# Feynman Quote

1. Jul 28, 2012

### JPBenowitz

1. The problem statement, all variables and given/known data

I don't really know where to post this but I chose this section. I need help finding the source of this Feynman Quote "The probability of detecting a photon at any point is the sum of all the probabilities of the photon being detected at that point by any path"

2. Relevant equations

3. The attempt at a solution

2. Jul 29, 2012

### fzero

3. Jul 29, 2012

### phinds

Since this is one of his fundamental principles, he said it many times and very likely wrote it many times as well.

4. Jul 29, 2012

### TSny

If that's a direct quote, then he must have been speaking loosely. It's the probability amplitudes for all the paths that are added to get the total probability amplitude. You then "square" the total amplitude to get the total probability. The distinction between adding amplitudes and adding probabilities is fundamental to quantum mechanics.