From: scerir (scerir@libero.it)
Date: Tue Jan 21 2003 - 08:11:57 MST
Damien
> That's one of the points I remain unclear about.
> [...]
> But I was under the impression that experiments
> (either real or gedanken) by Chiao and colleagues
> had shown that even *in principle* slit closure
> was enough to block interference.
The impression is correct. And I over-simplified,
in a previous post. I was inaccurate.
The 'complementarity principle', in a very good formulation
(by Von Weizsaecker, 1955), states that 'localization'
(of a quantum object) and 'superposition' are 'complementary'.
By 'localization' Von W. meant spatial localization, or
temporal localization (as time arrival, there is no
quantum time), or, in general, any sharp or
semi-sharp determination of the value of any other
quantum observable. (Hence we can have many kinds
of interference, and the time arrivals interference
is, at least, as interesting as the spatial interference).
The first question: is complementarity 'smooth'
or 'hard'? That is to say: does the interference
pattern change 'continuously' or not, when we try
to 'localize' an observable? This is an interesting
subject because many important authors (Wootters,
Zurek, Greenberger, Yasin, Englert, Ghose, Mittelstaedt,
and, in his 'informational' way, perhaps also Zeilinger,
etc.) suggested an *ontological* interpretation.
The *ontological* interpretation states that the wave-like
and the particle-like behaviour of a (single) particle,
are just the *extreme* forms of the *same* ontological
entity, the *particle-wave*.
Note that the *ontological* interpretation does not
agree with Feynman's philosophy.
'I want to emphasize that light comes in this
form - particles. It is very important to know that
light behaves like particles, especially for those
of you who have gone to school, where you were probably
told something about light behaving like waves.
I'm telling you the way it does behave - like particles.'
wrote Richard Feynman in 'QED' (1986, p.15).
Note that the *ontological* interpretation does not
agree with Bohr's philosophy, which says that complementarity
is a yes-no alternative, or an exclusive experimental
disjunction of 'both' aspects.
It is not easy, imo, to combine this *ontological*
interpretation (and any other realistic interpretation,
like the old one which says that a real 'wave' exists,
but does not carry energy or momentum) with the MWI.
[part II coming, as soon as possible]
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