[extropy-chat] Cramer on Afshar

scerir scerir at libero.it
Sat Nov 13 14:11:43 UTC 2004


> Does Afshar agree that his V<<1 only as you suggest?
> Walter.

Well, S.Afshar is brilliant. But it is difficult
to develope a consistent ontology wich is simpler
and stronger than the orthodox QM, wich - in general -
is based on observ-ables (correlations, operations,
contexts) and not on be-ables (entities, correlata,
hidden variables, etc.). 

(I wrote 'in general' because there are cases, 
and measurements, in which observ-ables and be-ables 
are the same thing, or, to say it in another way, 
pre-dictions or retro-dictions are possible, i.e.
http://prola.aps.org/abstract/PRA/v42/i9/p5720_1
http://physmag.h1.ru/bibliography/1_4.html )

So S.Afshar writes: "Am I right in saying that according 
to your view, there is negligible flux on the wires? If yes:
1) Then we have no choice but to declare that the cause 
of this lack of incident flux is destructive interference. 
There simply is no other process by which a certain regions 
of space (wires) do not receive flux, while we KNOW that 
regions close to the wires do (we see all the photons 
at the image plane). 2) If you dont agree with (1), 
then please tell me how you can use QM to show a particular 
region CONTINUALLY receives no flux, without assuming
interference as the cause."

Now the problem here is a typical problem by 'lawyers'.
*Assuming* that interference is the cause of that
negligible flux at the wires, before the 'welcher weg'
ray optics apparatus, and assuming that there is 
an interference at the wires is not equivalent to
*showing* interference fringes at the wires.
Because in that expression V^2 + K^2 >/=1
the letter "V" is a *physical* measurement of visibility
of fringes (math expression avoided here) and it
is not a *meta-physical* assumption about the
presence of interference fringes. So V << 1.

In other words - as A.Zeilinger states it - a single
quantum can just carry the information about its nature
(particle-like, wave-like). But a single quantum carries 
a single bit of information. You can read this single 
bit of information just once. Not two times. Thus you can
reveal the 'sharp' particle-like or the 'sharp' wave-like
nature. Not both. (You can just reveal both natures 
at another epi-ontic level, the level of probabilistic 
knowledge. In this case you say that a single quantum
is 40% 'particle' and 60% 'wave', as Wootters and Zurek
showed in 1979).

That said, imo, there is little doubt that there is
an interference (let us say a "virtual" one)
at those little wires. But this is a deduction, an
inference, not a measurement.

One of the reason why is difficult to kill Bohrian
complementarity (different from the old duality of
light, different from the Heisenberg-Jordan duality 
of light which is based on the dual *formalism*) is
that there are many different complementarities.

There is the classical wave/particle smooth
complementarity (Walter, yes like the Yin-Yang).
The more you reveal one, the less the other.
http://www.upscale.utoronto.ca/GeneralInterest/

There is a "circular" complemetarity by von
Weizsaecker: between superposition of states and
localization of the "entity".

There is a Copenhagenist complemetarity: you cannot
reveal both natures of the "entity" using just one
set-up. You need a set-up for one nature, and a different
one for the other nature.

There is a complementarity between reversibility
and irreversibility (collapse).

There is a complementarity between continuity and
discontinuity.

There is a complementarity between separability and
unitarity.

There is a complementarity between distinguishability
and non-distinguishability of paths.

There is a complementarity "in time", meaning that
a single quantum (a single photon) can interfere
with itself "in time", provided you create two
different paths, one shorter "in time" and one longer
"in time", and provided the difference "in time"
between these two paths is shorter than the uncertainty
of arrival time of the single photon at the screen.
(This case is similar to the case of a single photon
emitted by two different sources - coherent or not -
so that you cannot know which source emitted the photon,
and you can combine the amplitude related to one source
with the amplitude related to the other source, getting
the experimental interference).

There is the strongest kind of Bohrian complentarity 
saying that you cannot follow the (causal) course of a
quantum through space-time. This is the most interesting
one. "... we are presented with a choice of either tracing 
the path of the particle, or observing interference effects" 
writes N.Bohr in 'Albert Einstein: Philosopher-Scientist', 
P. A. Schlipp Ed. (Library of Living Philosophers, Evanston, 
Illinois, 1949). It is the most interesting one because
it is possible to argue that there is no "causal" course
at all, since there is no time "in there", the only causal
link being *our own* clock time, *our own* causal mind.

s.

"The important conclusion is that, while individual
events just happen, their physical interpretation 
in terms of wave or particle might depend on the
future; it might particularly depend on decisions 
we might make in the future concerning the measurement
performed at some distant spacetime location in the
future."
- Anton Zeilinger

   





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