The Design of a Surface Atomic Scale Logic Gate with Molecular Latch Inputs

Two-input/one-output atomic scale Boolean logic gates are presented which are supposed to be atom by atom STM constructed on an Si(100)H-passivated surface. For those relatively simple logic gates, semi-classical and quantum Hamiltonian computing (QHC) architectures are compared showing how the QHC design avoids long atomic scale wiring compulsory for any classical or semi-classical "a la Shannon" electric circuit design. For a more realistic approach, the simple double hydrogen switching elements used for the logical inputs were substituted by mechanical molecule latch inputs. This does not transform the logical Boolean truth tables of the surface-implanted logic gates. For both the semi-classical and the QHC designs, the four standard known Boolean logic gates: AND, NOR, NAND and OR can be formally designed with an exception of the OR for the QHC approach. On the surface, AND, NOR, NAND and OR can be implanted in a semi-classical way and NOR and OR in a QHC way. For QHC, the re-emerging of the OR is due to through-surface electronic couplings, which is inducing a dependence between the inputs and the structural parameters of the QHC gates.