Organization: Penn State University
Date: Sat, 25 Jul 1992 15:28:24 EDT
From: <MRG3@psuvm.psu.edu>
Newsgroups: sci.physics
Subject: Re: ***********MIND-BLOWING GEDANKENEXPERIMENT**********
 <92206.164128MRG3@psuvm.psu.edu> <2387@nic.cerf.net>

Sarfatti says, in response to some unseen note from Carlton Caves
(which I would like to see posted):
  (begin quote)
(Stuff indicating that Sarfatti does not really understand implications
 of linearity, probability, and independent evolution in QM deleted).

                                     ... Are they saying that half-wave
plates behave differently for pair correlated light than for uncorrelated
light? That would be an interesting phenomenon it true.
Given [|v1>|v2> + |h1>|h2>]/sqrt2 , if by local unitary evolution the
phase plate sends |v2> -> e^iphi|v2> and the have wave plate sends
|h2> -> |v2> (half wave plates rotate plane of linear polarization by
90 degrees says every optics text book) And I am using exactly the same
method that Wooters and Zurek used to prove that you cannot clone a photon
for arbitrary linear polarization in a laser amplifier which disproved Nick
Herberts FLASH FTL communicator - then evidently by the linearity, unitarity
and superposition principles and by elementary algebra of the distributive
law for kets
The initial entangled state [v1>|v2> + |h1>|h2>]/sqrt2 ->
[|v1> + e^iphi|h1>]|v2>/sqrt2 probability is conserved! p(v1,v2) = 1/2 and
p(h1,v2) = 1/2 { p(v1,h2) = 0, p(h1,h2) = 0, p(v1) = 1/2, p(h1) = 1/2,
p(v2) = 1, p(h2) = 0} so what is this garbage that probability is not
conserved. What false nonsense. What is this garbage that |v2> + |h2>
or |v1> - |h2> have any relevance to the problem whatsoever? Is every
one crazy? (I do not mean everyone I just mean academics in physics
departments - and only a subset of them at that.). I rest my case.
PLEASE PUT THIS ON INTERNET SO THAT THE WORLD CAN JUDGE. Someone out there
must be able to be rational about this. I am quite ready to accept that
I have made some sort of mistake - but the "spin-flip mystery" argument
is total nonsense as far as I can see.
 (end quote)

As Sarfatti describes the spin flip process, the transition is given
as a local transition involving system 2 only:
|v2> -> phase times |v2>
|h2> -> |v2>
Sarfatti admits that the superpostion principle should apply, and that
this transition should not depend upon the entanglement of the two systems.
And yet he seems confused when Caves apparantly demonstrates that this is
not in general probability conserving when other (single particle)
states are applied to the spin-flip!!!
If the Sarfatti spin-flip operates on single photons, then we should certainly
be able to  talk about what it would do in another apparatus, where states
like |v2>+|h2> and |h2>-|v2> appear.  Unless of course the Sarfatti
spin-flip device depends (nonlocally, aha!) on the rest of the apparatus.
Physics academia is not crazy.  However, it sounds like Sarfatti is a little
rusty in his quantum mechanics.  From the references to Caves communications,
I believe that he demonstrated quite clearly that the Sarfatti spin-flip
is not standard quantum mechanics, using only linearity
and the superpostion principle.  As a last resort, if Sarfatti insists
that there be two systems, I ask him to consider replacing the original
source which emits (normalization)x(any system 1 state)x(|v2>+|h2>)
or                       "                 "           x(|v2>-|h2>)
or generally             "                 "           (any system 2 state)
Is probability conserved in general?  (It won't be)  Is this
QM as usually used?  (not if it failed above)  But don't take my word for
it, so some calculations, instead of declaring concrete counter arguments
to be utter nonesense)

The bottom line: the superpostion principle means that a given form of
evolution must be probability conserving for ALL initial conditions.
It may be that Sarfatti has fooled himself because the Sarfatti spin-flip
conserves probability for his one particular initial state.

-An aside.  If one takes the indicated 2 system transitions
|h1>|h2> -> |h1>|v2>
|v1>|v2> ->phasex(v1>|v2>)
and explititly constructs the transition matrix, knowing only that evolution
must be unitary, one will find that the the transition is inherently nonlocal
in that it depends upon both system 1 and system 2.  It is then the nonlocal
nature of the Sarfatti spin-flip which allows FTL communication.

There are a number of very general no communication theorems for standard
QM.  (my favorite is one by Ghirardi, and (I forget, the reference is not
handy))  Sarfatti should take a close look at these no signaling proofs
and explain why they do not apply to his model.  Any FTL communication
proponent should be forced to clearly indicate the specific loopholes
they have found, not neccessarily in all such proofs, but in at least one.
So I ask Dr. Sarfatti, what is your favorite no signal proof, and where
(which premis) does it break down?
-mike gallis

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