On polymorphic logical gates in sub-excitable chemical medium

TL;DR

This paper demonstrates that a light-sensitive Belousov-Zhabotinsky chemical medium can perform polymorphic logical operations, with collision outcomes controlled by illumination, enabling universal computation in a chemical system.

Contribution

It introduces collision-based polymorphic logical gates in a chemical medium, showing how illumination controls gate functions and demonstrating computational universality.

Findings

Wave-fragment collisions can be controlled by illumination levels.

The medium can implement XNOR and NOR gates depending on light conditions.

The system exhibits computational universality through chemical reactions.

Abstract

In a sub-excitable light-sensitive Belousov-Zhabotinsky chemical medium an asymmetric disturbance causes the formation of localized traveling wave-fragments. Under the right conditions these wave-fragment can conserve their shape and velocity vectors for extended time periods. The size and life span of a fragment depend on the illumination level of the medium. When two or more wave-fragments collide they annihilate or merge into a new wave-fragment. In computer simulations based on the Oregonator model we demonstrate that the outcomes of inter-fragment collisions can be controlled by varying the illumination level applied to the medium. We interpret these wave-fragments as values of Boolean variables and design collision-based polymorphic logical gates. The gate implements operation XNOR for low illumination, and it acts as NOR gate for high illumination. As a NOR gate is a universal gate then we are able to demonstrate that a simulated light sensitive BZ medium exhibits computational universality.