QD molecule
A quantum dot molecule is one possible approach to form a qubit.
An applied electric field can be used to switch between the states, e.g. direct vs. indirect exciton.
Coupled quantum wires
One-dimensional electron transport in combination with wavefunction engineering has been proposed for the use in solid state quantum information processing. An example of such a system is studied in this tutorial: Vertically coupled quantum wires in a longitudinal magnetic field