Programmable Synchronous 2-Bit Counter in Quantum-Dot Cellular Automata

Quantum-dot Cellular Automata (QCA) is a newly-developed nanoscale electron device that has the potential to replace the conventional transistor in the future. Owing to the unique field-coupling mechanism of QCA, several constraints must be fulfilled during the design of QCA sequential circuits, which makes the construction of sequential circuits a relatively intractable issue in QCA research. In this paper, a programmable synchronous 2-bit counter in QCA is proposed, which is consisted of combinational logic and falling edge-triggered JK flip-flops. The count mode of the programmable counter can be changed on-demand by mode control signals. Moreover, an initial state setting method of the QCA circuit is also proposed during the design of the counter so that the effects of random initial states can be avoided. Simulation with QCADesigner software demonstrates the validity of the proposed counter.