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> Ask any working QM researcher to clearly show how "a single photon" interacts with an electron in an orbital and they will without a doubt draw you a cartoon
by Ono-Sendai 6y ago
> Ask any working QM researcher to clearly show how "a single photon" interacts with an electron in an orbital and they will without a doubt draw you a cartoon diagram. Never in the history of theoretical physics has anyone, ever, anywhere made a numerical visualisation of this.
I personally have made a simulation of this.
It would be called a semi-classical approximation, in that it's a simulation of a Schrodinger equation-described electron in a hydrogen (Coulomb) potential interacting with a classical EM wave. However I suspect that's how nature works anyway.
- jiggawatts 6y agoI'd love to see the video of this, or even a still picture. If you have some time, please upload it to YouTube or something, because it would be the only such video on there. It would have significant educational value.
- Ono-Sendai 6y agoOk yeah I'll dig up the code and capture a video of it. I'm currently working on a Dirac equation simulation which should give a more accurate picture of an electron.
- eigenspace 6y ago> However I suspect that's how nature works anyway. Uh, could you clarify what you mean here? Are you saying you don't beleive that the electromagnetic field is quantized?
- Ono-Sendai 6y agoYeah pretty much. (I say this not from a position of profound knowledge or anything like that, just that I'm not familiar with a good argument for why it is, not that I have looked into it in great detail. My knowledge of QFT is very basic)
- eigenspace 6y agoAh, fair enough. I was worried you might be professing some sort of expertise while claiming that. I can assure you that whatever may be true of the electromagnetic field, it is not classical. We know that to about the same degree of certainty that we know that atoms aren't classical. It's just that when considering atoms in an electromagnetic field, there are often situations where you can ignore the quantum mechanics of the field.
- Ono-Sendai 6y agoSo what would you say is the best evidence that the EM field is quantised?
- eigenspace 6y agoExamples abound, but I’d say my favourite is the electron g-factor which is an example of one of the most precise agreements between theory and experiment ever achieved by humans and it’s calculation relies heavily on the quantum mechanics of the electromagnetic field. But there’s lot of other, more pedestrian examples. For example, you can (and people have) generated entangled pairs of photons and then performed measurements on this entangled pairs that violate the Bell inequalities, meaning that their correlation is not classical.
- eigenspace 6y agoLooking back on this, I feel I should also mention that there's not any single piece of evidence that should be bullet-proof convincing evidence for the EM field's quantum nature, rather it's the totality of many many many different, independent results exploring various quantum mechanical properties of electromagnetism (and its high energy unification with the weak nuclear force), all of which converge on the basically undeniable fact that electromagnetism is a quantum mechanical phenomenon. Of course, this isn't the full story. There is physics beyond the standard model. But whatever that physics is, it's description needs to reproduce quantum electrodynamics in the appropriate limit. I should also mention that it's not even mathematically consistent to have a classical field like electromagnetism coupled to quantum matter. It's fine in certain approximation schemes, but the breakdown and limitations of such an approach is well documented.