On Wednesday, May 1, 2019 at 11:30:20 AM UTC-5, Bruno Marchal wrote: > > > On 1 May 2019, at 10:56, cloud...@gmail.com <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 > > *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.
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