Optically Driven Qubits in Artificial Molecules

We present novel models of quantum gates based on coupled quantum dots in which a qubit is regarded as the superposition of ground states in each dot. Coherent control on the qubit is performed by both a frequency and a polarization of a monochromatic light pulse illuminated on the quantum dots. We also show that a simple combination of two single qubit gates functions as a controlled NOT gate resulting from an electron-electron interaction. To examine the decoherence of quantum states, we discuss electronic relaxation contributed mainly by LA phonon processes. Typeset using REVTEX ∗Electronic address; [email protected] †Also with Department of Electrical Engineering, University of Seoul, Seoul 130-743, Korea ‡Electronic address; [email protected] §Permanent address: Department of Electronics Engineering, Korea University, 5-1 Anam, Sungbook-ku, Seoul 136-701, Korea 1