Re: being inside a universe

From: Hal Finney <>
Date: Fri, 5 Jul 2002 10:40:36 -0700

There was an article recently in New Scientist about a new way to geet
computing beyond the "Turing barrier". I think it is somewhat similar
in spirit to the analog machines, in that it uses infinities, but it is
based on the quantum computing model. The NS article is reprinted at and the original
paper is available at

>From the NS article:

   His suggestion is to think bigger: why not create a superposition
   of every conceivable state at once? Something like a hydrogen atom
   has infinitely many possible energy levels. While the levels start
   out well-spaced, they get closer as the energies grow higher, until
   they become almost indistinguishable. In a paper to be published
   in the inaugural edition of MIT's new journal Quantum Information
   Processing, Calude and Pavlov have shown that a superposition of an
   infinite number of energy states would allow a quantum computer to
   do things no classical computer can ever manage-almost like running
   "forever" in a finite time.

   This leap means that a quantum computer can overcome Turing's most
   famous barrier to computing power: the "halting problem".


   Calude is extremely proud of this result: he believes it could be
   implemented on a real-life quantum computer, laying much that is
   "unknowable" open to attack. "Using infinite superpositions is rather
   theoretical, but not necessarily non-practical or non-testable,"
   he says.

My opinion is that infinite superpositions will never be practical hence
his machine is of only theoretical interest.

Received on Fri Jul 05 2002 - 10:51:44 PDT

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