Calendar of Physics Talks Vienna

Coherent optoelectronics with quantum dots
Speaker:Artur Zrenner (Universität Paderborn und Center for Optoelectronics and Photonics Paderborn (CeOPP))
Abstract:In optical experiments on single self-assembled InGaAs quantum dots the exciton ground state transition appears as a two-level system with a lifetime limited line width of a few µeV [1]. For the case of pulsed laser fields and in the absence of decoherence, the ground state exciton represents a qubit. Excitations with ps laser pulses result in qubit rotations. Using state projection by tunnelling and photocurrent detection, the state readout can be performed in quantitative way [2, 3]. As a function of electric field induced detuning Ramsey fringes of a single exciton qubit can be observed and controlled for double pulse excitation [4, 5]. In such experiments it is possible to demonstrate voltage controlled qubit manipulations within a wide range of pulse delays. Using fast electric signals, which are phase-locked to ps-laser pulses, the coherent control of an exciton qubit can be obtained by electric switching [6]. Such voltage controlled qubit manipulations seem to be essential for new types of optoelectronic quantum gates and novel applications in the field of coherent optoelectronics. Literature: [1] S. Stufler, P. Ester, A. Zrenner, and M. Bichler, Appl. Phys. Lett. 85, 4202 (2004). [2] A. Zrenner, E. Beham, S. Stufler, F. Findeis, M. Bichler, and G.Abstreiter, Nature 418, 612 (2002). [3] S. Stufler, P. Ester, A. Zrenner, and M. Bichler, Phys. Rev. B 72, 121301 (2005). [4] S. Michaelis de Vasconcellos, S. Stufler, S.-A. Wegner, P. Ester, A. Zrenner, and M. Bichler, Phys. Rev. B 74, 081304(R) (2006). [5] S. Stufler, P. Ester, A. Zrenner, and M. Bichler, Phys. Rev. Lett. 96, 037402 (2006). [6] S. Michaelis de Vasconcellos, S. Gordon, M. Bichler, T. Meier and A. Zrenner, Nature Photonics 4, 548 (2010).
Date: Mon, 04.10.2010
Time: 17:30
Duration: 60 min
Location:TU Wien / Institute of Photonics, Seminarraum 387 Gusshausstraße 27 – 29, Neues EI, Stiege II, Erdgeschoß, 1040 Wien
Contact:Prof. Karl Unterrainer / Thomas Moldaschl

Instabilities in the Quark-Gluon Plasma
Speaker:Maximilian Attems (TU Wien)
Abstract:The quark-gluon plasma (QGP) is a phase at extremely high temperatures formed by deconfined quarks and gluons as predicted by quantum chromodynamics (QCD). Non-Abelian plasma instabilities play a crucial role in the nonequilibrium dynamics of a weakly coupled QGP. The evolution of Chromo-Weibel instabilties can be carried out thanks to real-time lattice simulations. The developed hard-expanding-loop (HEL) formalism allows the (numerical) calculation of the time evolution of gluonic mean fields in full 3 dimensional Bjorken expansion.
Date: Tue, 05.10.2010
Time: 12:30
Duration: 60 min
Location:Uni Wien (Boltzmanngasse 5, 5th floor, Schrödinger HS / large seminar room)
Contact:Niklas Johansson