Design and implementation of finite state machine using quantum-dot cellular automata

Moore's law states that the number of transistors per square inch on integrated circuits has doubled approximately every two years; this is true for CMOS based VLSI circuit design. Quantum-dot cellular automata (QCA) replaces CMOS based VLSI technology. The assembly of quantum dots replaces transistors which is said to be 'quantum-dot cellular automata', an emerging nanotechnology in the field of quantum electronics. Such type of circuit can be used in many digital applications and has an advantage of reduced area utilisation. Quantum mechanics and cellular automata are together said to be QCA. QCA technology has advantages like small size and high speed. CMOS technology uses transistors to create a logic gates but in QCA technology, logic gates and wires are created by using QCA cells. The basic logic gates like AND, OR, inverter, majority gates are implemented. Many combinational and sequential circuits are designed by using these basic gates. This paper aims at the design of finite state machines and its use in vending machine and traffic light controller were discussed. The circuit was designed and the functionality of those was verified using QCADesigner tool.