On 1 May 2019, at 19:58, cloud...@gmail.com <javascript:> wrote:
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 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?
