Question about delayed choice quantum eraser

[ijdavis]

Same number of photons yes. But the emergent distribution of where the photons at D0 strike a screen will if it cannot be determined which slit these photons passed through be to produce a diffraction pattern at D0, while to not produce this diffraction pattern if the red and blue paths differ as to where they arrive consequent of it then being possible to say which slit the photons went through. Or am I misunderstanding how the diffraction pattern is to be observed/derived when it exists at D0.

 

[DrChinese]

Same number of photons yes. But the emergent distribution of where the photons at D0 strike a screen will if it cannot be determined which slit these photons passed through be to produce a diffraction pattern at D0, while to not produce this diffraction pattern if the red and blue paths differ as to where they arrive consequent of it then being possible to say which slit the photons went through. Or am I misunderstanding how the diffraction pattern is to be observed/derived when it exists at D0.

You can see from the diagram that all D0 photons are focused by a lens to a single point. Therefore, there is no pattern to observe. Again, nothing changes at D0 based on any action on the other side.

And if you remove that lens, I am not really sure what you would expect to see either other than maybe a couple of blobs. One for the red stream and one for the blue stream.

 

[San K]

However, if one can force all entangled twins to arrive at D3 or D4 it seems one can force a result at D0, which no longer requires any correlation to be performed.

D0-D3 (alone) forms an interference pattern.
D0-D4 (alone) forms an interference pattern.

However D0 contains both D3 and D4.

The two patterns overlap such that the crest of one aligns with the trough of the other.

Thus no interference pattern is seen, only a "blob" is seen.

 

[kaplan]

I do exactly the same thing with MWI
It is my main - if not sole - justification for considering MWI.

I don't understand that attitude. If the MWI makes it easier and conceptually simpler to understand QM - and it does - then why not accept it as the best interpretation of QM?