Optimizing DD-based Synthesis of Reversible Circuits using Negative Control Lines

Synthesis of reversible circuits has attracted the attention of many researchers. In particular, approaches based on Decision Diagrams (DDs) have been shown beneficial since they enable the realization of corresponding circuits for large functions. However, all existing approaches rely on a gate library composed of positive control lines only. Recently, it has been shown that the additional use of negative control lines enables significant reductions of the respective circuit costs. In this paper, we aim for exploiting this potential. To this end, two complementary schemes are investigated. First, a post-synthesis optimization that exploits the power of negative control lines is utilized to optimize the circuits generated by previously proposed DD-based methods. Second, negative control lines are explicitly considered during synthesis. Experimental results demonstrate that the proposed approaches result in a significant reduction with respect to gate count as well as quantum costs.