Why isn’t the fact you’re saying “A quantum state is a wave-function that evolves according to the Schrodinger equation; the rest is commentary” makes you simply a many-worlder (albeit in denial….)?No, this is a straw man attack on Copenhagen/QBism.
Don’t you agree that this is the claim to fame of the Everettians? All other interpretations suggest that something is missing in the theory (whether the wave-functions are an incomplete description of the physical reality, or the Schrodinger equation is an incomplete description of the way they’re evolving).
If I’m just an Everettian in denial, then by the same standard, almost every informed person nowadays is likewise just an Everettian in denial! Besides Penrose and GRW, I don’t know anyone today who thinks of “collapse” as an actual physical thing. Certainly not the Copenhagenists or QBists! The way they’d put it is that for them, quantum states are personal, “collapse” is just Bayesian updating, and there’s no such thing as the “quantum state of the universe.” The way I’d put it is that, if you force them (kicking and screaming) to write down a quantum state that includes human beings, they’ll simply deny that the fire of experience gets breathed into more than one of its branches.
The Copenhagenists do not believe that the wave function is a actual physical thing. It is a mathematical tool for predicting measurements.
To the extent that it is the best tool we have, it certainly does collapse. The collapse is real. Saying that the collapse is real is another way of saying that a measurement on an entangled state yields a single value.
They also believe that quantum mechanics can be used for everything, including stars, human beings, and the universe at large. There is no such notion of breathing fire of experience into a wave function. Aaronson just made that up.
The many-worlds/Everett folks would rather say that the measurement causes a branch of the wave function to become irrelevant. Okay, that is another way of expressing the collapse. The difference is that the many-worlders go a step further and say that the irrelevant branches continue on in a parallel universe. That is the kooky part that is the heart of the theory.
Excellent passages these, but, IMO...
>> "The Copenhagenists do not believe that the wave function is a actual physical thing. It is a mathematical tool for predicting measurements."
IMO, replace "Copenhagenists" by MSQM (mainstream QM).
>> "To the extent that it is the best tool we have, it certainly does collapse. The collapse is real. Saying that the collapse is real is another way of saying that a measurement on an entangled state yields a single value."
Correct, but IMO, replace "a single value" by "a tuple of values (defining a single point) in the configuration space".
Also, BTW, IMO, QBism is a misguided way of looking at it.