Q: What if the particles in the double slit experiment were conscious? Could you ask them which slit they went through afterwards?
The photon’s polarization is being used here as a “pointer state”, and it’s a good way to talk about “memory”. Finally, Wigner’s Friend can alert the outside world that a measurement has been successfully done, without reporting the result. Regardless of the result, Wigner’s Friend still did the measurment accurately and only saw the one result. We can feel confident that if we feed in a photon, then Wigner’s Friend will eat a superposition of flavors . However, if you asked Wigner’s Friend what he experienced, he’d tell you an answer; either vanilla or chocolate, but not both.