Two particle interference (entanglement)

[4everlonging]

Homework Statement

A source emits pairs of particles "back to back", 50% into directions a1 and b1, 50 % into directions a2 and b2, where the choice between a1+b1 and a2+b2 is fundamentally undetermined.

Insert Diagram A

suppose that directions a1 and a2 are combined on a 50/50 beam splitter(equal path lengths)

Insert Diagram B

what percentage of the particles emitted to the left will be detected in each detector?

 

[4everlonging]

what?