On Thursday, May 2, 2019 at 10:18:33 AM UTC-5, Bruno Marchal wrote: > > > On 1 May 2019, at 19:58, [email protected] <javascript:> wrote: > > > > On Wednesday, May 1, 2019 at 11:30:20 AM UTC-5, Bruno Marchal wrote: >> >> >> On 1 May 2019, at 10:56, [email protected] wrote: >> >> >> >> By "heat" I just mean it as one studies it as a subject in a physics >> class, for example. >> - https://en.wikipedia.org/wiki/Heat >> >> *Does all computation generate heat?* >> >> (Should be a simple enough question, I think.) >> >> >> Hmm… Not that simple. In the 1950s, Hao Wang has given the first proof >> that there exist universal machine working in a completely reversible way, >> without any erasing of information. Wang was a mathematical logicien, and >> his result was ignored. >> >> In 1961, Landauer, a physicist, working on the Maxwell Daemon problem, >> discovered that the only computational process that generates heat is the >> erasure. To erase 1 bit of information Landauer shows that you need to >> dissipate at least kTln(2) energy, with k the Boltzman constant and T the >> temperature. >> >> So, in principle, given Hao Wang + Landauer, we can build a machine doing >> computation without using, nor dissipating any energy, except for the start >> and ending of the computation. >> >> Then, most algorithm in quantum computing require full reversibility, and >> should work with very few amount of energy, except similarly for the local >> read and write, or starting vs stopping behaviour. >> >> Both from mechanism and physics, I conjecture that there is a core >> physical reality which is a BCI algebra, which means no erasure of >> information, and no duplication of information. This CANNOT be Turing >> universal, and it is unclear to me which of erasure and duplication can be >> truly physical. It is just well above the scope of the present knowledge of >> the machine’s physics to answer this, and among physicians, this leads to >> discussion of black hole, non cloning theorem, etc. Open problem for me. >> >> Of course, in arithmetic, no computation at all use energy, given that >> they use only the arithmetical truth, which are out of time and space, and >> any physical category. The physics emerge from this, as an invariant >> pattern for all Turing universal observation, defined by a sort of bet on >> first person experiences. Energy should be retrieved from that Core >> physics. I speculate that the Monster Group plays a role here. >> >> Bruno >> >> >> >> >> - @philipthrift >> >> > In the curious case of quantum computation, it seems it may be the case > that there is no heat generated until a "measurement" is made. > > Is that right? > > > That is right, unless you are using a special quantum algorithm which does > “measurement” during the computation. But if not, then the computation > corresponds to a unitary, completely reversible, process, and no heat is > generated. > > Bruno > > > > A related question to my original ("Does all computation generate heat?"):
Does consciousness generate heat? @philipthrift -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
