Some Tenets of QBism

Lecture by Christopher A. Fuchs given at Workshop on Participatory Realism, Stellenbosch Institute for Advanced Study (STIAS), Stellenbosch, South Africa, 6 June 2017. Filming by Bill Thisdell; editing by Blake C. Stacey and Bill Thisdell. This work was supported in part by a Foundational Questions Institute (FQXi) mini-grant “Why the Quantum? A Video Series” (grant FQXi-MGB-1624), a donor advised fund at the Silicon Valley Community Foundation.

[erawanpencil]

So a flipping coin is in itself objective reality, but when I use the Born Rule to say its landing probability is 50/50 heads/tails, that probability isn't a law of nature but just me subjectively telling myself how to prepare?

[norabelrose]

35:00 probability one just means “almost surely, ” you can still have non-empty measure-zero sets of possible outcomes incompatible with the event you’re saying is probability one

[AndrewBrownK]

Cheat Sheet of QBism Tenets:

1. The Born Rule - the foundation of what quantum theory means for QBism - is a normative statement. It is about the decision-making behavior any individual agent should strive for; it is not a descriptive "law of nature" in the usual sense.

2. All probabilities, including all quantum probabilities, are so subjective they never tell nature what to do. This includes probability-1 assignments. Quantum states thus have no "ontic hold" on the world.

3. Quantum measurement outcomes just are personal experiences for the agent gambling upon them. Particularly, quantum measurement outcomes are *not, * to paraphrase Bohr, instances of "irreversible amplification in devices whose design is communicable in common language suitably refined by the terminology of classical physics."

4. A measurement apparatus is conceptually an extension of the agent. It should be considered analogous to a sense organ or prosthetic limb - simultaneously a tool and a part of the individual.

And lastly, what is the value? According to Will Durant:

The value of this conception of the universe, lies in this, that where there are cross-currents and warring forces our own strength and will may count and help decide the issue; it is a world where nothing is irrevocably settled, and all action matters. A monistic world is for us a dead world; in such a universe we carry out, willy-nilly, the parts assigned to us by an omnipotent deity or a primeval nebula; and not all our tears can wipe out one word of the eternal script. In a finished universe individuality is a delusion; 'in reality', the monist assures us, we are all bits of one mosaic substance. But in an unfinished world we can write some lines of the parts we play, and our choices mould in some measure the future in which we have to live. In such a world we can be free; it is a world of chance, and not of fate; everything is "not quite"; and what we are or do may alter everything.

[ming-fengho]

Great talk! I was trying to read some QBism articles recently, and this talk really gives intuition about the relation between Bayesian and QM. Wondering if I can use QBism to write my quantum mechanics homework.

[patinho]

Quantum states have no notice hold on the world. Love it. Indeed: everything is choosing its actions and states!

[capitanmission]

hi chris, Im JM Jones volonte, I like the distilled 2018 style presentation! Im doing my job spreading Qbism in the spanish speaking world

[ASLUHLUHC]

You've taken the words out of my thoughts

[david_porthouse]

I am interested in including a random number generator in a computer simulation of quantum mechanics. Can QBism provide any guidance?

[ashleyjohnston]

I'm hooked. I've been looking for this. My only concern so far is that you seem to be assuming non-determinism. Cheers.

[yacc]

4:32 Wikipedia, like writing on water