Undergrad Delayed Choice / Quantum Eraser Experiment Question?

[Phillane]

Hello,

Disclaimer:
I have read other posts and understand it is important to reference ‘sources’ and that popular science articles / videos can be a source of annoyance. However, I am struggling to:
A. Find an answer to my question, and/or
B. Understand if my question is even valid.
I hope someone can either provide and answer or point me in the right direction.

I recently watch on YouTube a video regarding the Delayed Choice Quantum Eraser experiment presented by PBS Space Time. The video was not particularly long so I expect excluded a lot of technical detail.

The video seemed to infer that despite the detetection of which slit the photon went through (via the 2nd entangled photon hitting the detector) occurring after the first entangled proton is detected, the absence of an interference patterned still ocrrued, and that therefore the ‘late’ detection somehow retroactively affected the first entangle proton or sent information into the past. (Those were the terms used in the video).

I suspect there are multiple theories for this and the presentation was made in a way to be more ‘weird’ than is actually the case.

My question is however (and i can't find any answer to this) , the video and explanation were presented from the basis as us as the observer and in our frame of reference, with one event occurring after the other. As photons travel at the speed of light, is the concept of time in this scenario irrelevant. From the point of view of the entangled photons would the detection of 2nd photon (and collapse of quantum wave) and detection of 1st photon happen at the same time? And so therefore this is no retroactive action or information into the past.?

If this question is garbage - tell me to move on :)

Many thanks
Phil

 

[PeterDonis]

I recently watch on YouTube a video

YouTube videos are not generally good sources if you are trying to actually learn the physics. You need to look at textbooks or peer-reviewed papers.

this is no retroactive action or information into the past.?

That is correct, but it's a general answer. Specific delayed choice experiments can vary in how they are set up, so exactly how you would demonstrate that this answer is correct can vary from experiment to experiment.

 

[Phillane]

YouTube videos are not generally good sources if you are trying to actually learn the physics. You need to look at textbooks or peer-reviewed papers.

Understood - however I suffered a stroke last year and am left with cognitive issues, which particularly affect comprehension of written text and reading more than a page or so of information.

I am generally trying to keep some sort of learning going on topics that interest me, even if this is limited

That is correct, but it's a general answer. Specific delayed choice experiments can vary in how they are set up, so exactly how you would demonstrate that this answer is correct can vary from experiment to experiment.

OK, thanks. Understood

 

[PeterDonis]

I suffered a stroke last year and am left with cognitive issues, which particularly affect comprehension of written text and reading more than a page or so of information.

I'm sorry to hear that. If videos are a better medium for you, there are videos online of Susskind giving lectures on various topics; those might be better since they're intended as teaching videos, which the PBS SpaceTime episodes are not.

 

[DrChinese]

My question is however (and i can't find any answer to this) , the video and explanation were presented from the basis as us as the observer and in our frame of reference, with one event occurring after the other. As photons travel at the speed of light, is the concept of time in this scenario irrelevant. From the point of view of the entangled photons would the detection of 2nd photon (and collapse of quantum wave) and detection of 1st photon happen at the same time?

The quantum statistics do not really depend on time. Regardless of the speed c of a photon - or any other particle for that matter: the order of observations is not important in making predictions. Accordingly, relativity is not really a factor, because there is no time element to adjust. Experiments are routinely performed where observation or event order is forced to be (A then B) or (B then A). No difference either way.

 

[Johan0001]

"The quantum statistics do not really depend on time"

This I agree with.
What mystifies me is that both observations A and B depend on the other's result. Taking one apparently sets the other when observed.
And the observations are separated in time, with no preferred order.
So when do the correlations manifest , or were they always there to begin with, somehow mapped out without explanation.

Regards