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From: gwyn@brl-smoke.ARPA (Doug Gwyn )
Newsgroups: net.physics
Subject: Re: quantum mechanics and all that
Message-ID: <687@brl-smoke.ARPA>
Date: Wed, 5-Feb-86 19:19:03 EST
Article-I.D.: brl-smok.687
Posted: Wed Feb  5 19:19:03 1986
Date-Received: Sun, 9-Feb-86 04:50:20 EST
References: <10137@tardis.UUCP> <6746@boring.UUCP> <11661@ucbvax.BERKELEY.EDU>
Reply-To: gwyn@brl.ARPA
Distribution: net
Organization: Ballistic Research Lab
Lines: 24

>>> Assume I put a cat into a box, ...
...
>If there are two paths to exactly the same final state, you add their
>complex amplitudes (interference).  But if these paths really lead to
>two different final states, the probability of getting to either is
>the sum of the probabilities of each (no interference).

My opinion is that the one real mystery (non-intuitive fact)
of quantum theory is how the "probability amplitude" business
can be understood.  If one can really comprehend how the
"two-slit experiment" works on an internalized intuitive basis,
then Schr"odinger's cat and the other usual paradoxes would
be straightforward extensions of the same idea.  (EPR seems to
raise a different issue.)

I have never found a good explanation (as opposed to description)
of how the superposition of probability amplitudes work.  The
best arguments that I have heard amount to "it's self-consistent,
and it works", which I might agree with and still not think I
understand what's going on.  I will say that most people giving
such arguments have not shown that they understand probability
theory very well, so one wonders whether a satisfying explanation
might not be possible after all.  This issue is at the top of my
list of spare-time (ha!) projects.