Optimized area efficient quantum dot cellular automata based reversible code converter circuits: design and energy performance estimation

Quantum-dot cellular automata (QCA) based circuit designs are creating a surge in transistorless computational technologies. Due to its quasi-adiabatic switching resulting in extremely low leakage power dissipation as there is no continuous path. These circuits also enjoy extremely high packaging density of the order of 10(12) devices/cm(2) because of its extremely scaled area of 18 nm x 18 nm along with very high 100 GHz frequency of operation. Further the loss of bit information could be abolished by reversible logic computing. This thereby realizes an energy efficient logic operations owing to bijective relation between inputs and outputs in reversible logic. This work investigates the code converter circuits which converts 4-bit binary code to excess-3 code and vice versa based on reversible QCA logic gates for the first time. Moreover an area efficient design for 4-bit binary to gray and vice-versa code converters also designed here. All these four code converter circuits are designed using reversible logic gate Feynman and Peres gates by deploying the QCA Designer and Designer-E tool v2.0.3. Finally the in depth performance estimation of the proposed circuits in terms of circuit complexity, quantum cost and energy dissipation are also presented here. Moreover, these QCA based circuits provide a strong evidence that reversible logic based QCA circuits can be efficiently deployed for these code converter circuits.