Talk:Linear optics

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Wrong: Non-Linear Optics != Linear Optics. Removing redirect Change to correct Ray_transfer_matrix_analysis

Need to partially reverse a recent modification

1. A recent modification done by Sbyrnes321 is partially great, but in my eyes contains two errors that ought to be reversed: Being linear in the sens ethat if A goes to B and C goes to D then A+B goes to C+D is correct both for linear optics and for nonlinear optics. This is so because quantum physics is linear. 2. The same recent modification done by Sbyrnes321 contained deleting the following, that ought to be put back because it is most relevant and it is correct: "In linear optics (from quantum optics point of view), the unitary transformation on a single photon strictly determines the unitary transformation on any number of photons, while in nonlinear optics it does not."

If there are no objections - I will apply those modifications after waiting some time and mentionning them to Sbyrnes321. Tal Mor (talk) 20:25, 29 March 2017 (UTC)

Let's start with (1). "If a system transforms light input A into output B, and input C into output D, then an input consisting of A and C simultaneously give an output of B and D simultaneously." I still believe that this statement is not true in nonlinear optics. Let's say A is red light (450THz) and C is IR light (140THz). With A+C simultaneously passing through a nonlinear crystal, you can get 450THz + 140THz = 590THz green light out (sum frequency generation), whereas neither B nor D by itself would emit 590THz green light.

Yes quantum physics is linear in a certain sense, but not in this sense. In quantum physics, the "sum" of A and C is "a quantum superposition between a beam of red light and a beam of green light". The situation where both red light and green light are simultaneously present is not represented in this superposition, and therefore nor would be any possibility of 590THz green light. I personally think the current wording of the article implies the everyday sense of superposition (red light + green light = both red light and green light simultaneously), not the quantum sense (red light + green light = quantum superposition of red light with green light but not both simultaneously), and that is as it should be. But if you think it's ambiguously worded, we can discuss how to change it... --Steve (talk) 21:10, 29 March 2017 (UTC)

Can we focus more on the second issue? It is much more vital, as the MAIN point in linear optics is that if you know what happens to |10000...00> (say, K modes, and a single photon in the left-most mode) then you know what happens to |n0000...00> for any n. Do you agree with that? Tal Mor (talk) 14:28, 3 April 2017 (UTC)

Correct, I don't like the sentence "In linear optics (from quantum optics point of view), the unitary transformation on a single photon strictly determines the unitary transformation on any number of photons, while in nonlinear optics it does not." Why not? Well I don't disagree with it, I just think it's a jargon-y and obscure way to say something that's actually very simple. I would say it in a more down-to-earth way, maybe something like: "In linear optics systems, like lenses and mirrors, if you increase the intensity of the input light, then that increases the intensity of the output light in direct proportion, and it does not change the output light in any other way. In nonlinear optics, by contrast, changing the input intensity can alter the output in many different ways." (And maybe give some examples.) OK well I'm sure there's room for improvement but I hope you see what I'm going for. I believe that this kind of description can be every bit as precise, general, and technically correct as the sentence you like, but a much larger fraction of readers will be able to understand it. --Steve (talk) 00:17, 4 April 2017 (UTC)