Berlin 2012 – scientific programme

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PV: Plenarvorträge

PV 13: PV XIII

PV 13.1: Prize Talk

Wednesday, March 28, 2012, 13:15–14:00, H 0105

Optical approach to spin qubits — •Alex Greilich — Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Deutschland — Laureate of the Walter-Schottky-Prize

Spins of carriers confined in semiconductor quantum dots (QDs) are represented as a prototype quantum bit (qubit) for quantum information. Its solid state implementation has the potential for scalability and the possibility being incorporated both into electronic and photonic circuits with existing semiconductor technology.

Giant optical dipole moment and direct optical band gap of a semiconductor QD suggests exploiting the elementary optical excitations as an auxiliary state for ultrafast conversion between optical coherence and spin coherence. It allows the quantum operations to be performed at a terahertz rate or faster. This time is usually compared with spin coherence time. Due to confinement the spin is largely protected from relaxation mechanisms, leading to coherence times in the µs-range. The opportunity to combine long coherence and fast optical control has stimulated considerable progress for spin qubit realization with QDs.

This work demonstrates the development of the key components for such a qubit. It includes: 1. Definition of qubit based on electron and hole spin, 2. Optical spin initialization, 3. Measurement of spin coherence, 4. Ultra-fast coherent spin manipulations, and 5. Control of two-spin entanglement.