# Dresden 2006 – wissenschaftliches Programm

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# HL: Halbleiterphysik

## HL 52: Quantum dots and wires: Optical properties IV

### HL 52.5: Vortrag

### Freitag, 31. März 2006, 12:00–12:15, POT 151

**Tailored quantum dots for entangled photon pair creation** — •Thorsten Berstermann^{1}, Alex Greilich^{1}, Matthias Schwaab^{1}, Thomas Auer^{1}, Ruth Oulton^{1}, Dimitri Yakovlev^{1}, Manfred Bayer^{1}, Victorina Stavarache^{2}, Dirk Reuter^{2}, and Andreas Wieck^{2} — ^{1}Experimentelle Physik 2, Universität Dortmund, D-44221 Dortmund, Germany — ^{2}Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum, Germany

Entangled photon pairs from quantum dots (QD) are the key requirement for quantum-cryptography and quantum teleportation [1]. Lowering the symmetry of a QD leads to an asymmetry-induced exchange splitting δ between the two bright exciton energy levels. In order to obtain polarization entangled photon pairs from the biexciton radiative decay cascade, this splitting should be smaller than the homogeneous linewidth γ of each level. In this talk we compare the asymmetry-induced exchange splitting δ of the bright-exciton ground-state doublet in self-assembled (In,Ga)As/GaAs quantum dots, determined by Faraday rotation with its homogeneous linewidth γ, obtained from the radiative decay in time-resolved photoluminescence and differential transmission. Post-growth thermal annealing of the dot structures leads to a considerable increase of the homogeneous linewidth, while a strong reduction of the exchange splitting is simultaneously observed. The annealing can be tailored such that the asymmetry-induced exchange splitting becomes even smaller than the homogeneous linewidth.

[1]D.Bouwmeester, A.Ekert, A.Zeilinger, The Physics of Quantum Information, Springer, Berlin(2000)