New designs of reversible sequential devices

TL;DR

This paper presents new optimized reversible sequential circuit designs using a systematic synthesis protocol, demonstrating reduced gate complexity, quantum cost, and feedback loops compared to previous methods.

Contribution

It introduces a clear synthesis protocol for reversible sequential circuits, optimized designs for various latches, and addresses conceptual issues in circuit minimization and optimization.

Findings

Lower gate complexities and quantum costs achieved.

Optimized circuits have fewer garbage bits and feedback loops.

Critique of the artifact nature of gate count reductions with new gates.

Abstract

A clear protocol for synthesis of sequential reversible circuits from any particular gate library has been provided. Using that protocol, reversible circuits for SR latch, D latch, JK latch and T latch are designed from NCT gate library. All the circuits have been optimized with the help of existing local optimization algorithms (e.g. template matching, moving rule and deletion rule). It has been shown that the present proposals have lower gate complexities, lower number of garbage bits, lower quantum cost and lower number of feedback loops compared to the earlier proposals. For a fair comparison, the optimized sequential circuits have been compared with the earlier proposals for the same after converting the earlier proposed circuits into equivalent NCT circuits. Further, we have shown that the advantage in gate count obtained in some of the earlier proposals by introduction of New gates is an artifact and if it is allowed then every reversible circuit block can be reduced to a single gate. In this context, some important conceptual issues related to the designing and optimization of sequential reversible circuits have been addressed. A protocol for minimization of quantum cost of reversible circuit has also been proposed here.