  Taking the excess electron spin in a unit cell of semiconductor multiple
quantum-dot structure as a qubit, we can implement scalable quantum computation
without resorting to spin-spin interactions. The technique of single electron
tunnelings and the structure of quantum-dot cellular automata (QCA) are used to
create a charge entangled state of two electrons which is then converted into
spin entanglement states by using single spin rotations. Deterministic
two-qubit quantum gates can also be manipulated using only single spin
rotations with help of QCA. A single-short read-out of spin states can be
realized by coupling the unit cell to a quantum point contact.
