# Question for understanding photon entanglement

1. Aug 1, 2012

### Philosifur

Photon Entanglement Question
Polarize a string of photons vertically. Make the polarized photons into two streams of vertically polarized entangled photon pares. One photon of each pare will go to point A and the other will go to point B. All photons that arrive at point A will encounter a polarizer filter set at 45 degrees clockwise with a photon detector after the filter. The photons arriving at point B will have a small longer path length with will delay the photon reaching the planarization filter by a few microseconds. The photons arriving at point B will be divided into two streams, where half will encounter a polarizer filter 45 degrees clockwise and the other half will encounter a polarizer filter 45 degrees counterclockwise. A photon detector will follow each polarizer filter. What will the statistical results be?

2. Aug 1, 2012

### DrChinese

Welcome to PhysicsForums, Philosifur!

Polarization entangled photon pairs - by definition - cannot be vertically polarized. They must have an undefined polarization which is either the same or orthogonal (crossed). Which they will be is dependent on the process by which they were created.

However, your experiment still can be used to generate correlations between the 2 streams. They will be matched 50% of the time, i.e. no correlation. That is because the difference between the 2 angles (A and B) is always 45 degrees whether B is 45 degrees clockwise or counterclockwise. The formula for matches in that case is cos^2(45 degrees) = .50 which is the same as flipping a coin.