Frequency or wavelength of a photon

[Rade]

...The reason you can't detect two photons is simply because,their aren't two photons in Feynmans two slit just one,you need to grasp the concept of superposition and that it is decohered by striking a slit all the other "circles" disappear...

Thanks very much for your explanation and time. One last question based on the above statement (maybe). Suppose a situation where there were "two photons" (eg, simultaneously at both sites) and not "just one"--do you know of any experimental design at could detect "two photons simultaneouly" at the slits--can you provide a reference ?

 

[marlon]

that is, it is not possible to detect (AT BOTH SLITS SIMULTANEOUSLY) any single photon going through two slits ||+|| at EXACTLY THE SAME TIME AT BOTH SLITS. {edit} That is, of course we only see what happens at one slit or another, because it is not physically possible to detect at both slits simultaneously, EVEN IF THE PHOTON WAS IN REALITY AT BOTH SLITS SIMULTANEOUSLY--

The fact that "the photon passes through both slits" is a direct consequence of the QM formalism, ie the superposition of both slits in the photon's wavefunction. I think we all agree on that. Now, that same formalism clearly proves that if you measure at the slits, the superposition in the photon's wavefunction is broken. So you no longer have this sum of "passing through slit 1" and "passing through slit 2". In this case, the photon will pass either through slit 1 OR slit 2, as we will indeed observe if we measure at the slits. THAT IS ALL THERE IS TO IT.

To be clear, if we do not measure at the slits, the formalism only states that we do NOT know what trajectory the photon is following. We only know that there is wavelike behaviour as we observe at the detector. So, actually talking about "a photon that passes through both slits" is meaningless and useless.


marlon

 

[Rade]

...actually talking about "a [single] photon that passes through both slits" is meaningless and useless.

Thank you Marlon, I now understand the essence of the concept "constraint" in quantum mechanics.

 

[marlon]

Thank you Marlon, I now understand the essence of the concept "constraint" in quantum mechanics.

I am not quite sure what you mean here. Just to be sure, a single photon does give us interference patterns and one could indeed say "that is passes through both slits" but using this language is confusing if one is not familiar with the underlying concept. That is what i wanted to say.

marlon

 

[Haelfix]

Feynman lectures, volume 3, chapter 1.

No clearer account has ever been written about the fundamental problem of QM.

 

[Schrodinger's Dog]

Thanks very much for your explanation and time. One last question based on the above statement (maybe). Suppose a situation where there were "two photons" (eg, simultaneously at both sites) and not "just one"--do you know of any experimental design at could detect "two photons simultaneouly" at the slits--can you provide a reference ?

Your welcome, I had the same questions as you going into learning about it, luckilly though I found a discussion on here and then followed some links and found a few of my own. I saw the others description and I figured they may be using concepts you weren't familliar with so I tried to put it in very simple language, a sort of idiots guide, the same sort of information I had when I was learning about it, without getting to heavilly involved in maths or relatively obsucre terms too early on. Now go and learn about special relativity, that's a bit of a mind melt at first too