[extropy-chat] Re: Damien grants psi evidence

[Hal Finney]

Dirk Bruere writes:
> An interferometer with (say) a 4uS transit time (eg monomode fibre in 
> Sagnac configuration). We also have a random number generator based upon 
> (say) a radioactive decay providing a single quantum event clocking a 0 
> or 1 from a high speed counter.
> Over a period of time the count should be fairly predictable 
> statistically and evenly distributed between 0,1.
> However, what we do is to trigger a measurement on the interferometer 
> within 4uS of getting an output from the random number generator of a 1.
> If the 're-run' is affecting the universe as a whole the result will be 
> that the output of the RNG is skewed towards 0.
> Any comments and statements of impossibilities are welcome (as long as 
> they are accompanied by an explanation).

See http://spiff.rit.edu/classes/phys314/lectures/dual4/dual4.html
for a description of a delayed choice expt of the type I think you mean.

The way I think of these is that the photon takes both paths.  If both
arms stay open, then the photon parts re-combine at the final beam
splitter and we get interference.  The output may go to only one of the
detectors.  If one arm gets blocked, that in effect performs a measurement
when the photon gets to that point.  At that point there is the effect
of wave function collapse, and the photon gets localized to one of the
two arms, at random.  If in the blocked arm, the photon is absorbed.
If in the other arm, the photon proceeds to the beam splitter and goes
randomly to one of the two detectors.

There's no real "delayed choice" from this perspective.  You choose
to open or close the arm before the photon gets to the blocker.
You certainly can't make the choice after the photon has passed through!
That would be true backwards in time causality.

Proponents of a delayed choice interpretation suggest that the photon
somehow has to decide whether it will be a particle or a wave at the
time it enters the apparatus, before the choice to block or not is made.
But really, that is a pretty absurd notion, that photons decide in
this way.

Hal