[extropy-chat] HISTORY: Solved & Unsolved Riddles

[scerir]

[In general the "entity" can be seen
as a carrier of information ...]

John K Clark (long ago, I'm late and sorry):
I don't see how it can carry information
if you can never detect it. We can never
detect the "entity" directly because it
isn't even a probability [...]


Difficult to answer to that. Of course some of
that information is visible, there are observables,
and there are experiments and procedures.
The rest remains hidden, because of QM formalism,
because of many evident Goedelian issues of a
theory which is not 'closed', because there are
operators which do not commute, because time
is not an operator, because QM seems sometimes
to be a-temporal, like in EPR effects, etc.
The main factor is the QM formalism, as
Dirac himself pointed out few times.
In example Weinberg tried a non-linear
formalism (after all the 'collapse',
if physical, might be a non-linear
effect). The modification was very very
modest, quantitatively. But Gisin showed
that any non-linear formalism allows
superluminal effects and also superluminal
signals (or, if you like, that the
'no-cloning' theorem is wrong, and that
uncertainty relations do not work).
So ... nobody having the 'status' of
Bohr or Einstein .... the non-linear
formalism died prematurely. But many
still think that linearity (superposition)
is the weirdest thing here around.
Even the concept of quantum 'state'
appears very feeble (Filkenstein,
and in a strange paper, Thom long ago).
But, pushing to the extreme QM weirdness,
now pieces of an alternative formalism appear.
In example Aharonov's 'weak measurement'
theory, the two-state formalism and the ABL
rule. From another point of view it was pointed
out many times that Heisenberg-Robertson
uncertainty relations are poor and, in many
cases, useless or meaninless (especially the
dEdt>h, as pointed out by Wigner, Peres, etc,
but also the other one). Now we have new
uncertainty relations based on entropies
(informations) involved. If I remember well
Deutsch was the first who wrote these relations.
To close this endless 'soup' I must quote
somebody who asked "What is the joint
probability of finding the particle to go
through hole 1 [in a two-slit] and be 180°
out of phase with hole 2 (whatever that
could mean)?". Scully, Walther, and Schleich
(Physical Review, A-49, n.3, (1994), p.1562)
found that the observable distribution
(interference pattern) is everywhere positive
but that joint probability can be negative.
So Feynman's intuition (quotation above)
was right, negative probabilities are
possible. But, to date, unobservable,
like any other single-particle non-locality.
(What a negative probability means is
another, perhaps Goedelian, matter !).
Regards
s.