[nonbel]

Sounds like the wave model describes the statistical properties of a population of photons.

Eg, a coin flip is deterministic if you know all the forces involved (airflow, force of flip, exact distribution of mass of the coin, etc). But since we are usually ignorant of all that, instead we model it as a bernoulli trial.

[kgwgk]

But that’s not what qbism is about: a wave function (pure state) doesn’t represent ignorance about a true underlying physical state, it’s a maximally sharp state of belief.

[nonbel]

> Regarding quantum states as degrees of belief implies that the event of a quantum state changing when a measurement occurs—the "collapse of the wave function"—is simply the agent updating her beliefs in response to a new experience. https://en.m.wikipedia.org/wiki/Quantum_Bayesianism

You could be right, That is what this sounds like to me though. According to the model there is a 50% chance the coin will land on heads, until you flip it.

[kgwgk]

For a pure state a measurement doesn’t improve our knowledge about the state of the physical system, it changes it (and we get information about the new state). The Bayesian updating applies to mixed states, where there exists “classical” uncertainty while for a pure state the uncertainty is purely “quantum”.

"Quantum measurement is nothing more, and nothing less, than a refinement and a readjustment of one’s initial state of belief. [...] Let us look at two limiting cases of efficient measurements. In the first, we imagine an observer whose initial belief structure ρ = |ψ⟩⟨ψ| is a maximally sharp state of belief. By this account, no measurement whatsoever can refine it. [...] The only state change that can come about from a measurement must be purely of the mental-readjustment sort: We learn nothing new; we just change what we can predict as a consequence of the side effects of our experimental intervention. That is to say, there is a sense in which the measurement is solely disturbance."

https://www.perimeterinstitute.ca/personal/cfuchs/Oviedo.pdf

[nonbel]

Thanks, not what I was thinking it sounds like.