Re: [asa] Quantum physics, measurement problems, other implications?

Hi! Schwarzwald;

I can sympathize with the difficulty you encountered in trying to understand
QM. At least you had others who would discuss it with you, (although they
may in fact have made understanding QM more difficult) I have not until now
found anyone to talk to about it.

You have spoken several times of the double slit experiment. Young used a
light source and colored filter to provide monochromatic light. The light
was passed through a single slit, then a pair of slits whose width and
distance apart was critical, the light was then shown upon a screen. The
result was a double slit interference pattern. Young used the interference
patterns produced by water waves to explain the outcome and provided a
classical mathematic solution.

I understand that modern double slit experiments use a slightly different
set up. A monochromatic, variable intensity laser is used as the light
source and this shins on a pair of slits whose width and spacing are
critical. The light is then shown upon a CCD or other suitable detector.

A. If the laser is turned on in the usual way the outcome is a double slit
interference pattern, as was seen in Young's experiment.

B. If the intensity of the laser is diminished so that only one photon
enters the system at a time, the outcome is still a double slit interference
pattern. I think Young as a classical physicist would have been surprised by
this outcome.

C. If one of the slits is blocked, no interference pattern is formed.

D. If an active detector is placed behind one of the slits, no interference
pattern is formed.
Once he understood that an active detector distroys the photon, I don't
think Young would be surprised by the C or D outcomes.

Does this accurately describe the setup and results of a modern double slit
experiment? Are you familiar with a double slit experiment in which a narrow
screen perpendicular to and in the middle of the double slits is used? How
about one in which both slits are kept open but the light source is directed
so that the light can pass through only one slit?

Will you comment please on the results of the modern double slit experiment?
Also would you be so kind as to describe the setup, results and
interpretation of the delayed choice and quantum eraser experiments.

Thanks, Michael McCray

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Received on Mon Nov 24 18:16:34 2008