Re: Proof that macintosh is better than VMS

On Mar 16, 9:44 am, AEF <spamsink2...@xxxxxxxxx> wrote:

[...]

Sorry to follow up on my own post, but I forgot to give credit to
Feynman for the explanation of why you cannot even in principle
predict which path the photon will take even if the LCD is ON. All I
did was adapt it from the 2-slit experiment to this one (which is very
similar). I include the introductory remarks and the diagram only for
completeness.


Here's an excellent example to drive the point home. I saw a talk
about this in graduate school in the late 1980's. Consider the
following experimental set up:

F A B

[-LASER-]-----|-------\-----------------\
| |
| |
| - LCD
| |
| |
\-----------------\

C D

[...]

[Beginning of argument due to Feynman in Chapter 6 of The Character of
Physical Law adapted from the 2-slit experiment to the one illustrated
above:]

Now the question becomes: can you predict which path the photon will
take after passing through the beam splitter A with the LCD ON? Hidden
variable theory says you could do this by observing something at or
upstream of A. But if you could do that, then it makes no difference
whether the LCD is ON or OFF. Anything you observe with the LCD ON you
can observe with it OFF, and at the time of this observation, the
state of the LCD when the photon gets to it is still unknown. And if
you can successfully predict which path the photon will take, you
can't ever get the interference pattern with the LCD OFF, because an
interference pattern cannot be produced by photons traveling along a
single path, and an interference pattern is completely different from
what you would see if photons only traversed one path or the other.

[I added the following and a few, small snippets in the part above
relevant chiefly to this experiment.]

And there can't be any "secret communication" between the LCD and the
source or beam splitter at A because you can change the state of the
LCD AFTER the photon has passed through beam splitter A.

[Back to Feynman's argument:]

Therefore,
even with the LCD ON, there is no way to predict ahead of time which
path the photon will take if the apparatus is set up in such a way
that it can produce interference patterns with the LCD off.

[End of adaptation of Feynman's argument. Below is a reference to the
original.]

Please see
Feynman's Chapter 6 of The Character of Physical Law (from which this
explanation is borrowed) for the full story (well it's the full story
at the layman's level -- if you know about how the wavelength of light
affects resolution, and are comfortable with the de Broglie relation,
you can go a little deeper, but the essential points are covered by
the layman's version -- for the deeper version, see Feynman's Lectures
on Physics. Also, Feynman's explanation is most likely clearer than
mine!).

[...]

AEF
.

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