Analysis of polarization propagation along a semiconductor-based quantum cellular automaton chain

We present a simulation of a chain of three quantum cellular automaton (QCA) cells defined in a GaAs/AlGaAs heterostructure by means of depletion gates, focusing on the evaluation of the voltage unbalance that must be applied to the gates to enforce the correct polarization of the driver cell and propagate it through the other two cells. We use the configuration interaction method in each cell, including the electrostatic coupling between cells with an iterative self-consistent procedure. In particular, we investigate the issue, addressed in the recent literature, of chain malfunction due to the adverse effect on the driven cells of the electric field from the gates defining the driver cell. Our conclusion is that, as long as the gate voltage unbalance polarizing the driver cell is smaller than a threshold depending on geometric and material parameters, correct operation of the QCA wire can be obtained. (C) 2002 American Institute of Physics.