From: Wayne Hayes (wayne@cs.toronto.edu)
Date: Sun Dec 14 1997 - 10:24:37 MST
John K Clark <johnkc@well.com> writes:
>Nonsense, if classical physics was correct matter wouldn't even be stable.
We're arguing at cross purposes here. I have no argument with this
statement. Of course QM is a better approximation than classical
mechanics. (We don't know that it's perfect, but it's certainly
a better approximation.) My point is that, for the MACROSCOPIC
observable properties of most objects to be duplicated, quantum
information is not needed. A classical description is good enough.
And, as far as I understand how brains work, everything in your mind
that defines who you are is encoded in chemical bonds that can be
described classically. Physicists and chemists that study molecular
dynamics often use only classical descriptions of the particles.
(This is very close to my research area, so I can make this particular
statement flatly, and know it's true.)
I am *not* claiming that we don't need to know anything about QM to
have teleportation; I'm claiming that there are properties that need
not be duplicated in order to produce a FUNCTIONALLY identical
duplicate. Spin, for example, is probably one of the things that
doesn't need to be duplicated. And since spin is the only thing
they've claimed to have duplicated, I think calling this process
"teleportation" is a very bad choice of name.
>All states are quantum states. Classical states are only approximations,
>sometimes good and sometimes very bad approximations of quantum states.
See above. I agree. The question is whether we *need* the approximations
to be better than classical in order to duplicate the macroscopic properties
of objects. (By "macroscopic" I mean anything bigger than an atom.)
> >a *completely identical* brick, in all respects down to every last
> >atom in every position, except the quantum state of all its
> >constituent atoms and molecules
>Is this a riddle? How can two bricks be completely identical except for being
>totally different down to the very smallest detail?
We can describe the position of every atom in the brick relative to
every other atom without resorting to QM. If you duplicate that, I
claim that you have a functionally identical brick. I don't care what
the spin states are of the atoms in my brick, as long as it can still
be used to build my house. Similarly, I don't care about the spin
states of the atoms in my brain, as long as my memories and personality
and everything else about my mind is duplicated. And as I believe
MRI scans prove, the spin states of the atoms are indeed irrelevant to
to workings of the brain.
>I think the enormous magnetic field in the largest MRI machines can be
>detected by some people, I don't claim this fact has any great relevance to
>this discussion however.
That's interesting, I hadn't heard that some people claim to be able to
detect the field. However, I don't know how I can state the relevance
any plainer than I did already: MRI scans make dramatic changes to the
brain at the quantum level, and yet the brain's functioning is not
affected. I think that's clear evidence that spin information, at least,
is not relevant to the brain's working.
>A photon has a well defined momentum and energy, if those weren't
>duplicated then quantum teleportation has not happened, I've not read the
>article in Nature yet but apparently it has happened, unless fraud has been
>committed and I doubt that.
I browsed the original article several months ago. The only
property that was duplicated was spin. I don't recall that it was
actually photons; if that was the case, it would have been polarization
that was duplicated. In any case, the process doesn't "duplicate"
energy because the photon already needs to exist at the destination
and as I've stated several times already, this process does not
change the energy of anything at the destination. And it doesn't
duplicate momentum either. (That wouldn't be very useful if you
wanted to teleport something into a reference frame moving at a
different velocity, would it?) They've only dulplicated polarization
(or spin).
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