Sekwencyjne odwracalne układy logiczne

Układy odwracalne realizują wzajemnie jednoznaczne odwzorowania sygnałów wejściowych na sygnały wyjściowe, tj. nie prowadzące do straty informacji. Badania nad tymi układami prowadzone są bardzo intensywnie. Początkowo zajmowano się głównie syntezą kombinacyjnych układów, dopiero w ostatnich latach liczba publikacji na temat sekwencyjnych układów wzrosła. W pracy przedstawiono układy odwracalnych zatrzasków, które zaproponowano w literaturze, i sformułowano otwarte problemy w tej dziedzinie.

Reversible computations stretch the limits of the classical computa-tions, bounded otherwise by energy loss. They are also the basis for the emerging quantum technologies. Though such designs have succeeded since they are logically equivalent with classical designs, there is still much room for improvement. Reversible logic circuit synthesis received much attention in the past decade from the computer science community due to its, as yet unrivaled, potential to satisfy the requirements for power efficient computations. The initial focus has been given to the combinational logic circuits, as the foundation of a general theory for the reversible circuit synthesis. Recently, more attention is given to sequential circuits as they form the basis of the well known state-based processing of the traditional computers. The research in this field started in 1980 with the pioneering work of Toffoli [3], followed only in 1996 by Picton [7]. Next publications by Chuang and Wang [8], and Rice [9] appeared in the last decade, followed by some very recent publications, e.g. Banerjee and Pathak [10]. This paper gives an overview of the current advances in the field of the sequential reversible logic presenting latches, the most common sequential circuits, and open problems.