Evaluation and Improvement of Approximate Multipliers in Quantum-Dot Cellular Automata (QCA)

نوع: Type: Thesis

مقطع: Segment: masters

عنوان: Title: Evaluation and Improvement of Approximate Multipliers in Quantum-Dot Cellular Automata (QCA)

ارائه دهنده: Provider: Shobeir Fayazi

اساتید راهنما: Supervisors: Hatam Abdoli

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: Abbas Ramezani, Mehdi Abbasi

زمان و تاریخ ارائه: Time and date of presentation: 2026

مکان ارائه: Place of presentation: سالن سمینار گروه کامپیوتر

چکیده: Abstract: Quantum-dot cellular automata (QCA) is a promising beyond-CMOS nanotechnology for ultra-low-energy digital systems; however, designing multipliers with simultaneously low layout cost and low energy dissipation is still challenging. In parallel, approximate arithmetic enables a controlled trade-off between bounded accuracy and significant reductions in area, latency, and energy for error-resilient applications. This work proposes a family of QCA-oriented approximate multipliers based on majority logic. At the Boolean level, an approximate 2×2 multiplier tile is defined with only one mismatch out of sixteen input patterns (6.25% error rate), and an approximate 4:2 compressor is defined with five mismatches out of 32 patterns (15.6% error rate), with deviations restricted to low-weight combinations. Two QCA implementations of the 2×2 tile are then developed: a compact coplanar single-layer layout and a regular three-layer multilayer layout. The 4:2 compressor is implemented in QCA and used to build an approximate 4×4 multiplier by tiling the 2×2 blocks. Designs are evaluated in QCADesigner-E under a unified setup using cell count, area, latency, cost, efficient complexity, and energy dissipation, demonstrating substantial improvements over representative prior QCA multiplier and compressor designs.

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