A reversible approach to two's complement addition using a novel reversible TCG gate and its 4 dot 2 electron QCA architecture

Classical computers are already facing threshold limitations with CMOS getting restricted to clocking speeds in GHz range and alarming heat dissipation issues. Both these issues have been addressed by Quantum Dot Cellular Automata (QCA) and the concept of reversibility. QCA has showcased clocking speed in THz range and reversibility addresses the heat dissipation issues; thereby providing a viable alternative to CMOS. Reversibility forms an integral part of Quantum Computers. At present QCA happens to be the globally accepted practical platform for realization of reversible architecture concepts. This communication presents a novel four variable reversible gate which is capable of generating the two's complement of a four bit number. Two's complement finds wide acceptance in addition intensive environments. By the virtue of the Boolean expressions involved in designing the proposed gate, our gate also plays a crucial role in XOR intensive operation. We have done a comparative analysis with existing proposals in literature and found the proposed gate to excel. In this communication we also present the utility of our proposed gate in designing sequential circuits, primarily flip-flops.