In that 1997 book, David Deutsch has a fascinating perspective.1 It’s one that I share, and it goes against the prevailing understanding of most computer scientists, mathematicians, and pretty much anyone who has even a minimal background in the theory of computation. For them, computation was defined more than 80 years ago by Alan Turing.2 The edifice researchers have built on it—which has led, among other things, to our modern computers—is quite impressive. Those researchers would tell you that the only physics necessary in the field of computation is the one that makes Turing’s ideas practical. That is, physics is just a tool to realize in practice the mathematical concept that Turing envisioned: With better transistors, engineers can make our modern computers faster, more energy efficient, and smaller.
What if instead we take Deutsch’s viewpoint more seriously? In that case, what physics should we use to compute? Deutsch...
