Operation of quantum cellular automaton cells with more than two electrons

We present evidence that operation of quantum cellular automaton (QCA) cell s with four dots is possible with an occupancy of 4N + 2 electrons per cell (N being an integer). We show that interaction between cells can be descri bed in terms of a revised formula for cell polarization, which is based onl y on the difference between diagonal occupancies. We validate our conjectur es with full quantum simulations of QCA cells for a number of electrons var ying from 2 to 6, using the configuration-interaction method. (C) 1999 Amer ican Institute of Physics. [S0003-6951(99)04346-6].