>The most well known example of a quantum thought experiment, the Schrödinger cat, is about quantum mechanics (seemingly) not working at macroscopic scale (only last year was there a good theory explanation of the paradox https://pirsa.org/20010099 )
It's like I'm reading a comment from a strange alternate universe where decoherence was never discovered and quantum mechanics hadn't progressed past the 1930s philosophically. How can you know about so many proposed experiments without also knowing why "quantum mechanics stops working at macroscopic scales" is absurd? Is there really a group of scientists that think that? Can we find some missionaries to translate their native language and reach them?
I gave you a lecture from last year from Scott Aaronson, one of the most respected Quantum Information theorist in the world. Are you really claiming that he is unaware of the philosophical progress since the 30s? I also happen to work in this scientific field professionally, although I am not a luminary like Aaronson. I do consider these questions not yet well answered, so this is a "yes" to your rather rude question about whether scientists are interested in this.
Also, I am truly confused, what do you mean by "decoherence" being discovered? Being able to perform a partial trace and use a density matrix (and call it "decoherence"), does not really help with answering these questions.
The explanation for Schrodinger's cat is that in any practical box, you will end up as a part of the cat's state almost instantly. There will be one state where you're standing outside of a box with a living cat, and another where you're standing outside of a box with a dead cat. It's up to you to assign metaphysical status to those states, but the dynamics are clearly predicted.
I think you may be misapprehending the meaning of Aaronson's talk. He is saying that proving that a specific cat was in a superposition would be just as hard as changing its state from dead to alive, but that does not preclude the possibility of proving that several cats are in a superposition by observing the statistical properties of an ensemble of measurements. If that talk explained why Schrodinger's cat doesn't happen in our daily lives, it would have to address why we can't detect cat superposition probabilistically, like the way we detect particle superposition in most experiments (the interference pattern of the dual comb experiment only appears when there are a lot of measurements).
You are using vague ill defined words that just end up confounding topics in a meaningless way. For one, Schrodinger's cat premise has absolutely nothing to do with superpositions of multiple cats. There is no such thing as superpositions of multiple objects, especially if they are distinguishable like cats. Superposition are over different possible states of a single system not over multiple copies of a system. You can not interfere two cats together. The most charitable interpretation of what you are saying is some abuse of the language used to describe indistinguishable particles or some statement in second quantization, but that also has nothing to do with Schrödinger's cat.
>There is no such thing as superpositions of multiple objects, especially if they are distinguishable like cats.
Several superpositions of several cats makes an ensemble of experiments over which it would not be as difficult to detect entanglement as it would be in the case of one cat, which is the case that Aaronson describes.
Just write the ket describing that state and specify over what Hilbert state it is. At best, "superposition" does not mean what you are using that word for. It just sounds like nonsense right now.
Take several of these and you can collect data across several expeirments that shows they're in a superposition, but if you only have one, Aaronson's argument applies.
It's like I'm reading a comment from a strange alternate universe where decoherence was never discovered and quantum mechanics hadn't progressed past the 1930s philosophically. How can you know about so many proposed experiments without also knowing why "quantum mechanics stops working at macroscopic scales" is absurd? Is there really a group of scientists that think that? Can we find some missionaries to translate their native language and reach them?