Simulating the Fredkin Gate with Energy-Based P Systems

Reversibility plays a fundamental role when the possibility to per- form computations with minimal energy dissipation is considered. Many pa- pers on reversible computation have appeared in literature: the most famous are certainly the work of Bennett on (universal) reversible Turing machines and the work of Fredkin and To®oli on conservative logic. The latter is based upon the Fredkin gate, a reversible and \conservative" (according to a de¯nition given by Fredkin and To®oli) three{input/three{output boolean gate. In this paper we introduce energy{based P systems as a parallel and distributed model of computation in which the amount of energy manipulated and/or consumed during computations is taken into account. Moreover, we show how energy{based P systems can be used to simulate the Fredkin gate. The proposed P systems that perform the simulation turn out to be themselves reversible and conservative.