An optically driven quantum dot quantum computer

We propose a design for a quantum computer that builds on n-type SET structures reported by Tarucha et al. (1996). Our design consists of an array of free standing pillars with source and drain electrodes at the top and bottom of the pillar and a stacked series of asymmetric GaAs/AlGaAs quantum wells arrayed along the axis. By applying a negative bias to the cylindrical gate electrode, carriers near the surface are depleted. The parabolic electrostatic potential provides confinement in the radial direction while bandgap discontinuities in the quantum wells provide confinement along the pillar axis. In operating as a quantum computer the source and drain are grounded and the number of electrons in each dot are set to one by adjusting the gate voltage. Qubits are encoded in the ground state and first excited state of the quantum dot electrons. The pillar array constitutes an ensemble of quantum computers that operate simultaneously.