If quantum dots (a) can be fabricated in close proximity, there is the prospect of placing extra electron charges on diagonally opposed dots, forming two logic states. (b) Combined e-beam and FIB lithographic methods for exploring QD assemblies in QCA applications (inset, fov 3x3 um). A schematic representation (c) of a QCA adder circuit. (d) FIB nucleated Ge QDs on a Si (100) surface in a QCA adder circuit geometry (fabricated by MRSEC post-doc Alain Portavoce during a research stay at IBM's T.J. Watson facility).