|
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 |
|