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Physical Society Colloquium
Carlo Piermarocchi University of California San Diego Semiconductor quantum dots are artificial nanostructures with electronic and optical properties very similar to those of an atom. Like atoms, optical control can be used to manipulate the quantum states but, unlike an atom, the dot is easy to locate and to integrate in a semiconductor device. The coherent control of excitons (photo-excited electron hole pairs) and bi-excitons by Rabi rotations in a single quantum dot have been experimentally realized. I will show how these basic manipulations can be organized to run basic two-qubit quantum algorithms. I will illustrate analytical and numerical methods to design shaped optical pulses and realize a given quantum transformation in the shortest time as possible. This will keep the operation of this prototype semiconductor quantum computer within its decoherence time. Each dot can be prepared with an excess conduction electron. In this case, coherent optical techniques can be used to control the spin state of the single electron. I will show how an effective exchange coupling between electrons on two neighboring dots can be induced and controlled optically. This coupling leads to quantum manipulations robust against decoherence by spontaneous emission. Applications to the control of spin entanglement and to the realization of quantum gates in an array of dots are discussed.
Friday, January 25th 2002, 15:30 |