Reversible Logic Design Using QCA: Challenges and Future Aspects
Rupali Singh, Devendra Kumar Sharma · Apple Academic Press eBooks · 2021
Computation using low-power, high-density, and high-speed circuits is the utmost necessity of nanoscale systems. Technology is changing overnight, and the size of the transistor is shrinking day by day. Complementary metal-oxide-semiconductor (CMOS) technology is approaching its limits due to leakage currents, power consumption, difficulties in lithography, etc. Thus, some alternative solution has to be obtained to overcome CMOS limitations and potentially replace CMOS circuits. Reversible logic and quantum-dot cellular automata (QCA) have emerged as promising paradigms which can excel in performance and possible substitute of CMOS in nano-circuits. A reversible logic can be used in the circuits to nullify the energy dissipation during computation. Reversibility is introduced in the circuit by replacing irreversible gates with reversible one. On the other hand, QCA makes use of nanostructures called quantum dots, to build the circuits with compact size, ultra low power, and faster processing capability. This chapter focuses on the major aspects of reversible quantum circuits including basic to the complex structures with their comprehensive analysis. This study targets the design of combinational and sequential circuits using a reversible logic. For that, a unique reversible gate is proposed that can be solely used to design combinational as well as sequential circuits. The reversible gate is implemented in QCA and further subjected to various analyses such as cost analysis, fault characterization, and power analysis. The proposed reversible gate is further utilized to design combinational circuits such as adder, subtractor, and multiplexer, and sequential circuits such as latches and shift 32 register. Moreover, the reversible circuits are analyzed for QCA parameters such as the number of QCA cells, latency, and cost function. Subsequently, this work presents a complete exploration of reversible QCA circuits from basic theory to all-around analysis.