New quantum measurement paradox?

[Neil Bates <neil_delver@yahoo.com>]

   As far as is known, we can measure the polarization state (ie, linear
orientation or circular handness) of a photon only via crude yes-no
methods. Here I would like to present a concept for how to possibly
measure the amount of circular polarization of a single photon. I
appreciate the case against doing that, but - as per Maxwell's Demon and
other attempted end-runs against laws of physics - examination of the
argument can lead to insight into quantum measurement in any case.
Debate about the proposal should be interesting and fruitful.
   Imagine having a detector stack (DS) of n spaced half-wave plates
with an axle running through their centers. Now interleave between these
plates (covering up to reach near the axle) another set of n plates
connected to another framework, keeping the first stack's lower plate
bottom-most. If a right-hand photon enters the stacks properly from
below, its circular handness is flipped in alternation by each HW plate.
The photon goes from RH to LH to RH ... . That adds angular momentum to
successive HW plates according to the sequence: 2hbar( + - + - + ...).
Since the odd-sequence plates are connected on the same axle, the
accumulation of RH angular momentum will add up to a net value
transferred to the DS of 2n*hbar. We could detect this spin in principle
(as did R. Beth in 1936), but we'd need many, many plates for a single
photon.
   This does not seem extraordinary so far, but consider what should
happen if a linear or elliptically polarized photon crosses the DS.
According to quantum statistics, the chance of that photon manifesting
RH or LH is based on its degree of circular polarization. Hence, a
linear photon should randomly transfer RH spin 50% of the time and LH
spin 50% of the time to any HW plate it encounters. Thus, on average,
the spins transferred by such a photon to disks in the DS should cancel
out, and we would know that the photon was linear. (For photons from
elliptical-pol sources, the torque-moment should be proportional to
amount of circularity.) This indeed accomplishes more than thought
possible! I'll call the entire arrangement a photon circularity
spectrometer - PCS.
   Even more interesting, we could put a quarter-wave plate in front of
the stacks and change different linear polarization angles into magnitude
of circularity. Then the PCS could distinguish between linear photons of
different orientations. This would ostensibly allow us to take advantage
of the correlated linear polarizations of the EPR effect, and
communicate instantly across huge distances (as discussed by Nick
Herbert in _Faster Than Light: Superluminal Loopholes in Physics_.)
Since nature so far keeps us from doing such things (as per "cloning"
limitations, etc.,) such measurements are supposedly impossible - but the
argument sounds so reasonable. Even if the PCS wouldn't work, will
*something* have to be adjusted in our understanding?

Neil Bates

neil_delver@yahoo.com