Re: BIBLE: Quantum computers & Many Worlds Hypoth. (fwd)

Glenn Morton (
Tue, 27 Aug 1996 20:58:28

This is a reply to Joel Cannon, David Campbell, and Loren. I am going to ask
a couple of question since factoring is not my area of specialty.

David Campbell wrote:

>10^500 calculations do not need multiple universes worth of atoms if you
>can recycle them.

I agree. I had somewhat presumed (probably erroneously) that what they were
really meaing was the need for lots and lots of memory for such a problem.
Does anyone know if factoring such large numbers requires large amounts of
memory say more than 10^80 bits (one atom=1 bit)? However, my calculation
below would seem to say that memory is not what is needed.

David wrote:

> However, the idea of multiple universes certainly raises
>interesting theological questions. The problem lies in what "all POSSIBLE
>universes" means. Assuming that all of these universes are under God's
>rule, there are certainly universes which we can imagine but which He
>probably would not allow.

This could raise an analog to the medieval question: Can God create a rock so
big that even He can't move it?

Can God create a universe in which He does not exist? :-)

Obviously, this would be one He would not allow.

Joel Cannon wrote:

>1. I am not familiar with the article (and at the start of a semester
>will not become familiar with it). However, the statement that a
>quantum computer that worked successfully would requre acceptance of
>the many-worlds seems dubious. What is needed to provide evidence is a
>situation where the two pictures provide conflicting
>predictions. Since the yet-to-be-built computer operates using the
>equations of quantum mechanics which are common to any interpretation,
>a one-world situation would give the same answer.
>I suspect the problem is in an implicit assumption that the equivalent
>of 10^500 sequential calculations could not be performed in one
>universe. There is apparently nothing in the equations of QM that
>precludes this.

I believe that you missed the real assumption here. The author was NOT saying
that QM required that 10^500 calculations couldn't be performed in a single
universe. QM doesn't say anything about that. The assumption was that a
calculation (storage and operations) require the manipulation of physical
objects. And there are only so many physical objects in the universe.

Now,the way I calculate things, if each particle could be used only once,
10^500 calculations requires 10^420 universes. Alternatively, assuming that
each particle in each universe (of 10^80 particles) can operate at 10^100
operations per second, then each universe can perform 10^180 operations per
second. This means you need 10^320 seconds to complete the calculation. The
18 billion year old universe is only 10^17 seconds old. Thus you need about
10^300 times as long as the current universe has existed to solve the problem.

If the quantum computer can solve the problem in 5 minutes, where and how did
it perform this magic? Once again, the major premise in that author's
argument was that a calculation required the manipulation of a physical
object. If this is untrue, then his argument fall flat on its face.

Loren Haarsma wrote of Joels dismissal of this problem:

>You are being too kind.
>I would say that the statement was just plain wrong.

I am willing to learn here, Loren. What is wrong with the calculations I
presented above? Once again, it seems to me that the assumption here is the
nature of a "calculation".

I can think of one 'out' for this problem and that would be that the
sub-atomic particles in the universe be used in the calculations. How many
gluons are there in the universe?

Loren wrote:

>If someone knows of a proposed experiment where the many-worlds
>interpretation REALLY makes a different prediction from the standard
>interpretations, I'd be very interested.

I still don't see why this experiment doesn't make a distinct prediction.

Loren wrote:

>So, IMO, those intriguing
>questions about the theological implications of "many-worlds decisions"
>take us beyond science-and-faith into fantasy-and-faith --- a topic
>which I (like J.R.R. Tolkien, C.S. Lewis, Glenn, and George) think is
>worth pursuing occasionally, just so long as we know where we are.

I am in Dallas, which has been a fantasy show on TV. :-)

Foundation,Fall and Flood