When does a physical system compute?

Horsman, Clare; Stepney, Susan; Wagner, Rob C.; Kendon, Viv

Abstract

Computing is a high-level process of a physical system. Recent interest in non-standard computing systems, including quantum and biological computers, has brought this physical basis of computing to the forefront. There has been, however, no consensus on how to tell if a given physical system is acting as a computer or not; leading to confusion over novel computational devices, and even claims that every physical event is a computation. In this paper, we introduce a formal framework that can be used to determine whether a physical system is performing a computation. We demonstrate how the abstract computational level interacts with the physical device level, in comparison with the use of mathematical models in experimental science. This powerful formulation allows a precise description of experiments, technology, computation and simulation, giving our central conclusion: physical computing is the use of a physical system to predict the outcome of an abstract evolution. We give conditions for computing, illustrated using a range of non-standard computing scenarios. The framework also covers broader computing contexts, where there is no obvious human computer user. We introduce the notion of a ‘computational entity’, and its critical role in defining when computing is taking place in physical systems.

Citation

Horsman, C., Stepney, S., Wagner, R. C., & Kendon, V. (2014). When does a physical system compute?. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 470(2169), Article 20140182. https://doi.org/10.1098/rspa.2014.0182

• Journal Article Type: Article
• Acceptance Date: Jun 11, 2014
• Online Publication Date: Sep 8, 2014
• Publication Date: Sep 8, 2014
• Deposit Date: Nov 5, 2014
• Publicly Available Date: Nov 12, 2014
• Journal: Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
• Print ISSN: 1364-5021
• Electronic ISSN: 1471-2946
• Publisher: The Royal Society
• Peer Reviewed: Peer Reviewed
• Volume: 470
• Issue: 2169
• Article Number: 20140182
• DOI: https://doi.org/10.1098/rspa.2014.0182
• Keywords: Computation, Physical computation, Computer.
• Public URL: https://durham-repository.worktribe.com/output/1418260