Sabine Hossenfelder
5 HN recommenders · recommended in 5 months, 2021–2026
12:51 · 718K views · Oct 30, 2021
Sabine Hossenfelder explains the delayed choice quantum eraser and argues it does not rewrite the past, as popular accounts claim. She walks through what the experiment actually shows.
HN recommends it as a clear debunking of the retrocausality interpretation of the quantum eraser.
6 comments from Hacker News
This is a very interesting, novel take on explaining the delayed choice quantum eraser. I think I can summarize it as follows: The signal photon hits the screen, which is a measurement. The entangled idler's wave function is thereby constrained by that measurement, influencing the probabilities of later detecting it at each of the D1-4 detectors. It's not that the fate/erasing of the idler changes the already committed path(s) of the signal. It's that the measurement of the signal constrains the subsequent detection of the idler. Two other high quality discussions of eraser experiments are by Sean Caroll [0] and Sabine Hossenfelder [1]. Like the OP, both Sabine and Sean demystify/debunk these experiments. These three discussions all use different language to explain the outcome, which is clearly predicted by the QM math. Sean's article includes the gist of the math. [0] [LINK] [1] this video
I think Sabine explained this social effect few years ago. I know she's a little controversial, but the key thing in the video (as opposed to all other videos about DSE on the internet) was that you don't get "two clusters" actually. They are both statistical parts of a single [non-]interference pattern. "||" is a lie. I'm not in a physics rebel camp and don't prefer Sabine either, but after that I sort of lost trust in the interpretations that can't even get the resulting picture right. I even suspect that showing dumbed results amplifies "wow" effect and monetizes better. this video This is the video if you're interested. Again, I'm no physicist and don't know if explanations are legit or statistically correct. But that little || trick that all other popsci videos play on you, that's a true concern.
PBS Spacetime did an interesting video on DCQE, but it tripped me up trying to fully understand what was happening: [LINK] ... Later Sabine Hossenfelder did a video debunking the proposition that DCQE somehow showed that the past was being rewritten. this video And Matt from PBS Spacetime acknowledged she was right in this respectful comment: > Sabine, this is amazing. You are, as usual, 100% right. The delayed choice quantum eraser is a prime example of over-mystification of quantum mechanics, even WITHIN the field of quantum mechanics! I (Matt) was guilty of embracing the quantum woo in that episode 5 years ago. Since then I've obsessed over this family of experiments and my thinking shifted quite a bit.
>The delayed-choice quantum eraser wasn’t carried out experimentally until 1999, so I think it’s a bit misleading to say this is what makes the double-slit experiment (first carried out with matter in 1927) so weird. I think Sabine is right, the weirdest thing in the quantum eraser experiment is still the FTL update of the wavefunction. She has a nice video on delayed-choice quantum eraser: this video
Ok, that's definitely not what OP said. Of course the particle still can interfere with itself after the slit, it's just that when the measurement is made, the pattern of two waves interfering gets much weaker/non-existent. Also, the experiment you are alluding to does not say what you think it says. Perhaps you will be interested on another video from Sabine. this video