Quetzalcoatl's Cat

[Quetzalcoatl]

I understand (I hope I got this right, otherwise the rest of this post is a big waste of time) that in a regular double-slit experiment, if i have a detector turned on at the slits, but nobody ever sees the detector's results,

one would see an interference pattern on the screen.

 

Now, me and my cat are both physics buffs. We went out to do some experimenting in our QM lab. So me and my cat agreed (under oath!) that the cat would peek at the detector results, but would never tell me what they were.

As for me, I just sat down next to the screen, waiting for some pattern to show up.

 

1. What would I expect to see? An interference pattern or not?

 

Repeat this with a robot instead of a cat (w/o memory).

2. What would I see then?

 

3. Essentially, what does it take to be an observer so that the observation "collapses" the wave function observed?

 

If I'm way off, please tell me... B)

 

PS: No animals were harmed in the making of this post.

[Sisyphus]

I understand (I hope I got this right, otherwise the rest of this post is a big waste of time) that in a regular double-slit experiment, if i have a detector turned on at the slits, but nobody ever sees the detector's results,

one would see an interference pattern on the screen.

 

It doesn't matter whether anyone sees the results. What matters is whether the physical layout forces the photon or whatever to go through one slit or the other. A detector alone would accomplish this.

[IM Egdall]

Here is the simple but strange quantum rule.

 

In the double-slit experiment (and others like it):

 

If you can,

in principle

, detect which path the photon takes, then there is no interference

 

If you cannot,

in principle

, detect which path the photon takes, them there is interference.

 

This rule applies not only to photons, but to all particles. And every experiment conducted to date has confirmed this law of nature.

 

I found the following simulation a real help in visualizing what happens:

 

http://phet.colorado.edu/en/simulation/quantum-wave-interference

 

[Quetzalcoatl]

So that means that if the information about the path exists in the universe in some form (e.g. state of the detector affected by the measurement) then there is no interference pattern. thank u both!