> On 5/5/2001, Hal Finney wrote:
> >A reversible computer is as likely to take a step backwards as forwards.
> >So even if it manages to complete a calculation from A to B, the process
> >will be a random walk, moving forward and backwards many times over each
> >portion of the path from A to B.
> I think you mean to say that it is *nearly* equally likely to take
> steps in either direction. There needs to be some small bias to get
> something predictable to happen.
Yes, although the bias can in principle be as small as you like, depending
on how long you want it to wait. I wonder what it would be like if you
were implemented on a computer with no bias? I guess the question is how
far it would get via random walk before the computer falls apart (sqrt(t)
steps after time t). But using zero energy has enough advantages that
maybe in some circumstances you would risk it.
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