How Does Photon Spin Relate to Frequency and Polarization?

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Discussion Overview

The discussion revolves around the relationship between photon spin, frequency, and polarization, exploring concepts such as circular and linear polarization, state vectors, and the implications of measurements on photon states. Participants raise questions about the nature of photon spin, the basis for polarization, and the potential spatial dependence of polarization measurements.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants question whether photons have only integer spin or if chirality is the primary consideration, linking this to the relationship between spin and frequency.
  • There is a debate about whether left and right circularly polarized photons represent a 'natural' basis for photons, with some arguing that any basis is valid and that circular polarization is a convention.
  • Concerns are raised about the implications of variable frequencies for circular polarization across different colors of light, with some asserting that these frequencies do not need to match.
  • Participants discuss the potential for spatial dependence in measuring circularly polarized photons in linear polarization states, with differing views on whether periodicity exists in such measurements.
  • One participant suggests that coherent circularly polarized photons may exhibit changing probabilities of linear polarizations, while another counters that only the phase changes, not the amplitudes.
  • State vectors for various polarization states are proposed, with a later correction indicating that the weights should be complex rather than real, leading to further discussion on the nature of these state vectors.
  • There is a contention about whether spatial dependence exists in the context of photon propagation and measurement, with differing interpretations of the implications of speed and frequency.

Areas of Agreement / Disagreement

Participants express differing views on several key points, including the nature of photon spin, the validity of different polarization bases, and the existence of spatial dependence in polarization measurements. No consensus is reached on these issues.

Contextual Notes

Limitations in the discussion include assumptions about the nature of photon states, the definitions of polarization bases, and the implications of measurement processes that remain unresolved.

Who May Find This Useful

This discussion may be of interest to those studying quantum mechanics, particularly in the context of photon behavior, polarization, and the mathematical representation of quantum states.

Prologue
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I've got three questions basically.

  1. Do photons actually have only an integer spin +/- 1, or do people really only mean the sign of its chirality? The reason I ask is that I am interested in whether the photon spin is related to its frequency. This leads to the next question.
  2. Is the basis for Left and Right circularly polarized photons the 'natural' basis for photons? Or is it the linear polarization basis? Photons have spin and so I am betting that the 'natural' basis is the circularly polarized one. But, if it turns out that in (question 1) they all have the same spin frequency, then it presents a problem - the variable frequencies needed to make circular polarization of different colors of light wouldn't match up then because all the different colors would need different frequencies of 'rotation'.
  3. This last one probably hinges on the first two. Is there a spatial dependence on the probability of finding a circularly polarized photon in a linear polarization state? In other words, will there be periodic points in space where it is more probable to measure a vertical polarizations versus a horizontal polarization - (the periodicity would be based on the frequency of rotation of the circularly polarized photon)?

Ok, depending on what comes out to be true, the 3rd question might be an analogy for neutrino oscillations - you know, how there is a periodic dependence on space in what you measure for the probability of a certain state.
 
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1. Do photons actually have only an integer spin +/- 1, or do people really only mean the sign of its chirality? The reason I ask is that I am interested in whether the photon spin is related to its frequency. This leads to the next question.
It is not related to the frequency.

Is the basis for Left and Right circularly polarized photons the 'natural' basis for photons?
Any basis is as good as any other. Physicists use circular left and right handed, but it's just a convention.

the variable frequencies needed to make circular polarization of different colors of light wouldn't match up then because all the different colors would need different frequencies of 'rotation'.
Any frequency mod can have it's own polarization and they don't need to match.

Is there a spatial dependence on the probability of finding a circularly polarized photon in a linear polarization state? In other words, will there be periodic points in space where it is more probable to measure a vertical polarizations versus a horizontal polarization - (the periodicity would be based on the frequency of rotation of the circularly polarized photon)?
There is no such periodicity.

Even if it was - one measurement of polarization destroys original photon state, so any subsequent measurements in other points will not give you any more data about the photon.

You can always express circular polarized photon as a combination of two linearly polarized ones. You can do it at any point and for any two orthogonal polarizations. You seem to think that the amplitudes of linear components change with time, but they don't. It's only their phase that changes, but it doesn't manifest as change of probability.
 
I am not talking about subsequent measurements of the same photon, but measurements on identical photons emitted coherently from the same source but then measured at different distances.

You seem to think that the amplitudes of linear components change with time, but they don't. It's only their phase that changes, but it doesn't manifest as change of probability.

So coherent circularly polarized photons don't have changing probabilities of linear polarizations? I find that hard to believe but only from an intuitive standpoint. I am having trouble finding state vectors defined in a nice way to demonstrate these intricacies so maybe you could write down what they are like. I'll guess at what they are below and maybe you can tell me where I am wrong, then show the correct ones.

What is the state vector for a vertically polarized photon?
[tex]\Psi_{v}=|v\rangle[/tex]
For a horizontally polarized photon?
[tex]\Psi_{h}=|h\rangle[/tex]
For an arbitrary linear polarized photon?
[tex]\Psi_{\theta}=|\theta\rangle=\sin{\theta}|v\rangle + \cos{\theta}|h\rangle[/tex]

For a LHCP photon?
[tex]\Psi_{L}=|L\rangle=\sin{\omega t}|v\rangle + \cos{\omega t}|h\rangle[/tex]
A RHCP photon?
[tex]\Psi_{R}=|R\rangle=\sin{(-\omega t)}|v\rangle + \cos{(-\omega t)}|h\rangle[/tex]
An elliptically polarized photon?
[tex]\Psi_{Ell}=|Ell\rangle=\alpha\sin{\omega t}|v\rangle + \beta\cos{\omega t}|h\rangle[/tex] where [tex]|\alpha|^{2}+|\beta|^{2}=1[/tex]

Etc. These are merely guesses at what they'd be because I haven't managed to find a source for this info yet.
 
Prologue said:
For a LHCP photon?
[tex]\Psi_{L}=|L\rangle=\sin{\omega t}|v\rangle + \cos{\omega t}|h\rangle[/tex]
A RHCP photon?
[tex]\Psi_{R}=|R\rangle=\sin{(-\omega t)}|v\rangle + \cos{(-\omega t)}|h\rangle[/tex]
An elliptically polarized photon?
[tex]\Psi_{Ell}=|Ell\rangle=\alpha\sin{\omega t}|v\rangle + \beta\cos{\omega t}|h\rangle[/tex] where [tex]|\alpha|^{2}+|\beta|^{2}=1[/tex]

No no. It's not like that. The weights should be complex, not real.
It's more like:
[tex]|L\rangle=(\exp{(i \omega t)}|v\rangle + \exp{(i \omega t + \pi / 2)}|h\rangle) / \sqrt{2}[/tex]
Each weight is a complex number that changes with time, but its module remains constant. (Square of module is always [tex]\sqrt{2} / 2[/tex].)

I'm not sure if I'm exactly correct, but it should go like that.
 
Ok, but even in that setup there seems to be a spatial dependence to me. Since they move at the speed of light, and [tex]\frac{\omega}{k}=c[/tex], I think there will be a spatial dependence (as long as that state is correct).
 
Amplitudes of the linear components don't change. Only their phase changes. So at any point you will have the same probability of detecting linearly polarized photon ([tex]\sqrt{2}/2[/tex] of original photon).
 

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