On 20 Sep 2013, at 00:10, LizR wrote:
On 20 September 2013 05:31, John Clark <johnkcl...@gmail.com> wrote:
On Thu, Sep 19, 2013 at 10:18 AM, Bruno Marchal <marc...@ulb.ac.be>
wrote:
>> A computation is a process.
> I can agree with this, unless you meant a "physical process", OK.
As Rolf Landauer said "Computation is physical", all computations
must use energy and generate heat. And what's the difference between
a physical process and a non-physical process anyway?
I thought it was only erasing the results of computations that had
to use energy and increase entropy?
Right. And, as found by Hao Wang a long time ago, you can build
universal system which never erase. (universal = Turing universal).
A good thing, as a universal quantum computer is such a system.
You still need the initial kick in, for macroscopic reversible
universal system, but for microscopic system the energy time
uncertainty can provide it.
With comp, the point is that we have still to explain why the "winner"
seems to be time symmetrical below the substitution level.
- if so - quibbling, I know, but sometimes quibbles have important
consequences.
Sure.
Bruno
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