Lo these many years ago, I blogged about how a paper of John Norton's had led me to have doubts about Landauer's Principle. Prof. Norton has continued to work on this topic, and I am very happy to share the news about his upcoming talk at CMU's "Energy and Information" seminar:
(For the record, I remain of at least two minds about Landauer's principle. The positive arguments for it seem either special cases or circular, but the conclusion makes so much sense...)
Manual trackback / update, 1 April 2014: Eric Drexler's Metamodern, who objects that "the stages of computation themselves need not be in equilibrium with one another, and hence subject to back-and-forth fluctuations" (his italics). In particular, Drexler suggests introducing an external time-varying potential that "can carry a system deterministically through a series of stages while the system remains at nearly perfect thermodynamic equilibrium at each stage". But I think this means that the whole set-up is not in equilibrium, and in fact this proposal seems quite compatible with sec. 2.2 of Norton's "No-Go" paper. Norton's agrees that "there is no obstacle to introducing a slight disequilibrium in a macroscopic system in order to nudge a thermodynamically reversible process to completion"; his claim is that the magnitude of the required disequilibria, measured in terms of free energy, are large compared to Landauer's bound. The point is not that it's impossible to build molecular-scale computers (which would be absurd), but that they will have to dissipate much more heat than Landauer suggests. I won't pretend this settles the matter, but I do have a lecture to prepare...
Posted at March 15, 2014 11:25 | permanent link