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Quantum-dot cellular automata (QCA) is the best-suggested nanotechnology for designing digital electronic circuits. It has a higher switching frequency, low-power expenditures, low area, high speed and higher scale integration. Recently, many types of research have been on the design of reversible logic gates. Nevertheless, a high demand exists for designing high-speed, high-performance and low-area QCA circuits. Reversible circuits have notably improved with developments in complementary metal–oxide–semiconductor (CMOS) and QCA technologies. In QCA systems, it is important to communicate with other circuits and reversible gates reliably. So, we have used efficient approaches for designing a $3\times 3$ reversible circuit based on XOR gates. Also, the suggested circuits can be widely used in reversible and high-performance systems. The suggested architecture for the $3\times 3$ reversible circuit in QCA is composed of 28 cells, occupying only 0.04$\mu$m². Compared to the state-of-the-art, shorter time, smaller areas, more operational frequency and better performance are the essential benefits of the suggested reversible gate design. Full simulations have been conducted with the utilization of QCADesigner software. Additionally, the proposed $3\times 3$ gate has been schematized using two XOR gates.

Quantum-dot cellular automata (QCA) technology is one of the nanotechnologies which attracted a great deal of consideration because of features like the speed of the circuit, low-power utilization and small size. In digital electronics, the comparator plays a vital role, due to its vast area of applications like state machine design, digital testing and fault tolerance, digital control systems, etc. This paper proposes a 4-bit/8-bit/16-bit comparator in QCA technology using the XOR Gate. The proposed method is an efficient method, which has two stages: finding whether the inputs are equal or not in stage 1 and less than or greater than in stage 2 using an XOR gate. The proposed comparator circuits have less area and cost with less delay as compared to the previous works. The proposed energy calculations are carried out with the QCA DesignerE tool, and it is observed that the proposed structures are energy efficient. In addition, the proposed comparators are simulated and synthesized with Vivado design suite 2021.1 and implemented on the Virtex UltraScale VCU129-PP FPGA board.

We propose a new and potentially integrable scheme for the realization of an all-optical binary full subtractor employing two half-subtractors and an additional OR gate. The half-subtractor comprises an XOR gate, an AND gate, and a NOT gate. The XOR gate is realized using semiconductor optical amplifier (SOA)-based Mach–Zehnder interferometer (MZI). The AND, OR, and NOT gates are based on nonlinear properties of semiconductor optical amplifier. The proposed scheme is driven by two input data streams and a borrow bit from the previous less significant bit order position. In our proposed design, we achieve extinction ratios for difference and borrow output signals of 11dB and 10dB, respectively. Successful operation of the system is demonstrated at 10Gb/s return-to-zero modulated signals.

A new transistor-less field-coupled nanocomputing (FCN) method for ultra-scale “nanochip” integration is called quantum-dot cellular automata (QCA). Electrostatic repulsion between electrons and the electron tunneling process in quantum dots is employed in QCA to depict digital circuitry. QCA technology is able to achieve higher clock speed, lower occupied chip area, and more energy efficiency than traditional complementary metal-oxide semiconductor (CMOS) technology. Irreversible majority gates are commonly utilized as the main building blocks in the development of QCA circuits. In order to create highly energy-efficient QCA circuits, some research has recently presented digital image processing design strategies that use majority gates as the primary building block. Image processing, which encompasses picture analysis, enhancement, and correction, is used to extract information from images and improve their quality. Among the primary methods for processing images are picture enhancement, restoration, compression, object recognition, and machine vision applications. However, morphological procedures such as dilation and erosion constitute the fundamental component of image processing and are widely applied in practical applications. In this study, QCA-optimized nanostructures are presented for applications in mathematical morphology, serving as erosion and dilation operators. The completed circuit comprises 33 cells and exhibits a temporal delay of approximately 0.75 during each clock cycle. A comparison with the best equivalent nano-architecture demonstrates a significant improvement in cell performance, scalability, and latency.