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This is similar: Interference pattern in delayed choice quantum eraser

However, it appears to misunderstand the notion of the detectors D3,D4 providing path information and affecting the results at D0.

My question is: When there is no path information being provided, why does the experiment still call for moving D0?

I understand that by moving D0 we can modify the arrival time of the idler photon.

I don't understand, why when there is no path information being provided at D3,D4 do we need to still move D0 in order to obtain an interference pattern.

"During an experiment, detector D0 is scanned along its x axis, its motions controlled by a step motor. A plot of "signal" photon counts detected by D0 versus x can be examined to discover whether the cumulative signal forms an interference pattern. "

Source: https://en.wikipedia.org/wiki/Delayed-choice_quantum_eraser

Why doesn't an interference pattern occur at a stationary D0, when there is no path information being provided at D3,D4?

AlphaCentauri
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  • " I don't understand, why when there is no path information being provided at D3,D4 do we need to still move D0 in order to obtain an interference pattern". D3, D4 are detectors that only provide path info. Yes you don't have to scan with D0 but you won't get the complete picture. Note D0 is scanned to get an image. ... it is not a CCD (camera), the image is built up over time. D0 is not scanned for the purposes of changing idler time .... idler time is a one time change they make to the apparatus, i.e. arm length. – PhysicsDave Nov 05 '23 at 18:54
  • @PhysicsDave So D0 is moved to get a complete picture. D0 can only detect single photons and needs to also record the X position for each pixel, and do this statistically over time? Is this merely a technical implementation detail? Another way to implement this would be with a stationary D0 that is a CCD that can detect individual photons at multiple locations (over time) on a stationary surface? – AlphaCentauri Nov 06 '23 at 00:25
  • D0 is effectively a 1 pixel detector ..... and all the detections are done in coincidence with the others because there are a lot of photons flying around and few choose the paths they need for the experiment. Also the eraser experiment has mostly been "debunked" in terms of faster than light communications. – PhysicsDave Nov 06 '23 at 00:34
  • A CCD wouldn't be fast enough for coincidence detection. – PhysicsDave Nov 06 '23 at 00:36

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