Why can't we test observer memory directly using the double-slit experiment?

1 kylebenzle 1 5/13/2025, 2:51:27 PM
If we use a double-slit experiment with a which-path detector, and have an observer try to remember (or forget) which slit each photon passed through, why can't we use the resulting pattern—interference or not—as a readout of the observer’s memory state?

If no one remembers the which-path info, we expect interference. If someone does remember, the pattern should collapse to two bands. Why hasn't this been tested as a method to probe the interaction between human memory and quantum measurement? Feels related to Wigner’s friend, but focused on the memory-retention threshold.

Is this experimentally viable?

Comments (1)

david927 · 12h ago
My understanding is that the wave function will collapse if information can be retrieved, so the moment it can be known which slit it goes through, it's already over.

I also have a fun QM experiment idea but I could be wildly misinformed:

You make two experiments, one where you fire polarized photons at a screen and one where you fire non-polarized photons. You come back some time later (irrelevant but who cares), and decide using a cosmic radiation detector (radiation still coming to us from the big bang, so truly non-deterministic) which screen to choose. You fire a regular photon and the two slits. My understanding is that if the polarized screen is chosen, the photon will come through as a particle and if not, as a wave.