Regensburg 2007 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 44: Semiconductor Microcavities and Entangled States in Quantum Dots
HL 44.4: Hauptvortrag
Donnerstag, 29. März 2007, 15:30–16:00, H15
Exciton qubits: From Rabi oscillations towards optoelectronic quantum gates — •Artur Zrenner1, Stefan Stufler1, Patrik Ester1, Steffen Michaelis de Vasconcellos1, Marc C. Hübner1, Max Bichler2, Pawel Machnikowski3, Vollrath M. Axt4, and Tilmann Kuhn4 — 1Universität Paderborn, Warburger Straße 100, D-33098 Paderborn, Germany — 2Walter Schottky Institut, Technische Universität München, Am Coulombwall, D-85748 Garching, Germany — 3Instytut Fizyki Politechniki Wrocławskiej, Wybrzeze Wyspiańskiego 27, PL-50-370 Wrocław, Poland — 4Institut für Festkörpertheorie, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Straße 10, D-48149 Münster, Germany
In optical experiments on single self-assembled InGaAs quantum dots we detect the exciton ground state transition as an extremely narrow resonance. 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 multiple qubit rotations, which are demonstrated in a quantitative way as Rabi oscillations in photocurrent experiments. By resonant two-photon excitation we are further able to create and control coherent biexciton states. Under the condition of slight electric field induced detuning we observe Ramsey fringes of a single exciton qubit. In those experiments we are able to demonstrate fringes with a spectral half period below the homogeneous linewidth of the quantum dot. With our results we demonstrate voltage controlled qubit manipulations, which are essential for new types of optoelectronic quantum gates and precision quantum measurements.