  Another Bell test "loophole" - imperfect rotational invariance - is explored,
and novel realist ideas on parametric down-conversion as used in recent
"quantum entanglement" experiments are presented. The usual quantum theory of
entangled systems assumes we have rotational invariance (RI), so that
coincidence rates depend on the difference only between detector settings, not
on the absolute values. Bell tests, as such, do not necessarily require RI, but
where it fails the presentation of results in the form of coincidence curves
can be grossly misleading. Even if the well-known detection loophole were
closed, the visibility of such curves would tell us nothing about the degree of
entanglement! The problem may be especially relevant to recent experiments
using "degenerate type II parametric down-conversion" sources. Logical analysis
of the results of many experiments suggests realist explanations involving some
new physics. The systems may be more nearly deterministic than quantum theory
implies. Whilst this may be to the advantage of those attempting to make use of
the so-called "Bell correlations" in computing, encryption, "teleportation"
etc., it does mean that the systems obey ordinary, not quantum, logic.
