[extropy-chat] beyond super-position

[scerir]

"It or Bit?" asked Wheeler, and Zeh, et al.
It seems that the Wien school (Zeilinger and coworkers)
follows both ways. "Bit" and now also "It"
http://physicsweb.org/article/news/8/2/9
in the sense that you can try to "explain" interferences
in abstract terms ("Bit", limited information)
http://www.arxiv.org/abs/quant-ph/0201026
and also in physical terms ("It", [de]coherence).

It seems interesting to say that concepts like
"Bit" and "It" are mixed up not just in the
space-like picture, but also in the time-like
picture, that is to say in the (so called) quantum
delayed choice (or retro-causation), formulated by 
von Weizsaecker (and also Einstein, if I remember well), 
and 50 years later by Wheeler.

As Anton Zeilinger writes (Rev. Mod. Phys., 1999, page S-288)
"The superposition of amplitudes is only valid if there
is no way to know, even in principle, which path the particle
took. It is important to realize that this does not imply
that an observer actually takes note of what happens.
It is sufficient to destroy the interference pattern,
if the path information is accessible in principle from
the experiment or even if it is dispersed in the environment
and beyond any technical possibility to be recovered, but
in principle 'still out there'".

"In an experiment the state reflects not what is actually
known about the system, but rather what is knowable, in principle,
with the help of auxiliary measurements that do not disturb
the original experiment. By focusing on what is knowable in
principle, and treating what is known as largely irrelevant,
one completely avoids the anthropomorphism and any reference
to consciousness that some physicists have tried to inject
into quantum mechanics" writes Leonard Mandel (Rev. Mod. Phys., 
1999, p. S-274).

Now, imagine that (i.e. in the two-slit apparatus) the information 
about the "which way", the "welcher weg" the the atom, or the C-70 
Fullerene took, is still out there, in the air (i.e. in the form of 
scattered photons), and imagine you can *still* read - or you can 
*still* erase - this information when the atom, or the C-70 Fullerene, 
has *already* reached the screen (or the detector array). It turns 
out that the pattern on that screen (interferential or not) depends 
on that *still* readable - or *still* erasable - information.
Retrocausation.