, 1040 Wien, Wiedner Hauptstraße 8-10
Contact:Ao.Univ.Prof. Dr. Wolfgang Husinsky