Re: Shahriar S. Afshar Quantum Rebel (2)

From: Hal Finney <hal.domain.name.hidden>
Date: Mon, 26 Jul 2004 10:28:12 -0700 (PDT)

We discussed Afshar's experiment before. Kathryn Cramer, the blogger,
is John Cramer's daughter. John Cramer invented the Transactional
Interpretation of QM, similar in flavor to Bohm's pilot wave theory,
and his daughter is pushing Afshar's results as being best understood
in the context of the TI. Actually she goes further and claims that
Afshar falsifies both the Many-World and the Copenhagen Interpretations.

The CI is not falsifiable IMO because it is too vague and amounts
to little more than a policy of not asking embarrassing questions.
Physicists can get their work done and leave philosophizing to others.

The problem the Transactional Intepretation has with the MWI is that
worlds in the MWI never fully disengage. There is always an exponentially
decreasing connection between them. This means that the quantum formalism
would reflect the actions of intelligent beings in shadow worlds who are
different from ourselves, if we calculated to enough precision.

This is true even in the TI or in Bohm's theory. Those theories may
deny the reality of other worlds, but in principle they have to take
into consideration what would be happening there in order to make
their calculations. This is obvious in a double slit experiment,
but the phenomenon never goes away completely, no matter how far we go
towards decoherence.

Let Schrodinger's cat become alive or dead, but suppose there is some
super-advanced technology that can reverse the process of death at the
quantum level, undo the decoherence and restore a coherent state. Now,
even the TI has to take into consideration the actions of those in the
other world who performed that technological miracle.

This may seem too far-fetched even to consider, but we are taking tiny
steps today in this direction, pushing farther into the decoherence
frontier. So far everything suggests that QM holds up, meaning that
interference is still detectable with proper experimental setup even
after substantial amounts of decoherence. All the MWI says is that this
effect, which is exactly what is predicted by standard QM, will persist
even as decoherence advances so far that we can no longer measure the
interference.

Either an interpretation has to accept the reality of parallel worlds,
making it a version of the MWI; or predict that this effect will no longer
occur, which will violate QM; or deny that the people in the shadow worlds
are real, even though the ripples of their actions affect our own world;
or it has to stick its head in the sand and deny that it matters since
we can't detect those ripples anyway today, and probably will never be
able to do so. I'd be curious to know which choice the Transactional
Interpretation makes.

Hal Finney
Received on Mon Jul 26 2004 - 14:16:53 PDT