If the single photon simultaneously bounces off the partially-silvered mirror and goes through it, you're not going to get an answer to a binary question from this experimental set-up.
So after every quantum experiment you get N copies of the world, one in which outcome A has happened, one in which B has happened, one in which outcome C has happened etc, and each of these evolves divergently from there on. Of course, there are trillions of trillions of trillions of "quantum experiments" happening in our immediate surrounding every second, so any one experiment in particular is not that important, but it helps to isolate.
So, instead of taking a decision, you use the app to rest easy that somewhere out there in the universal wave function, there is a copy of you that has taken the opposite decision.
IDK, I guess the whole speed of light thing is really silly too in a way, but that's provably true.
This just feels really nuts. I guess it's like... where do all of these universes live? I get that our universe expands into whatever, but that seems trivial compared to a theory where every single quantum action leads to a new universe.
If you think Max Tegmark is right, then the universe is just mathematics and space itself is a mathematical structure. Is there a limit on how many mathematical structures can exist?