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Old May 16th 2017, 02:33 AM   #1
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Question Double slits experiment with one or two detectors

Does it matter if there is a detector in every of the two splits, or just in one of them? Will there be any difference?

I wonder if I asked the question correctly. I mean will the result of the experiment be different if we stick a detector only in one slit, and the other slit will be undetected.

Last edited by Fox333; May 16th 2017 at 10:15 AM. Reason: adding information
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Old May 16th 2017, 01:21 PM   #2
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A detector at either slit seems to enough to destroy the interference pattern
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Old May 16th 2017, 11:33 PM   #3
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This video with english subtitles should help

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Old May 16th 2017, 11:57 PM   #4
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Thanks. The other question: let's say there is a detector in the left slit. Is there 50/50 % probability to detect the particle in the left split? So, 50% of experiments will end with detecting the particle in the left slit, and 50% with detecting nothing, but without observing the interference pattern?
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Old May 17th 2017, 03:22 AM   #5
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My understanding is a detector on either side will destroy the interference pattern as shown in the above animation clip. I assume that particles go through each slit with equal probability or 50/50.
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Old May 17th 2017, 04:20 AM   #6
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There could be two possibilities:
1) assuming the "ordinary" logic: having a detector in the left slit, we will observe the particle in the half of cases. In the other half the particle will leave undetected. We can only assume that it leaves throw the right slit. No interference pattern.
2) alternative possibility: we will always detect the particle in the only left detector. No interference pattern, but we can detect the particle in the 100% of cases.
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Old May 17th 2017, 10:47 AM   #7
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Some of you will probably disagree...

I personally favour an interpretation that leans toward the De-Broglie Bohm pilot wave theory (rather than the Copenhagen Interpretation).

My interpretation is that every particle contributes to a probability field, within which the probability of a particle existing at a given position (and time) is dependent on the relative situations of all the other particles around it.

In order to produce the double slit effect one has to quite carefully arrange things such that the probability field the particle traverses allows for two essentially equally probable paths.

It is impossible to introduce a detector (no matter how subtle) and maintain that finely balanced probability field.
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Old May 17th 2017, 11:16 AM   #8
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Woody, I see, indeed, it's one of possible interpretations.

Personally, I'm interested more about the real experiment and its outcome. I mean the double slit experiment with only one detector: have it ever been done? If yes, was the particle detected in 50 or 100 % cases?
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Old May 17th 2017, 11:39 AM   #9
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There is an animation of the experiment with one detector on minute 9 of the video, was there a real experiment like that?

If it was really like that, so there is a question: why the pattern disappears if the particle wasn't detected? We can't know that it passed from the other slit, we can only assume that. We don't have any observed fact, we only have an assumption. But it breaks the pattern anyway. Why?
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Old May 17th 2017, 02:46 PM   #10
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Originally Posted by Fox333 View Post
There could be two possibilities:
1) assuming the "ordinary" logic: having a detector in the left slit, we will observe the particle in the half of cases. In the other half the particle will leave undetected. We can only assume that it leaves throw the right slit. No interference pattern.
2) alternative possibility: we will always detect the particle in the only left detector. No interference pattern, but we can detect the particle in the 100% of cases.
I don't think #2 is correct. We would still see two bands on the screen indicating that the particle at various times went through either slit. However, we only detected it in the left.
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