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Asynchronous Circuits Using Quantum Dot Arrays
Susumu Adachi

n this paper we propose a wireworld representation of asynchronous circuits composed of a computational universal set of circuit elements consisting of the so-called Rotary Element and the C-JOIN. The Rotary Element has four input and four output lines and two states encoded by a rotation bar, and it redirects a single input signal to one of its output wires depending on its state. The C-JOIN has two input wires, from which it redirects two input signals to its two output wires, but only so if both signals are present. This paper proposes designs of these circuit elements in terms of quantum dot arrays, which facilitate the control of individual electrons.Wires and the C-JOIN can both be implemented through the use of a pumping current. The rotation bar of the Rotary element, on the other hand, is based on the polarization direction in quantum dot-based cellular automata. Switching of the rotation bar occurs due to Coulomb repulsion between an input electron and electrons encoding the polarization of the rotation bar. The correct operation of the proposed design is confirmed by computer simulations.

Keywords: quantum cellular automata, delay-insensitive circuit, rotary element

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