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.
For me, the weird thing about the double-slit experiment for matter is that the excitations of the detector are discrete, i.e. we see individual particles arriving at the detector, as expected under the classical model of matter behaving like particles.
It’s only when we send many particles over time, that we can tell that we’ve been sampling from a distribution given by the interfering wave-functions.
This suggests that the particle is interfering with itself, thus behaving like a wave, but since we only detect each particle in a single place, it’s still behaving like a particle in some sense.
This is very different from the classical wave phenomena seen when we do the double-slit experiment in a water tank, where there is constant interference across the whole axis the whole time (there is no particle-like behaviour at all).
gtowey•7h ago
There is an alternative explanation for this behavior which says that there is a wave and a particle at all times. The wave and particle interact with each other and influence how they move and propogate. It says that we see the interference pattern because the wave does indeed travel through both slits, but the particle only travels through one. It was dismissed by physicists led mainly by Neils Bohr because the alternative theory didn't seem to handle some edge cases gracefully, but new techniques have made this again an interesting area of exploration. Personally, I hope it's true because it means that quantum physics will have an explanation that feels intuitive in the sense that it will follow rules that are similar to physical phenomenon we are familiar with at the macro scale.
>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.
denotational•9h ago
For me, the weird thing about the double-slit experiment for matter is that the excitations of the detector are discrete, i.e. we see individual particles arriving at the detector, as expected under the classical model of matter behaving like particles.
It’s only when we send many particles over time, that we can tell that we’ve been sampling from a distribution given by the interfering wave-functions.
This suggests that the particle is interfering with itself, thus behaving like a wave, but since we only detect each particle in a single place, it’s still behaving like a particle in some sense.
This is very different from the classical wave phenomena seen when we do the double-slit experiment in a water tank, where there is constant interference across the whole axis the whole time (there is no particle-like behaviour at all).
gtowey•7h ago
https://en.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory
TxFkdZ•6h ago
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: https://www.youtube.com/watch?v=RQv5CVELG3U