From: bhv@areaplg2.corp.mot.com (Bronis Vidugiris)
Subject: Re:  Simple observation about Quantum Kitty Cats
Organization: Motorola, CCR&D, CORP, Schaumburg, IL
Date: Fri, 2 Oct 1992 17:14:16 GMT

In article <1992Oct2.052956.15760@asl.dl.nec.com> terry@aslws01.asl.dl.nec.com (Terry Bollinger) writes:
)Hi folks,
)

)It also makes it a lot easier to explain why large objects don't behave
)much like quantum objects.  The disproportionate impact of even a single
)photon on objects of largish size makes in nigh on to impossible to
)create an information vacuum that is sufficient to permit identifiable
)quantum behavior in such objects.
)
)Incidentally, once you start down this line of reasoning there is an
)unavoidable consequence: it de-mystifies Schroedinger's Cat, at least
)in a hand-wavy, ignore-the-operators sense.  Because the cat is not in
)an information vacuum, no significant superposition of states CAN
)occur -- the cat either lives or dies, PERIOD.  His life or death is
)recorded not in the mind of some observer, but in the enormous number
)of trace-leaving disturbances he makes to the box, air, and light all
)around him.  The fact that such traces would for the most part be very
)difficult to interpret in terms of life or death of the cat is not the
)issue -- the *potential* to recover information is all that is needed.

That's a very interesting way of looking at things, I'll agree.

Your arguments about information remind me of an argument I read a while
back, but haven't seen on the net.  I am not sure I can do it justice,
though.  And I've misplaced the reference (it was a semi-popular type
book though, not rigorous or quantitative) and I don't recall it's title,
either!

The basic idea was to pin down the idea of a 'Quantum measurement' a bit
more, to get a little bit better handle on the 'quanutm measurement' problem.
The idea was to claim that a 'measurement' "really" happened when
entropy increased - when something 'irreversible' happend.  This relates
pretty directly to your idea of 'information'.  (Of course, there's people
here who don't think in these terms at all.  I must admit that the idea,
relatively new to me (here from the net)  of sidestepping the measurement
problem has a lot of merit, but I suppose we'd digress into yet another MWI
debate :-).)

However, the vague part was that since small scale events are reversible, and
large scale events are not, it wasn't clear just what *did* constitute
entorpy, or 'information'.  The book discussed this a fair amount - enough
for me toI realize that I didn't have a very firm grasp of the idea, and to
get an impression that maybe there was some fundamental reason no really
sharp line could be drawn between 'reversible' and 'irreversible' processes.

)In such a perspective the apparent continued existence of the cat in a
)superimposed state would become more an artifact of the way the problem
)was analyzed than an expression of what actually happened.  The constant
)banging of the cat into the photons and atoms all around it would alter
)and deposit changes (information) in such a fashion that *each* such
)event would need to be considered an "observation" that closes down some
)component of the wavefunction.  The cat simply never has an opportunity
)to become quantum, because it is too huge to escape this kind of subtle,
)non-human "observation."
)
)COULD THE QM KITTY EVER EXIST?
)
)Could you recreate Schroedinger's scenario in the same way as the bullet,
)by placing him in an information vacuum (vs. the usual extremely leaky
)box)?  I doubt it.  In the QM bullet the superposition was in terms of
)the relation of the bullet to the universe from which it was isolated.
)In the case of the kitty the issue of life or death is internal to the
)cat, where no such information vacuum exists.  All you would gain by
)placing the poor critter in an information vacuum is the possibility of
)some QM interference with regards to where he lands -- not whether he's
)dead or alive when he gets there.
)
)By such a definition *no* living system could ever enter into any really
)significant superimposed state, because a living system simply does not
)provide any real potential for the development of information barriers.
)Everything is a bit too touchy-feely from cell to cell to let things
)drift very far into significant quantum uncertainty.

Yep.  That's the argument the unamed source I mentioned used too.  They
argued that passing a particle through a calcite prisim didn't constitue
a 'measurement', becasue you could 're-hide' all the information (to use
your terms) by recombining the particle by passing it through an identical
prism to recombine the spatially separated wave functions functions.
You could, so to speak 'unmeasure' it, put things back the way they were.  At
some point, some possibly fuzzy point, it becomes impossible to do this
anymore according to the 'laws' of thermodynamics, howver.  This was the
proposed answer to the 'problem of measurement'.

There were some arguments about whether a photon hitting a phosphor screen
constituted a 'measurement' in this sense too, but I don't recall the details
anymore, except that I was surprised to hear that some people felt this
could in principle be 'reversed' and the photon 'unmeasured' / (i.e. the 
information hid), but I didn't have any idea why they felt this might be
possible.
Newsgroups: sci.physics