# Polarization, Bell, and spin of photons

1. Nov 1, 2014

### jk22

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.

2. Nov 1, 2014

### Staff: Mentor

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)

3. Nov 2, 2014

### jk22

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 ?

4. Nov 2, 2014

### Staff: Mentor

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.

5. Nov 2, 2014

### naima

Last edited: Nov 2, 2014
6. Nov 4, 2014

### jk22

So the fact that helicity has only two value implies that it can be modelized with pauli matrices.

7. Nov 4, 2014