Synthesis of Reversible Synchronous Counters

Reversible logic is very important in low-power circuit design and quantum computing. Though a significant number of works has been done on reversible combinational logic synthesis, only few papers have been published on reversible sequential logic synthesis and per mutative quantum automata. The reported works on reversible sequential logic discuss designs of reversible flip-flops and suggest synthesizing reversible sequential circuits by replacing the flip-flops and combinational parts of traditional sequential circuit designs by their reversible counterparts. In this paper, we discuss direct design of reversible synchronous counters based on positive polarity Reed-Muller expressions. Design results show that the direct design method is more efficient than the replacement method. The method can be also applied to per mutative quantum automata that have quantum memories external to the circuit.