Last night I had a super nerdy dream.
My parents' cat is not allowed outside. Usually she's not just gunning to go outside either, being, as cats go, a fairly timid creature, but every now and then she does look longingly out the window. I know it's against their nature and all that, take that rule up with my mom if you think locking her inside is cruel. At least the local bird, chipmunk, vole, mouse, squirrel population can be thankful for it.
In the dream, a door to a house that was definitely not my parents' house but nevermind that, opened, and my parents' cat rushed to it, eager to get out. I tried to shut the door quickly, but the fuzzy dream events occurred in such a way that I could not tell if I was keeping the cat in or letting it slip out, my dream-brain ignoring the entirely-too-classical possibility that I ws shutting the door on the cat.
In the end, it seemed like I had kept the cat inside. Yet as I watched, the cat walked through the solid door, and suddenly there were two cats, one inside, and one outside.
And in the dream I exclaimed, "She just tunneled through the door! She bifurcated! Now there's two of her. Mom, what do I do about it?"
Dream mom was unsure, looking to the physics major for answers. "Don't you know how to fix it?" she asked.
"I don't know," I answered. "I don't know how to put her wave-function back together." But I went outside and scooped outside-cat up, and brought her back in, next to inside-cat, hoping that, in the language of quantum mechanics, if they were together it would induce their wave-function to be an eigenstate of inside-cat only, rather than being a superposition of the eigenstates of inside-cat and outside-cat both.
Now, the quantum concepts I'm referring to are not exactly right, obviously because cats are well outside of the limit where quantum behavior comes into effect. Also, the phenomenon in the dream, wheras something that, faced with two possibilities, behaves as if it does both if you are not able to determine what happened, goes away as soon as you can determine it (although yes, it would not actually happen with a cat.)
If I couldn't tell what happened and so suddenly I saw two cats, maybe some other sense, like touch or sound, would have broken the time of no-information, so as soon as I picked up outside cat, inside cat should have gone away, or rather, the cat wave-function would stop being a superposition of outside cat and inside cat and start being just outside cat again.
Then again, it didn't exactly occur that way: I couldn't tell what happened while I was closing the door but afterwards I saw inside cat "tunnel" through the it, which is an incredibly improbable occurrence, but if it did happen would not have caused the two-cat problem. So my brain was just mixing up scattered and sensationalized quantum concepts.
I did do a lab experiment once which verified the photon-faced-with-two-options-behaves-as-if-it-takes-both-if-you-can't-tell phenomenon, but in general these concepts are all subtle and mathematical and obviously non-nonsensical when applied to our world.
But cats are pretty magical, after all.