[ExI] Quantum Bayesianism (QBism)

[Stuart LaForge]

On 2023-09-08 03:33, BillK via extropy-chat wrote:

> I asked AI to summarize and explain QBism:
> 
> QBism, also known as Quantum Bayesianism, is a philosophical
> interpretation of quantum mechanics that combines elements of
> subjective probability and Bayesian reasoning. It was developed by
> physicist Christopher Fuchs and his colleagues in the early 2000s as a
> response to the long-standing interpretational issues and paradoxes in
> quantum theory.

There are no paradoxes that I am aware of in MWI. All the 
physics-breaking paradoxes stem from collapse-based theories. MWI is 
Lorentz-invariant and conforms to both special and general relativity. 
No collapse theory can claim that. MWI, like special relativity, works 
whether there is an observer in a particular inertial reference frame or 
not.

> At its core, QBism asserts that quantum mechanics is fundamentally
> about an agent's personal beliefs or degrees of belief rather than
> objective reality. It emphasizes the role of the observer and their
> subjective experiences in understanding quantum phenomena. According
> to QBism, the wave function, which describes the state of a quantum
> system, represents an agent's personal probabilities or expectations
> for different measurement outcomes.

At the molecular-level, biological evolution is a quantum phenomenon. 
Probabilistic quantum wavefunctions dictate whether a photon of ionizing 
radiation will strike one particular nucleotide in DNA and mutate it 
instead of another as  well as where the breakpoints for 
recombination/repair will occur, and numerous other mechanisms of 
genetic variation. As such, this suggests that in order for the FIRST 
life-form to have evolved, there needed to be an observer watching it. 
This is tantamount to simulation theory, intelligent design, or 
creationism which all require an explanation as to where the programmer, 
creator, or initial observer came from.

There are only two possibilities that answer the question, "Where did 
God come from?" The first is that He is infinite and always existed 
beyond space and time. The second is that he is a finite being running a 
simulation of sorts and was himself created or "observed" into existence 
by a superior being living in a larger, more fundamental reality. But, 
if that is the case, then where did this uberGott in basal reality come 
from?

The answer to this can logically only be either an infinite supreme god 
or an infinite series of nested finite gods that have created successive 
gods all the way down. Like matryoshka dolls that go on forever. But 
therein lies the rub, because whichever you choose, you must admit the 
metaphysical existence of INFINITY.

And infinity is all you ever really needed in the first place. God, all 
gods, become superfluous once you accept multiverse theory, because 
within the universal wave function all gods exist somewhere. That is to 
say that there are likely Everett branches out there where some 
observers for whom wavefunction collapse does occur to save RAM and CPU 
cycles.

> 
> In QBism, probabilities are understood as subjective degrees of belief
> rather than objective frequencies or propensities. These probabilities
> are updated using Bayesian inference, a mathematical framework for
> updating beliefs based on new evidence. The agent's beliefs are
> represented by a probability distribution over possible measurement
> outcomes, and this distribution is updated using Bayes' theorem after
> each measurement.

All probabilities, or just quantum ones? After a coin flip, does "tails" 
exist when you are observing "heads"? Many worlds says everything that 
can happen, must happen somewhere. That is quantum unitarity. 
Counterfactual observables are observed by someone somewhere.

> One key aspect of QBism is its rejection of the idea that quantum
> systems have definite properties before they are measured. Instead, it
> argues that these properties only exist in relation to an observer's
> measurements and their subjective beliefs. This view is often referred
> to as "participatory realism," as it suggests that reality is created
> through the interaction between the observer and the observed system.

Participatory realism is isomorphic to living in a videogame or 
simulation where computational resources are saved by rendering reality 
only as needed to serve the player or observer.

> Another important concept in QBism is the notion of "quantum states as
> personalist Bayesian agents." According to this idea, quantum systems
> can be thought of as agents that update their own beliefs based on
> their interactions with other systems. This perspective allows for a
> more intuitive understanding of entanglement and non-locality in
> quantum mechanics.

So electrons have beliefs in QBism? Are photons watching us into 
existence? Do muons have souls? QBism is starting to sound like good 
old-fashioned animism.

> 
> QBism also addresses the long-standing debate between wave-particle
> duality and the collapse of the wave function. It suggests that these
> concepts are not fundamental but rather emerge from an agent's
> interactions with quantum systems. The wave function is seen as a tool
> for making predictions about measurement outcomes, rather than a
> physical entity.

The wavefunction cannot be observed, yet it nonetheless necessarily 
exists. That makes it more than a merely physical entity, but instead a 
metaphysical entity. This means that MWI is the first experimentally 
tested and mathematically rigorous metaphysical theory in existence and 
Hugh Everett was the first true metaphysicist.

> Overall, QBism offers a new perspective on the interpretation of
> quantum mechanics that places the observer and their subjective
> beliefs at the center of the theory. It provides a framework for
> understanding quantum phenomena in terms of personal probabilities and
> Bayesian reasoning, challenging traditional notions of objective
> reality.

Yes. It is also violates the Copernican principle, general relativity, 
and is equivalent to intelligent design.

> So, Many Worlds Interpretation is not required with QBism.
> BillK

Yes, MWI is not required with QBism, but because it is more general, MWI 
allows for QBism. In fact, it would predict that there are many 
universes out there where simulations are in operation and wavefunction 
collapse and QBism are the descriptor of the wavefunction in those 
simulations. It is not so much that one must choose between either 
finite turtles all the way down or the infinite multiverse. But that 
even if it is turtles all the way down, the turtle on the bottom is 
standing on an Everett branch.

Stuart LaForge