Efficient design and implementation of approximate FA, FS, and FA/S circuits for nanocomputing in QCA

Area of Science:

• Quantum computing
• Nanotechnology
• Digital circuit design

Background:

• Quantum Cellular Automata (QCA) offers low power, low latency, and compact designs.
• Approximate arithmetic is a key paradigm for low-power, high-performance computing.
• XOR gates are fundamental building blocks for digital circuits and QCA technology.

Purpose of the Study:

• To present new Quantum Cellular Automata (QCA)-based approximate circuits using XOR logic.
• To develop approximate full adders (FA), full subtractors (FS), full adder/subtractors (FA/S), and 4-bit ripple carry adders (RCA).
• To design circuits with improved cell utilization and accessibility.

Main Methods:

• Design and implementation of novel QCA circuits for approximate FA, FS, FA/S, and 4-bit RCA.
• Utilizing XOR logic as the core component for circuit construction.
• Functional verification and performance evaluation using the QCADesigner program.

Main Results:

• Achieved a delay of 0.5 clock phases and an area of 0.01 μm2 for approximate FA and FS designs using 11 cells.
• Developed approximate FA/S designs with 0.5 clock phase delay, 0.01 μm2 area, and 12 cells.
• Proposed an approximate 4-bit RCA using 64 QCA cells.
• Demonstrated significant improvements over previous designs in speed and space, with cell count reductions of 21% for FA and FS, and 43% for RCA.

Conclusions:

• The proposed QCA-based approximate arithmetic circuits are effective and efficient.
• The new designs offer superior performance in terms of speed and area compared to existing solutions.
• These advancements contribute to the development of low-power, high-performance QCA computing systems.