After eq 14, you can recover the interference pattern by the following method, which is what they did. I guess you didn’t follow the experiment too closely.
Or is it the case that, for speed-of-light reasons, there can never be enough time to switch the polarizor OFF if the s-path photon indicated it was ON and vice versa?
If you make the p path long enough, I don’t see why not. A fiber optic loop should work. I know that’s been done before.
Interesting question, but since you know it’s been done before, what were the results?
Half Man Half Wit and others knowledgeable about QM:
If the fiber optic loop was so long it took 2 years for the particle to get to the polarized plate, and the polarization was switched 1.9 years after after S particle was detected, what would we observe prior to the polarization change?
Is the problem with this approach that our observation of the S particle result prior to the polarization change un-entangles S and P?
I thought it was obvious that what I meant was that fiber optic loops had been used as a means to extend the travel times of photons in experiments - not that this particular experiment had been done that way. Certainly if it had been, I would have shared that information, but I suppose I could have been more explicit.
If the result really is time independent, then it should agree with whatever position the p polarizer ends up in. If it doesn’t, then maybe the result has to do with spatial or temporal coherence. But I don’t really understand those concepts well enough to speculate.
I’m guessing, but I think the answer is as follows:
1 - If we wait 2 years to look at the S results then the experiment is identical to the OP
2 - If we look at S results prior to 1.9 years (when the polarized plate switches) then we have just altered the experiment by observing S causing the wave function collapse etc.
First off, it’s at +45 and -45 degrees, not 145 and 245 degrees.
Nice. Yes I did follow it. See my post 52 (again):
Anyway, I’m done talking to you.
In principle, you can perform the experiment in a low noise environment, so that all of the s photons detected are entangled with some p photon, even though you don’t know its polarization. (That is you don’t need the coincidence detection to determine if the photon is part of your experiment, versus some extraneous photon.) If you wait two years to measure the p photons, you have no way of separating the observed s photons during that time. So you only have the sum of all s photons detected, which shows no fringing. You can only separate them once you’ve brought the measurements of the p and s photons together. Then you can split the s photons into x+y and x-y photons, which will then give the fringing and antifringing patterns.
OMG, you never even bother to look at the original paper did you? I cut and pasted that from Adobe Acrobat and didn’t bother to check it. If you look at the original it says +45 and -45. When I did the cut and paste the plus and minus were corrupted.
LOL!!!
If you had actually looked at the original paper you would have known that.
I’m grateful for the fact that you won’t be speaking to me.
OK, so it sounds as if every time the s-path photon ends up in a position which would have higher probability if the p-path had polarizer ON, you can turn the p-path OFF, and vice versa, and thereby force this experiment to come out wrong. Am I misunderstanding something?
I’m not sure what you mean. If the quarter wave filters are in place and the p polarizer is in place, you should get the interference pattern. It’s not a matter of probabilities. If the p polarizer is not in place, the no pattern.
I’m not sure I understand you correctly, but if you look at the s detections at any time without taking into account the detections from the p-path detector, then you will not observe an interference pattern. Only if you bring both into coincidence can you observe the pattern.
The fact that each detector records each hit I’m pretty sure qualifies.
I’m not sure why you can’t understand my question. Whether the p-polarizer is or isn’t in place is something you can set either way-- and you can set it either way AFTER the s-path photon has hit the screen. So, can you make the decision deliberately go the opposite of what the s-path photon told you?
Just to be clear, you don’t observe interference patterns in single individual photons. This video should give you an idea of how interference patterns are observed when you pass one photon at a time through a double slit.
But as HMHW has already pointed out it’s the coincident count that actually appears on the graphs that demonstrate interference. If you don’t have knowledge of that then you can’t the interference pattern from detector D[sub]s[/sub].
With the polarizer in front of it, the p-path detector records only about half the photons the s-path detector does; this information tells you which s-detections to keep, so to speak, in order to build the interference pattern.
Some questions about the double slit experiment:
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When we are sending electrons one by one, it appears as if the same electron passed through both slits at the same time. But how many hits are registered on the screen? Is it just one or two? Or we do not have the technology to detect single electrons so the need to make several iterations of the experiment to get the interference pattern?
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In all those double slit experiments the polarizers are placed before the slits. Would it make any difference if they were placed right after the slits?
One.
I assume by “polarizer” you mean the quarter wave plates in the s beam. Then no, it shouldn’t matter. (There’s possibly a small difference in the number of photons transmitted depending on if they are polarized parallel to the slits or perpendicular. That could lead to a small difference if the order of the quarter wave plates and the slits were swapped. But at the level of this discussion, it’s not important.)