“If you were to throw 10 billion photons at a polarizing filter, and the average probability of each one going through is, say, 3/4, you would expect 3/4 of 10 billion would get through. Likewise, the energy that they would carry would be 3/4 of the energy that you attempted to put through. Classical theory says nothing about the statistics of the thing—it simply says that the energy that comes through will be precisely 3/4 of the energy which you were sending in. That is, of course, impossible if there is only one photon. There is no such thing as 3/4 of a photon. It is either all there, or it isn’t there at all. Quantum mechanics tells us it is all there 3/4 of the time.” – Richard P. Feynman, The Feynman Lectures on Physics, Vol. III