Berlin 2005 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 63: Ultrakurzzeitph
änomene
HL 63.10: Vortrag
Mittwoch, 9. März 2005, 13:00–13:15, TU P-N201
Coupling two quantum dots: Förster or direct dipole interaction? — •Christoph Lienau1, Thomas Unold1, Kerstin Müller1, Thomas Elsaesser1, and Andreas D. Wieck2 — 1Max-Born-Institut für Nichtlineare Optik undKurzzeitspektroskopie, 12489 Berlin — 2Ruhr-Universität Bochum, 44870 Bochum
A variety of theoretical ideas for quantum dot (QD) based implementations of quantum logic have been discussed over the last years. Most of these schemes rely on short-range dipole-dipole couplings between neighboring QDs. On the experimental side, however, fairly little is known about such interactions, as they are often difficult to probe in ensemble studies.
Here, we report a combined experimental and theoretical study of dipolar interactions between two individual quantum dots. Ultrafast laser pulses are used to coherently control exciton states in a single quantum dot [1] and perform single-exciton Rabi rotations. Manipulation of this QD strongly modifies the energy spectrum of an adjacent QD - Rabi oscillations are also observed in the nonlinear response of the second QD. The theoretical analysis indicates that unlike in atomic systems the coupling between the quantum dots arises mainly from permanent excitonic dipole moments, whereas quasi-resonant (Förster) energy transfer is weak. Since such a coupling is readily controllable by means of external electric fields, new possibilities for realizing QD-based quantum logic with ultrafast laser pulses emerge.
[1] T. Guenther et al., Phys. Rev. Lett. 89 057401 (2002), 92 157401 (2004).