In this article, the basic concepts of our recently proposed computing architecture based on Coulomb coupling of nanofabricated structures, called quantum cellular automata (QCA) are reviewed and fabrication issues critical to the new technology are discussed. The QCA fabrication will require an extremely high level of lithographic control. To this end, the proximity effects in making very high density patterns with poly(methylmethacrylate) (PMMA) and electron-beam lithography have been experimentally investigated. A triple Gaussian model was used to simulate the experimental data. By using a 50 keV electron beam, sub-40 nm pitch gratings, double lines, and dot grids were successfully fabricated on Si and SiO2/Si bulk wafers with single-level PMMA and lift-off.