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I am going into quantum physics the past days specifically the dual slit because it boggles my mind.

You can find the Wikipedia here https://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser

And this is the picture:

https://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser#/media/File:Kim_EtAl_Quantum_Eraser.svg

Now it is said that D3 and D4 never have an interference pattern because we know the path those photons took. It is also said that D1 and D2 always have an interference pattern because we can't know the path those photons took because of the randomness in the green silver plates.

But here it comes (my thinking): The distance the photon travels to D1 is never the same as the distance to D2. This is because you can never put 2 objects at an 100% exact distance from eachother. There is always the slightest of differences. This is also the case for Mb to BSc and Ma to BSc and PS to Ma and PS to Mb and so on... all these paths have distances that are different from eachother. I can measure the exact distance the photon has travelled by time measurement and speed of light. If I then compare that distance to the experiment layout distances I can puzzle this in and find the exact path. Right? So why is it still an interference pattern if we could theoretically determine its path?

What is wrong in my thinking :(

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# I I can determine the photon path in delayed erasure

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