Actually, if you read Zeilinger's article carefully, he explains why
he has not made an FTL system.
On page S291
"We note that the distribution of photons behind the
double slit without registration of the other photon is
just an incoherent sum of probabilities having passed
through either slit and, as shown in the experiment, no
interference pattern arises if one does not look at the
other photon."
This is what JB referred to when he said "Not true", and is what kills
the experiment I was thinking of in my previous post. The trick in
entangled measurements is always a "coincidence circuit", where
effectively A and B can talk to eachother and compare notes.
But this "talking to eachother" is always done "conventionally" at
slower than light speed!!! Note in Zeilinger's Figure 3 that the two
detectors have wires coming out of them going to the coincidence
logic. This is decidedly slower than light (at light speed at best),
and so the system as a whole is not FTL. Each on its own does not have
the interference pattern, but together they can have one.
You have to read very carefully!!!
As you are interested in this sort of thing, try and wrap your neurons
around another mad experiment
"A delayed choice quantum eraser"
http://arxiv.org/PS_cache/quant-ph/pdf/9903/9903047.pdf
where again, no interference pattern is observed until the other
entangled photon has its "which path" information destroyed. And
again, interference is *only* observed when D1 and D2 are compared to
eachother at a coincidence circuit (which is always slower than
light!).
BR
.
|
