My previous thread on this topic got a bit messy as the gist of the argument was in the middle of the thread and turned out wrong. Hence this new updated version.(adsbygoogle = window.adsbygoogle || []).push({});

One of my favourite articles on Bell's Theorem can be found at

http://www.upscale.utoronto.ca/GeneralInterest/Harrison/BellsTheorem/BellsTheorem.html.

Even though it is geared towards the laymen, I'm having trouble applying the particle spin example to particle polarisation. I would very much appreciate if anyone could check the following reasoning for me:

Assuming the polarisation filters can be set to 3 angles: -30 degrees, 0 degrees, 30 degrees, I have the following states:

A : polarisation of photon after passing a -30 degree filter in the left detector

!A : polarisation of photon after passing a -30 degree filter in the right detector

B : polarisation of photon after passing a 0 degree filter in the left detector

!B : polarisation of photon after passing a 0 degree filter in the right detector

C : polarisation of photon after passing a 30 degree filter in the left detector

!C : polarisation of photon after passing a 30 degree filter in the right detector

I attach a little sketch here that describes the situation.

Bell's Inequality states: N(A !B) + N(B !C) >= N(A !C)

Problem I have is that the inequality for polarisation seems to fit for MISMATCHES, i.e for the photons that are NOT matching:

For local reality:

delta 30 degree mismatch + delta 30 degree mismatch >= 2 times delta 30 degree mismatch, or 1/4 + 1/4 >= 1/2

And for entangled photons:

delta 30 degree mismatch + delta 30 degree mismatch >= delta 60 degree mismatch, or 1/4 + 1/4 >= 3/4, which violates Bell's inequality (as it should).

Is this reasoning correct? And if so, why do I need to consider mismatches instead of matches?

**Physics Forums - The Fusion of Science and Community**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# B Bell's Inequality && polarisation for the layman

Have something to add?

Draft saved
Draft deleted

Loading...

Similar Threads - Bell's Inequality polarisation | Date |
---|---|

B Understanding Bell’s inequality | Jan 6, 2018 |

B A question about Bell's Inequality and hidden variables | Oct 8, 2017 |

B Proving entanglement using polarisation & Bell's Inequality | Feb 26, 2016 |

Bell inequality experiments and photon polarisation issue | Dec 27, 2011 |

**Physics Forums - The Fusion of Science and Community**