Missing-cell defects in QCA wires: The ground and excited electronic states perspectives

Abstract

Quantum Cellular Automata (QCA) technology offers promising prospects for designing molecular electronic circuits that operate at high frequencies and with ultra-low power consumption. QCA wires serve as crucial conduits for digital data transmission between logic gates. A series of QCA cells arranged sequentially forms these wires, with data written or read using paired nanogap electrodes. In this study, employing a simplified full-basis quantum mechanical model, we investigate the impact of single and double missing cells on the response function and output voltage of wires implemented within the two-dot QCA architecture. The electronic coupling between the quantum dots within each QCA cell stands out as a critical structural parameter influencing both the nonlinearity of the response function and the level of output voltage. Ground state analyses of wires affected by missing-cell defects suggest that employing QCA cells with weak electronic coupling could potentially enhance fault tolerance. However, examination of excited states reveals that reducing electronic coupling may compromise the thermal robustness of such defective QCA wires.