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.