Brian Green's Beam Splitter Experiments

[moving finger]

so what's the problem?

you answered it - the BS (ie semi-transparent mirror) is spatially asymmetric, and this results in the fact that idler photons going to D1 are phase-shifted with respect to those going to D2 - which in turn explains why there is no structure in the raw D0 data.

Is there such a thing as a symmetric beamsplitter - one that does NOT result in a 180 degree phase shift? If there were, and we were to use it, this would imply there should be structure in the D0 data? But this would also open the door to paradoxes - so maybe a symmetric beamsplitter (one that does not cause a phase shift) is physically impossible.

Best Regards