A reversible carry-look-ahead adder using control gates

In principle, any reversible logic circuit can be built by using a single building block (having three logic inputs and three logic outputs). However, no simple synthesis tool is available to tell us how a particular logic operation has to be composed of such unit. We demonstrate that, for a flexible design, it is more advantageous to use a broad class of reversible gates, called control gates. They form a generalization of Feynman's three gates (i.e. the NOT, the CONTROLLED NOT, and the CONTROLLED CONTROLLED NOT). As an illustration, a 320-transistor reversible 4-bit carry-look-ahead adder in 0.8 mum c-MOS has been built. (C) 2002 Elsevier Science B.V. All rights reserved.