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I encountered the following sentence in my textbook, which I don't quite understand, and after an unfruitful google search, I still can't figure out what they mean by magnitude in this context:

..."split a photon into N components with magnitude ϵ"?

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sounds wrong in my opinion. Missprint or something. A photon is one of the elementary particles, cannot be split, it has mass 0 and is only characterized by its energy/frequency and spin orientation (=/-1). – anna v May 23 '13 at 13:01
It does not make sense at all. One can split classical electromagnetic waves, not individual photons. There is nothing there to split. what is the book? – anna v May 23 '13 at 13:35
Maybe they mean that they send the photon on a beam splitter (or a set of them) so that, technically, the photon is "split" into all the output modes. The formulation is not ideal but that might also depend on the context in which the whole formulation is used. – Ondřej Černotík May 23 '13 at 14:05
@OndřejČernotík a photon is an individual particle withe energy hnu and a spin (+/-1). It cannot be split. It can Compton scatter on an electron and change its frequency, be absorbed kicking an electron to a higher level, or pair produce in the field of a nucleus for high energy gammas. thats about all. – anna v May 23 '13 at 14:11
@annav I know that. What I mean is that they probably mean splitting its probability amplitude among several modes. It's not the same thing and the term "splitting a photon" is definitely not a suitable one, but this is where I think the core of the statement might be. – Ondřej Černotík May 23 '13 at 14:46

Thats nonsense. In Spontaneous parametric down-conversion, one photon may produce two photons with half the energy. No one refers to them as components. The term "magnitude" is unusual in the context of photons. Photons have energy and spin.

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