Scalable solid-state quantum computer based on quantum dot pillar structures

We investigate an optically driven quantum computer based on electric dipole transitions within coupled single-electron quantum dots. Our quantum register consists of a free-standing n-type pillar containing a series of pairwise coupled asymmetric quantum dots, each with a slightly different energy structure, and with grounding leads at the top and bottom of the pillar. Asymmetric quantum wells confine electrons along the pillar axis, and a negatively biased gate wrapped around the center of the pillar allows for electrostatic confinement in the radial direction. We self-consistently solve coupled Schrödinger and Poisson equations and develop a design for a three-qubit quantum register. Our results indicate that a single gate electrode can be used to localize a single electron in each of the quantum dots. Adjacent dots are strongly coupled by electric dipole-dipole interactions arising from the dot asymmetry, thus enabling rapid computation rates. The dots are tailored to minimize dephasing due to spontaneous emission and phonon scattering and to maximize the number of computation cycles. The design is scalable to a large number of qubits.