I believe this hypothesis assumes some sort of metaphysical property to consciousness. Also, Permutation City did it first (consider this a book recommendation).

Disclaimer: I'm not a physicist. I'm just some random internet dude who likes learning things. My understanding is that a single photon wouldn't count as an observer. It doesn't even experience time (from the point of view of the photon, admission and absorption are simultaneous). Now if that photon is entangled with another photon, that can then be considered an observer. Someone please correct me if this is not accurate.

(Disclaimer: physics undergrad.) I honestly wish we could get away from the word "observer" - it's more or less a historical accident and it probably confuses more than it helps.

Talking about coherence and [decoherence](https://en.wikipedia.org/wiki/Quantum_decoherence) is IMO a lot more intuitive. Always keep in mind, if you're reading about quantum physics and there's anything in there about consciousness or subjective experience or whatever, then you're either reading something very fringe, or you've misunderstood what the paper is saying. Quantum physics is weird, but it's not that weird.

As in "an observer which/who requires causality and cannot exist in superposition". Whatever that is. Is causality a product of at least a minimal level of awareness? (We won't be able to tell, as exploring the concept of causality already presupposes awareness.)