Abstract
We study the operation of quantum cellular automata (QCA) devices in the presence of stray charge. The operation of linear arrays of QCA cells, called binary wires, relies on Coulombic interaction between the cells, which is affected by the presence of such stray charge. The position of the charge determines whether or not the devices function properly, and it is possible to determine the "forbidden" region near the array in which the presence of stray charge causes device failure. We calculate this forbidden region by directly diagonalizing the Hamiltonian for the system including the stray charge. We find that the QCA binary wire is unaffected by stray charge at a distance greater than the intercellular repeat distance of the wire.