The current research goal is set to provide efficient design and a practical arrangement of the multiplexer, D-latch, and shift register in the quantum-dot cellular automata (QCA) technology. In the proposed multiplexer, including 14 cells, an area of 0.01 , a 0.5 clock cycle delay, and an energy consumption of 17.31 meV, the number of cells and energy consumption rates are reduced by 6.66 and 7.53% compared to the previous designs. Also, a D-latch is designed in this paper using the proposed multiplexer, which has been improved dramatically compared to the previously proposed methods. The proposed D-latch with 24 cells, an area of 0.02 meV, a 0.5 clock cycle delay, and energy consumption of 26.18 meV reduced the delay and energy consumption rates, respectively, by 50 and 16.14% in comparison with the best previous designs. The reset and set terminals are also added to the proposed D-latch. The designed D-latches were used in a 4-bit shift register to demonstrate their accurate functioning in more complicated circuits. Accordingly, a 14.28% delay rate reduction resulted. Also, the proposed shift register contains 149 cells, an area of 0.11 meV, a 1.5 clock cycle delay, and an energy consumption of 156.05 meV . The simulation of the proposed circuits was made by QCADesigner and QCAPro tools.
