High School Photon detection in the EPR experiment

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In the EPR experiment, photon detection involves using linear beam splitting polarizers to determine the final polarization state of the photon. The discussion clarifies that all polarizing beam splitters split the photon beam into two directions, rather than having one output that absorbs part of the beam. For polarizers that change the direction of the photon, detectors are positioned where the photon is expected to arrive based on the polarizer's orientation. In cases where the polarizer does not alter the direction, an additional polarizer with a fixed orientation may be necessary to separate the states before detection. Understanding these mechanisms is crucial for accurately detecting the polarization state in the EPR setup.
kurt101
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In the photon version of the EPR experiment, how is the final polarization state of the photon detected?

I have read a number of high level descriptions of the EPR experiment, but I am having trouble with understanding the detection part.

Here is my understanding, please correct me where I am wrong.

I understand the type of polarizer used in the EPR experiment is a linear beam splitting polarizer as defined here https://en.wikipedia.org/wiki/Polarizer

If I understand correctly, there are some linear beam splitting polarizers that split the photon into 2 directions and there are some that do not. Just to be clear, I am not referring to the polarization state vector, but the direction the photon is traveling as it leaves the polarizer.

So I can imagine that for a beam splitting polarizer that does alter the direction of the photon, the detector would be a photon detector placed in the location of where the photon is expected to arrive for a given polarizer orientation.

Or I can imagine that for linear beam splitting polarizer that does NOT alter the direction of the photon, the detector would need to include another polarizer (absorption or beam splitting type) that has a fixed orientation relative to the EPR experiment in order to split the two states prior to being detected by a photon detector.

Are either of these ways of detecting the final polarization of the photon in the EPR experiment valid? Are there other ways?
Thanks
 
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You should first read about classical crystal optics. In its full glory it's marvelously explained in the good old book by Sommerfeld:

A. Sommerfeld, Lectures on Theoretical Physics, vol. IV (optics)

Then you can think of this as an effective theory describing also the interaction of single photons with the optical elements like your polarizer.
 
kurt101 said:
If I understand correctly, there are some linear beam splitting polarizers that split the photon into 2 directions and there are some that do not. Just to be clear, I am not referring to the polarization state vector, but the direction the photon is traveling as it leaves the polarizer.
All polarizing beam splitters are splitting photon beam in two direction. Polarizing beam splitter with one output does not make sense. Polarizer has one beam at the output, but it absorbs part of the beam so that the beam is altered anyways.
kurt101 said:
So I can imagine that for a beam splitting polarizer that does alter the direction of the photon, the detector would be a photon detector placed in the location of where the photon is expected to arrive for a given polarizer orientation.
Yes
 
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. Towards the end of the first lecture for the Qiskit Global Summer School 2025, Foundations of Quantum Mechanics, Olivia Lanes (Global Lead, Content and Education IBM) stated... Source: https://www.physicsforums.com/insights/quantum-entanglement-is-a-kinematic-fact-not-a-dynamical-effect/ by @RUTA

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