
An Overview of Bayesian Inference (2019) - luu
https://jaydaigle.net/blog/overview-of-bayesian-inference/
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ur-whale
Slightly OT, but I wonder if anyone in the know could shed a light on where
Baye's theorem is applied (if anywhere) in quantum mechanics?

In particular, has anyone tries to apply the bayesian framework to the whole
"the wave collapses upon measurement" shebang?

~~~
deepnet
"Quantum Bayesianism, or QBism as Fuchs now calls it, solves many of quantum
theory’s deepest mysteries. Take, for instance, the infamous “collapse of the
wave function,” wherein the quantum system inexplicably transitions from
multiple simultaneous states to a single actuality. According to QBism, the
wave function’s “collapse” is simply the observer updating his or her beliefs
after making a measurement."

[https://www.quantamagazine.org/quantum-bayesianism-
explained...](https://www.quantamagazine.org/quantum-bayesianism-explained-by-
its-founder-20150604/)

~~~
kgwgk
It's not that simple. When a measurement is done on a pure state (where the
knowledge of the state is already as good as it gets) the observers are not
just updating their beliefs, they are changing the system. On the other
extreme, in some cases one may have measurements that improve our (imperfect)
knowledge of the physical state without disturbing it.

"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](https://www.perimeterinstitute.ca/personal/cfuchs/Oviedo.pdf)

