Notes on
Hardy’s Ladder experiment
(Caroline H Thompson, 28:10:97
and later)
28:10:97.
Some
crazy and irrelevant logic, misapplied to an interesting experiment.
Uses two
horizontally polarised photons, equal frequency, from PDC of ultraviolet
light. Pass through various Fresnel
rhomb polarisation rotators, Glan-Taylor beam splitters and calcite crystals. My interpretation: Result seems to show that
coincidences only have interesting pattern when interference is
constructive/destructive, controlled by phase differences.
From correspondence with “Dan M” (in sci.physics
newsgroup?):
It's
horribly difficult to see what he is doing, but I think that the
fact that
he has alpha and beta unequal (ratios vary from 0.46 to 0.64)
means that
in any one run the signals are mostly vertical or mostly
horizontal.
We ought to
ask Hardy what his singles rates did, as I would suspect that
they would
have varied with absolute values of theta.
This is not like
the proper
Bell setup. No pretence of rotational
invariance, so it is
not
difference in angles that matters. If
his singles rates did not vary
very much,
that could be because the subset that takes part in the
coincidences
is just a small one. To form a
coincidence you need to be
almost
exactly in phase with your partner, I think. I think it is just
phase
difference that is our "hidden variable", completely random between
the two
emissions from the crystal.