From: scerir (scerir@libero.it)
Date: Wed Jan 22 2003 - 09:00:57 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.
[part II]
We have seen that, according to Von Weizsaecker
(and, of course, Bohr) complementarity between
many kinds of localization and superposition is
a general feature of QM.
Some interest arises, these days, about a new
interpretation, to be called - I suppose - MTI,
many times interpretation. Let us have an atom,
in some excited state. In such case the energy of
the atom is indeterminate, the atomic state being
in a linear *superposition* (with appropriate amplitudes)
of all possible states that can be reached by the
particular excitation. Now the rate of spontaneous
emission from the excited atom (better say here: from
an ensemble of equally excited atoms) oscillate
*in time*. This time-like interference is caused
by the probability for the emission to occur at
time t (with emission of a quantum). Actually this
probability has an interference term, because we do
not know from *which*, of all possible atomic states,
the emission is caused.
Having here a sort of superposition in time (and not
in space) the quantum Lotto ... might be useful. (Do
they patent also these non-senses?)
Bohr and Heisenberg had many 'turbulent' discussions
about uncertainty relations (Heis. principle). Are they
an implementation of the complementarity principle?
Now people think they are just that. And, maybe, we
will see it, later.
At that time Bohr and Heisenberg were in agreement
about this, at least. Any attempt at a *well* defined
subdivision within a quantum phenomenon (i.e. between
quantum system and apparatus)would require a change
in the experimental set-up such that the phenomenon
disappears. In Heisenberg terms this becomes: the right
place to find the uncertainty is the micro-macro
boundary.
So that (Damien's) 'impression' (that 'even in principle..')
was cute, as we'll see in the next post. And was right and
wrong at the *same* time. Heh, we are discussing QM,
are not we? :-)
In general the paradoxical (non local-realistic) features
of QM, in most interpretations (*), just show how QM is
trying to reach, at the very *same* time, maximum of uni-ty
and maximum of di-vers-ity. Somebody called that 'uni-verse'.
Somebody else maybe 'multi-verse'!
For a new demostration of the above see:
http://www.oberlin.edu/physics/dstyer/StrangeQM/Hardy.pdf
and the performed experiment at L. Berkeley Labs:
http://arxiv.org/abs/quant-ph/9908081
(*)
- In example the Copenhagen-Bohr (complementarity,
uncertainty, non-commutativity, our language cannot
reproduce quantum features, the role of the observer,
Born rule, etc). Note that, surprisingly enough, Bohr was a
'realist', and not a 'positivist'. And not a 'surrealist'
like Pauli. Bohr thought that Einstein's realism was too poor.
- Or the Gottingen-Heisenberg-Born (emphasis on matrix
mechanics, on Born rule, and, later, on potentiality).
- Or the Princeton-Von Neumann-Wigner (Von N. added the operator
representation, a model of measurements, the 'collapse'
(invented by Heisenberg), and, with Wigner, the 'psycho-
physical'parallelism, the 'consciousness', Wigner also added
many operators, his negative probability 'functions'...).
http://focus.aps.org/story/v8/st7
http://arxiv.org/abs/quant-ph/0101051
- Or the MWI-Everett-Wheeler-De Witt.
- Or the Dirac-Feynman representation (Lagrangians, actions,
paths). Note that actually Dirac did not even write the word
'wavefunction', never, as far as I know.
- Etc.
[part III coming, hopefully less boring than this one]
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