From: daryl@oracorp.com (Daryl McCullough)
Subject: Re:  Simple observation about Quantum Kitty Cats
Organization: ORA Corporation
Date: Mon, 5 Oct 1992 17:18:17 GMT

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

>However, when you start talking about information *vacuums* -- that is,
>experiments in which the ability to extract information about some set
>of ongoing events has been eliminated or at least severely curtailed,
>the idea "information" appears to take on a more precise meaning.  A
>unit of information is somehow related (probably by a fairly simple
>equation) to a level of reduction in QM interference effects exhibited
>by various type and sizes of objects.  The more information is extracted
>from the component within the information vacuum, the more that object
>will behave in a classical fashion.

I agree with your point somewhat, but not entirely. To extract
information about an object is to make your state become correlated
with the state of the object. It is easy to show that such
correlations destroy interference effects. However, having destroyed
the interference does not return the world to classical mechanics;
things can still be in superpositions of macroscopically different
states.

>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.

I disagree. The effect of multiple records of the cat's state is to
make the state of the rest of the universe correlated with the cat's
state. Let |dead> be the state of the cat when it is dead, |alive> be
the state of the cat when it is alive, |DEAD> the state of the rest of
the universe when the cat is dead, |ALIVE> the state of the rest of
the universe when the cat is alive, and |?> the state of the rest of
the universe when there is no information available as to the state of
the cat. Your point would seem to be that the situation rapidly changes
from being described by the state

     (|alive> + |dead>) x |?>

to being described by the state

     (|alive> x |ALIVE>) + (|dead> x |DEAD>)

There is still a superposition, but it doesn't only involve the state
of the cat. Furthermore, you say that "the cat either lives or dies,
PERIOD." As I pointed out in another article, this conclusion doesn't
follow from the mathematics of quantum mechanics. The reason for this
is that the total state of the world described above can just as easily
be written as

     1/2 (|alive> + |dead>) x (|ALIVE> + |DEAD>) +
     1/2 (|alive> - |dead>) x (|ALIVE> - |DEAD>)

What makes the states |alive> and |dead> a better or more accurate way
to describe things than |alive> +/- |dead>? The formalism of quantum
mechanics doesn't give an answer. It's possible that a preferred basis
is derivable from statistical mechanics (since such preferred bases
only come in with macroscopic measurements), but I have never seen it
done.

Daryl McCullough
ORA Corp.
Ithaca, NY

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