Re: Quantum Computers

From: Doug Jones (random@qnet.com)
Date: Tue Aug 17 1999 - 11:46:23 MDT


John Clark wrote:

> In another book called "The Ghost In The Atom" Deutsch does give what
> he considers a definitive test of the Many World Interpretation and
> a Quantum Computer is part of it, but it must be intelligent.
>
> In the Deutsch test a conscious quantum computer shoots electrons
> at a metal plate that has 2 small slits in it. It does this one
> at a time. After leaving the plate the electrons hit some
> photographic film, but do not look at the photograph until
> later. The quantum mind has detectors near each slit so it
> knows which slit the various electrons went through.

There's your fallacy- detectors at the slits perturb the wave
function of the electrons, and destroy the interference pattern.
It's the detector, not whatever looks at the *output* of the
detector, that matters. Erasing the recording of the output does
not eliminate the interaction that the detector had with the
electrons earlier.

The rest of the handwaving is pointless.

> The quantum mind now signs a document saying that it has observed
> each and every electron and knows what slit each electron went
> through.

[snip]
 
> In the Copenhagen interpretation when the results of a
> measurement enters the consciousness of an observer the wave
> function collapses,

No, when the measurement is *made* by any brainless piece of
machinery (via intereaction via photons or other particles), the
wave function collapses. This can be demonstrated by placing a
detector in a two-slit experiment, and not connecting the output to
anything. The interference pattern goes away regardless.

> in effect all the universes except one disappear without a trace
> so you get no interference. In the many worlds model all the other
> worlds will converge back into one universe when the electrons hit
> the photographic film but their influence will still be felt,
> you'll see indications that the electron went through slot A only
> and indications that it went through slot B only, and that's
> what causes interference. Time will tell who's correct.

Nope- if a detector is placed on either slit, the interference
pattern goes away. *Only* if there is no measurement made at either
slit can an interference pattern occur. No mumbo jumbo, no
half-dead cats.

--
Doug Jones, Freelance Rocket Plumber


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