Regular realization of symmetric functions using reversible logic

Abstract

Reversible logic is of increasing importance to many future computer technologies. We introduce a regular structure to realize symmetric functions in binary reversible logic. This structure, called a 2*2 net structure, allows for a more efficient realization of symmetric functions than the methods introduced by the other authors. Our synthesis method allows us to realize arbitrary symmetric function in a completely regular structure of reversible gates with relatively little "garbage". Because every Boolean function can be made symmetric by repeating input variables, our method is applicable to arbitrary multi-input multi-output Boolean functions and realizes such arbitrary function in a circuit with a relatively small number of additional gate outputs. The method can also be used in classical logic. Its advantages in terms of numbers of gates and inputs/outputs are especially seen for symmetric or incompletely specified functions with many outputs.