Hello,

after having viewed the video on the Delayed Choice Quantum Eraser, in the Classroom: Physics X, I got a question.

As a single photon laser beam hits the double slit it can either go through both A and B or only A or B. This is written here:

http://en.wikipedia.org/wiki/Delayed_ch ... tum_eraser under "The experiment"

But, as I can see from the drawing of the experiment, if a photon goes through A and B we get 4 (single and idle X 2) new photons after the "motherphoton" hits the BBO-crystal, not 2 (single and idle X 1).

So, instead of having 1 motherphoton, which get separated into 2 new and entangled with half the oiginal frequence, we get 4 with 1/4 og the original frequence?

Note: I am aware of the fact that this would not be the case if we track the idle photons route, because then the wavefunction fails. My question is only relevant when trying to understand what happens as we get a interference pattern fom the idle photon.

I can't seem to find any answar to this, please help.

Regards from DK.