Talk:Photon polarization

message: 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)
replies: text: three polarization orientations only for massive particles, this is a classic result 2A01:E0A:159:17E0:D088:2EC0:89C6:76C2 (talk) 15:46, 2 October 2023 (UTC)

text: No. Three polarisation base orientations are only possible for waves travelling slower than the universal speed limit. At the speed limit (i.e. for light), relativistic effects remove the longitudinal mode. I do not have a very good explanation, but a clue might be the observation that for anyone travelling at the speed limit, length contraction reduces the universe's dimensionality to two, i.e. the universe has no expansion anymore in the direction of flight.WikiPidi (talk) 14:27, 9 March 2020 (UTC)
thread_title: Light has three polarization orientations, not just the two

message: 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)
thread_title: Error: In the section Uncertainty Principle and Mathematical preparation 

message: 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)
replies: text: 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)
thread_title:  [[Photon]] article says that a photon has ''two possible polarization states'' 

message: 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)
replies: text: 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)
replies: text: See my long comment below. 178.38.18.115 (talk) 07:55, 27 June 2015 (UTC)
thread_title:  article says that a photon can have zero angular momentum 

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

message: 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} \ge \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)
replies: text: Dear Schief, I would also like to know this, thanks for asking. 178.38.18.115 (talk) 07:20, 27 June 2015 (UTC)
replies: text:  I do not have a particular source for this relation, but you need to realise that you can write uncertainty relationsships like this for any couple of canonically conjugated variables. The one with x and p is only one (and not even a special) case, in quantum mechanics you derive p=d/dx (this should be a partial derivative), i.e. the momentum is proportional to the derivative with respect to position, which makes them conjugated. Similarly, E=d/dt (time evolution, Schrödinger equation), so energy and time build another uncertainty relation, and in the same way L=d/dAngle. WikiPidi (talk) 14:18, 9 March 2020 (UTC)
thread_title:  Source for uncertainty relation in "Application to angular momentum" 

message: See http://www.dailymail.co.uk/sciencetech/article-3644747/Does-Nasa-s-fuel-free-thruster-invisible-exhaust-New-theory-explain-EmDrive-man-Mars-10-weeks.html  — Preceding unsigned comment added by 90.154.68.99 (talk) 18:33, 23 June 2016 (UTC)
thread_title:  zero polarization possible? 

message: The long quotation from Dirac's book was tagged dubious in two places in this diff: . The reasons for the tags are given in the tags, where it is unlikely to be seen by readers (they are visible in the diff). It seems to me that this is WP:OR. If Dirac needs correcting it should be in the article and cited from a published reliable source. If we feel the Dirac quote is too misleading and we don't have a way to include a clarification, we can delete the quote. Either way, the tags should go.--agr (talk) 15:04, 27 December 2017 (UTC)
thread_title:  Dirac dubious tags 

message: I am new at this, so I'm not confident.
If unit vectors are defined such that
:   |\mathrm{R}\rangle  \ \stackrel{\mathrm{def}}{=}\    {1 \over \sqrt{2}} \begin{pmatrix} 1    \\ i  \end{pmatrix}    
and
:   |\mathrm{L}\rangle  \ \stackrel{\mathrm{def}}{=}\    {1 \over \sqrt{2}} \begin{pmatrix} 1    \\ -i  \end{pmatrix}    
then an arbitrary polarization state can be written in the "R-L basis" as
:   |\psi\rangle   = \psi_{\rm R} |\mathrm{R}\rangle + \psi_{\rm L} |\mathrm{L}\rangle  
where
:\psi_{\rm R} = \langle \mathrm{R}|\psi\rangle = \frac{1}{\sqrt{2}}(\cos\theta\exp(i\alpha_x) - i\sin\theta\exp(i\alpha_y))
and
:\psi_{\rm L} = \langle \mathrm{L}|\psi\rangle = \frac{1}{\sqrt{2}}(\cos\theta\exp(i\alpha_x) + i\sin\theta\exp(i\alpha_y)).
Are the signs reversed here?
Jethomas5 (talk) 08:56, 30 August 2022 (UTC)
thread_title:  Is this right?