Talk:Photon polarization

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Light has three polarization orientations, not just the two

Hi, About the first sentence in this article "Photon polarization is the quantum mechanical description of the classical polarized sinusoidal plane electromagnetic wave. Individual photons are completely polarized. " - would you call a photon in a superposition of several polarizations (e.g. as the ones used to prove that bell's inequality does not hold) completely polarized? -Lars —Preceding unsigned comment added by Laser Lars (talk • contribs) 09:32, 27 October 2008 (UTC)

light has three polarization orientations, not just the two mentioned in the artical

Snowflakeuniverse 18:00, 10 January 2007 (UTC)

- light has n polarization orientations, one for each dimension in whatever spatial metric you are operating. Dfruzzetti (talk) 21:24, 31 December 2008 (UTC)

Error: In the section Uncertainty Principle and Mathematical preparation

Error: In the section "Uncertainty Principle" and under the heading "Mathematical preparation" you will find a diagram representing two intersecting vectors v and w and their intersection is incorrectly labeled cos(a). On the diagram, the angle should have measure a rather than the cosine of that measure.

Dfruzzetti (talk) 21:23, 31 December 2008 (UTC)

Photon article says that a photon has two possible polarization states

The Photon article says that a photon has two possible polarization states. This article does not refer to this, but describes the polarization state in terms of a Jones vector, which has three parameters. These two statements seem very inconsistent, and there doesn't seem to be any explanation linking the two. Is there a standard way to represent a polarization state using two parameters? cojoco (talk) 03:14, 26 March 2010 (UTC)

The two possible polarization states the photon article refers to are probably the two basis vectors for the polarization state space, either it be $|x\rangle$ and $|y\rangle$, or $|R\rangle$ and $|L\rangle$ (or any other two orthogonal basis vectors, which two doesn't really matter). To say that the photon only have two possible polarization states clearly seems wrong to me, since it can be in any superposition of the two basis states. On the other hand, upon measurement of which polarization state the photon is in, you will only be able two get two different results (both with different probabilities), which depend on how you perform the measurement (see wave function collapse). --Kri (talk) 14:06, 28 May 2011 (UTC)

article says that a photon can have zero angular momentum

The article says "Photons have only been observed to have spin angular momenta of ±ħ or 0." ±ħ was observed by Beth - Beth, Richard. 1936. “Mechanical Detection and Measurement of the Angular Momentum of Light.” Physical Review 50 (2): 115-125. doi:10.1103/PhysRev.50.115. Photons cannot have zero angular momentum in the direction of propagation. 144.131.117.96 (talk) 00:29, 29 March 2011 (UTC)andrew

Note that the point about saying that a particle is of spin n is that a measurement of its intrinsic angular momentum must be in the set $\{-n\hbar ,-(n-1)\hbar ,...,(n-1)\hbar ,n\hbar \}$. For bosons, zero is a possibility. "Photons have only been observed to have spin angular momenta of ±ħ or 0." is a correct statement, since it does not make any reference to direction of motion. Ricieri (talk) 02:39, 20 August 2014 (UTC)

Repetition

This article repeats, pointlessly, vast amounts of stuff from sub-articles William M. Connolley (talk) 20:52, 24 March 2012 (UTC)

I agree. Further, the article is supposed to be about the polarization of a light quantum, not the collective polarization. Kbk (talk) 02:30, 5 September 2013 (UTC)

Linearly polarized photons?

Isn't this claim false: "Individual photons are completely polarized. Their polarization state can be linear or circular, or it can be elliptical, which is anywhere in between linear and circular polarization." I don't think an individual photon can have any polarization state other than left or right circular. Am I mistaken?

From Mathpages.com: "...each absorption of a photon, imparts either +h or -h to the absorbing object, so if the intensity of a linearly polarized beam of light is lowered to the point that only one photon is transmitted at a time, it will appear to be circularly polarized (either left or right) for each photon, which of course is not predicted by classical theory."--Srleffler (talk) 06:11, 21 October 2013 (UTC)

I completely agree! You cannot have linearly polarized photons. They are either completely circularly polarized: right or left. According to the current theory which is referenced by Srleffler, there is no such thing as a linearly polarized photon. --Srodrig (talk) 07:18, 12 December 2013

The state space must be a Hilbert space. You get a value for the angular momentum only if you measure that. If the value can be h, 0, or -h, the Hilbert space must have complex dimension at least 3. But it is complex dimension 2 in the article, and the operator is given concretely; its eigenvalues are h and -h.

Of course that state can also be any superposition of the two chiral states. For example, if they occur with equal magnitude, then the photon will be linearly polarized, meaning that it is an eigenstate of a linearly polarizing filter operator (which is a projection onto a linearly polarized state). This is still a pure state, by the way. It is only if we insist on measuring angular momentum that the state switches to an eigenstate of angular momentum.

178.38.18.115 (talk) 22:40, 26 June 2015 (UTC)

Source for uncertainty relation in "Application to angular momentum"

It would be great to have a citation or reference for the uncertainty relation in the section "Application to angular momentum": $\Delta {\hat {l}}_{z}\,\Delta {\theta }\geq {\frac {\hbar }{2}}$.

I just briefly searched the web and some books on quantum optics. It seems that this kind of uncertainty relation, relating the polarization angle and angular momentum, is not very common. So, it would be nice to elaborate a bit on that or add a reference for better understanding. I would be interested in some explanations or derivations myself. How is the general relation in 3D?

--Schiefesfragezeichen (talk) 08:53, 24 June 2014 (UTC)