Part 6 - Rüdiger Schack: 'QBism and normative probability in quantum mechanics'

What course of action should I take? This is the question that decision theory is designed to answer. An agent's rational decision-making is constrained by the rules of the probability calculus which thus plays a normative role in decision theory. According to QBism, the quantum formalism is a tool that any agent can use to answer the very same question: What course of action should I take? In the QBist approach, probabilities in quantum mechanics guide an agent's decision-making, and the Born rule functions as a further normative constraint on the agent's probability assignments, in addition to the constraints imposed by probability theory. In this talk I give a simple introduction to the decision-theoretic approach to probability and explain how quantum mechanics itself provides compelling arguments for the QBist view.

Rüdiger Schack is professor for mathematics at the University of London.

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1. Lead 00:00:00
2. History of QBism 00:00:08
3. Personalist probability. Dutch book coherence 00:05:27
4. Frequencies and repeated trials 00:11:10
5. Probabilities in QBism 00:18:22
6. Quantum teleportation 00:25:41

[alexanderabrashev]

Can't get my head around this idea.. wow

[Achrononmaster]

@1:20 you are therefore stating "an agent's personal beliefs" could "derive from pure quantum states". This is one dopey mix-up of concepts. Pure quantum states relate to a theory of physics. Sure, "people" came up with QM and this theory informs our beliefs, but the physical reality we perceive is not the source of our beliefs. Our beliefs are a category of mental qualia, and physics has absolutely no clue where those qualia come from. They are not brain states. They are something else, and it is not physics. So they cannot derive from quantum mechanics (which is physics). Unless you are prepared to do violence to the definition of the word "physics", but then you are causing a mess of mixing of domains of scientific modelling, which is unhealthy in my view (especially for clean physics pedagogy --- and I am by no means an establishment guy, I do however value good pedagogy in learning, even if the student has to find it for themselves).