InterJournal Complex Systems, 24
Status: Accepted
Manuscript Number: [24]
Submission Date: 963011
The physics of computation
Author(s): Franklin Boyle

Subject(s): CX.07

Category: Brief Article


When we refer to the physics of computation, there are two things we can mean. The first is the physics of devices and systems that we interpret to be computing. This is the traditional approach to the physics of computation and what the researchers at this conference generally report on. It involves the application of physics to features and limitations of those systems, such as their capacities to generate particular outputs, the physical limits on size and speed, the amount of energy required to erase a quantity of information, and so on. In essence, it involves applying physics in the usual way---to those quantities which can be measured or have measures defined for them---and so does not address computation per se, only the physics of so-called computing devices and systems. The second meaning, and the one which I explore here, is based on the idea that computation is a particular kind of physical process. Thus the physics of computation in this second sense is about the physics of such a process. The problem, however, is that unlike the first approach, it requires us to know what computation is. As an abstract and intuitive notion, computation has never really been grounded except to the extent that we use it to describe the behaviors of physical systems like digital "computers", analog "computers" and, more often than not, brains. We tend to ascribe it to any system or device which undergoes changes we can interpret as the instantiation of some algorithm. This is, of course, what the first approach to the physics of computation assumes. But to investigate the physics of computation in the second sense, we have to decide which physical process is computation, not the physics of devices we say are computing just because we can map some algorithm onto their physical behaviors.

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