Re: Has FTL communication really never been tested in this way?

Andreas Most:
You cannot remove the coincidence unit.
This has nothing to do about whether you have
a "clean source" of entangled photons.
The measurement on the idler so-to-say
selects the valid pairs. There is no way
to settle this in advance.

If you want to measure the two-photon interference,
you have to observe, and register, the behaviour
of both entangled photons, the idler photon at its
wing, the signal photon at its wing.

This has much to do with Wheeler's (and Bohr's) saying:
'No elementary phenomenon is a phenomenon until it is
a registered phenomenon.'

Of course, because we are performing a two-photon
interference experiment, we must use an appropriate
source of entangled photons (this source must have
a 'large' size).

Now we can also ask something like this.

Imagine we want to observe what happens at the signal
photon wing only. That is to say: we want to see if there
is some visible interference pattern, made by signal
photons, on the two-slit interferometer screen,
without looking at the other side (where somebody
else is measuring the idler photons).

(We do not use the coincidence detection unit here,
because we are interested in whether there is some
visible interference pattern, made by signal photons,
on the two-slit interferometer screen, without looking
at the other side, where idler photons are measured).

And imagine we cannot see any interference pattern
on that screen. (Apparently this is very strange
because we have a two-slit interferometer and a beam
of photons, and we do not see any interference
pattern).

What is the reason?

The possible reason seems (to me) this one. Signal
photons cannot cause their interference pattern on
the screen because their momentum uncertainty is large.
And their momentum uncertainty is large because the
source of entangled photons we (must) use to perform
a two-photon interference experiments has a 'large'
size (divergence of the beam).



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