Design and realization of efficient quantum cellular automata based novel nano digital architectures

Abstract

A critical issue in Quantum Cellular Automata (QCA) circuit design is establishing crossover between two distinct signal wires. The coplanar and multilayer crossovers were used to construct the QCA circuit architectures and face challenges in fabrication issues and low robustness. The coplanar crossover employs the regular and 450-rotated cells for not communicating with each other which significantly reduces the energy separation between QCA cells due to the task of rotation of QCA cells. However, it requires precise alignment during fabrication to overcome the undesirable fabrication issues. It results to increase the maximum operating temperature, reduces switching time of the QCA circuits and develops resistance to entropy which degrades the circuit performance. The multilayer uses three or five layers of crossover. The distance between two vertical neighboring layers is precisely aligned to transmit the kink energy to that of regularly adjacent cells, but it is difficult to realize. The Clock-Zone-Based Cross Over (CZBCO) addresses coplanar and multilayer crossover issues by employing only regular cells where the clock zones of the wires are shifted by 180O at the crossover and also, achieves high device density. The feed-forward cut-set incorporating CZBCO optimizes the employment of delay and invalidates the crossover issues using regular cells. newlineThe serial adder minimizes the design complexity in terms of area and cell count, while the feed-forward cut-set algorithm alongside CZBCO optimizes the delay and eliminates the crossover issues. The performance of the proposed FIR serial-parallel multiplier is carried out with the modified QCA cost function. QCA-based parallel multipliers such as Dadda and Wallace tree multipliers not only use the huge cell count, increased delay, and larger area but also subject to coplanar fabrication complexity. newline