Optically driven qubits in artificial molecules - art. no. 052306

We present models of quantum gates based on coupled quantum dots in which a qubit is regarded as the superposition of ground states in each dot. Coher ent control on the qubit is performed by a monochromatic light pulse illumi nated on the quantum dots. Considering particular types of artificial molec ules, we show that the qubit is easily manipulated with the polarization an d frequency of a light pulse and, especially, the controlled-Nor operation can be possible exploiting the electron-electron interaction. To examine th e decoherence of quantum states, we discuss electronic relaxation contribut ed mainly by LA phonon processes.