Parallel Multipliers for Quantum-Dot Cellular Automata

This paper explores the optimization of parallel multipliers for Quantum-Dot Cellular Automata. To reduce the complexity, multipliers are designed with quasi-modularity to accommodate large word sizes. The regular quasi-modular product method is used to make n x n multipliers using 4 (n/2 x n/2) modules. This may be continued with further decomposition to 16 (n/4 x n/4) modules, etc. The last two rows in Wallace or Dadda reduction trees are summed by an adder that is 3n/2 - 1 bits long to produce the final product. This design is constructed using coplanar layouts and compared with other QCA multipliers (bit-serial and array multipliers). The delay, area and complexity are compared for several different operand sizes using the QCADesigner simulator.