  Using electrostatic gates to control the electron positions, we present a new
controlled-NOT gate based on quantum dots. The qubit states are chosen to be
the spin states of an excess conductor electron in the quantum dot; and the
main ingredients of our scheme are the superpositions of space-time paths of
electrons and the effect of Coulomb blockade. All operations are performed only
on individual quantum dots and are based on fundamental interactions. Without
resorting to spin-spin terms or other assumed interactions, the scheme can be
realized with a dedicated circuit and a necessary number of quantum dots. Gate
fidelity of the quantum computation is also presented.
