Fanout in quantum dot cellular automata

Abstract

In this report, we describe the fabrication and experimental demonstration of fanout in QCA. Fanout is important as it is necessary for complex digital logic circuits and is essential for generating compact designs, as multiple cells can be then driven by a single driver cell. Fanout in QCA is also a direct demonstration of power gain in QCA circuits. The device is realized using metal islands (as quantum dots) and multiple tunnel junctions (MTJs) fabricated using Dolan bridge technique (Fulton, 1987). The circuit consists of three latches, with the latch in the first stage (L1) capacitively coupled to the two latches of the second stage (L2 and L3). The goal of the experiment is to switch L2 and L3 simultaneously using L1 as an input driving both L2 and L3. Each latch is formed by three quantum dots with the middle dot being connected to the end dots by MTJs