> On 1 May 2019, at 19:58, [email protected] 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] <javascript:> 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 <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 > > - @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] > <mailto:[email protected]>. > To post to this group, send email to [email protected] > <mailto:[email protected]>. > Visit this group at https://groups.google.com/group/everything-list > <https://groups.google.com/group/everything-list>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- 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.
