From:
Caroline H Thompson [ch.thompson1@virgin.net]
Sent: 21
November 2004 17:50
To:
letters@newscientist.com
Subject:
Spooky spin?
The Editor
New
Scientist
Dear Sir
Though Ralph
Estling is absolutely correct (20 November, p 28) that if quantum theory is
right about "entanglement" of separated particles then we are
compelled to abandon either "naive reality" or "locality",
as far as actual experimental evidence is concerned he has no need to worry. There has never yet been a "Bell test
experiment" (one designed to test quantum theory against local
realism)that has been free of "loopholes". In consequence, it is
possible to find alternative explanations using the tried and tested methods of
conventional science, with nothing more alarming than the kind of effect Bob
Millar (30 October, p30) described, which amounts to "Estling's
Partitioned Trousers": the two particles share parameters set at the
source so that when we measure one we automatically know the value of the
other.
This being
the case, how does it come about that so many people -- experts and amateurs
alike -- believe that quantum entanglement has been proven? This, for me, is the big mystery! Could it be that it has something to do with
belief in the photon model of light, since it is hard if not impossible to find
a plausible explanation for the results of optical Bell tests unless a wave
model is adopted? Or perhaps it is
something more general than this: a conviction that the *whole* of the rest of
quantum theory has been completely confirmed?
But if that is the case, why do the experiments at all? They were supposed to stand on their own
feet, and the fact of the matter is that they have not so far been able to
discriminate between the two alternative explanations. The search for a "loophole-free"
test is being pursued with vigour by, among others, Philippe Grangier, who was
a member of the original team working with Alain Aspect in his famous
experiments of 1981-2. His latest idea
can be found at http://arxiv.org/abs/quant-ph/0403191
.
For more on
the Bell test loopholes see http://en.wikipedia.org/wiki/BellTestLoopholes
and related pages, or my web site, http://freespace.virgin.net/ch.thompson1/
.
Yours
sincerely
Caroline
Caroline H
Thompson
mailto:ch.thompson1@virgin.net
http://freespace.virgin.net/ch.thompson1/