  We design and analyze a solid state qubit based on electron spin and
controlled by electrical means. The coded qubit is composed of a three-electron
complex in three tunable gated quantum dots. The two logical states of a qubit,
|0L> and |1L>, reside in a degenerate subspace of total spin S=1/2 states. We
demonstrate how applying voltages to specific gates changes the one-electron
properties of the structure, and show how electron-electron interaction
translates these changes into the manipulation of the two lowest energy states
of the three-electron complex.
