Critical assessment of the QCA architecture as a viable alternative to large scale integration

We present a quantitative assessment, by means of numerical simulations, of the feasibility of circuits based on the Quantum Cellular Automaton (QCA) paradigm. In particular, we focus on the evaluation of the sensitivity to fabrication tolerances, of the maximum operating temperature, and of the maximum operating frequency. Several approaches to the simulation of QCA devices are discussed and a hierarchical set of tools is presented, from a refined physical model for a single cell to a semiclassical model for relatively large circuits. We also compare the performance of clocked and nonclocked QCA circuits, reaching the conclusion that the clocked implementation is much better suited for computational purposes