Automatic Cell Placement for Quantum-dot Cellular Automata

Quantum-dot Cellular Automata (QCA) is a novel computing mechanism that can represent binary information based on spatial distribution of electron charge configuration in chemical molecules. It has the potential to allow for circuits and systems with functional densities that are better than end of the roadmap CMOS, but also imposes new constraints on system designers. In this paper we develop the first cell-level placement of QCA circuits, where the given circuit is assumed to be partitioned into 4-phase asynchronous QCA timing zones. We formulate the QCA cell placement in each timing zone as a unidirectional geometric embedding of k-layered bipartite graphs. We then present an analytical and a stochastic solution for minimizing the wire crossings and wire length in these placement solutions