Polarization, Bell, and spin of photons

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Discussion Overview

The discussion revolves around the relationship between photon polarization, Bell inequalities, and the spin of photons. Participants explore the implications of measuring polarization through polarizers, the connection between electric field orientation and quantum states, and the distinction between photon spin and polarization.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether the electric field orientation after measurement can be assimilated with a vector in Hilbert space and how this relates to normalization in quantum mechanics.
  • Another participant explains that in polarizer experiments, there are only two outcomes for a photon: it either passes through the polarizer or is absorbed, with a 100% probability for one of these outcomes.
  • A participant raises the question of what the measurement result of 0 corresponds to in the context of spin-1 particles and their polarization states.
  • It is noted that the polarization of a photon is distinct from its spin, with a participant asserting that measuring polarization involves using a polarizer oriented in the direction of interest.
  • Another participant mentions that massless particles like photons only have helicity values of +1 or -1, suggesting that the null value does not apply to photons.
  • One participant proposes that helicity can be modeled using Pauli matrices due to its two possible values.
  • A reference to an external forum is provided, discussing the relationship between helicity and spin for particles.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between photon polarization and spin, with some asserting their distinction while others explore their connections. The discussion remains unresolved regarding the implications of measurement outcomes and the interpretation of helicity.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the relationship between polarization and spin, as well as the definitions of measurement outcomes in quantum mechanics.

jk22
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i have the following questions: Bell inequalities use spin 1/2 matrices and experiments use photons. Is then the electric field horizontal or vertical after the measurement with a polarizer in other words can we assimilate the orientation of the field with a vector in the hilbert space ? How does this correspond to the quantum rule that the endstate should be normalized if the photon after measurment has less intensity ?

But photons are spin 1 particle a boson, so then which state of the electrical field corresponds to the third quantum measurement result ?

Thanks.
 
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The three measurements in these experiments are made by orienting the polarizer at three different angles. No matter what the polarization of the incoming photon, there are only two possible outcomes (in the idealized situation) when it encounters the polarizer: either it passes through the polarizer and its polarization is now aligned with the polarizer; or it is absorbed.

There is a 100% probability that one of those two outcomes will happen. If the photon passes the polarizer, then we renormalize its wave function to reflect the new state: there is a 100% probability that the photon is in a state consistent with it having passed the polarizer.

(You may want to spend some time understanding the quantum mechanical description of single-polarizer experiments before you dig into the subtleties of the two-polarizer experiments involved in tests of Bell's theorem)
 
I meant for spin 1 we measure the polarization once we can get 1,-1 and 0 which corresponds to polarization let say vertical horizontal and what does 0 corresponds to ?
 
jk22 said:
I meant for spin 1 we measure the polarization once we can get 1,-1 and 0 which corresponds to polarization let say vertical horizontal and what does 0 corresponds to ?

The polarization of a photon has nothing to do with its spin.

You measure the polarization of a photon in a given direction by using the procedure I described above: send the photon through a polarizer oriented in the direction of interest. There are only two possible results, passing and not passing.
 
So the fact that helicity has only two value implies that it can be modelized with pauli matrices.
 

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