QBism, also called Quantum Bayesianism, is an interpretation of quantum theory which gives a subjective Bayesian account of probabilities in quantum theory. Rooted in the prior work of Carlton Caves, Christopher Fuchs, and Rüdiger Schack during the early 2000s, QBism itself is primarily associated with Fuchs and Schack and has more recently been adopted by David Mermin and promoted by Nobel Laureate Theodor Hänsch. QBism draws from the fields of quantum information and Bayesian probability, claiming to correct, clarify, and extend the viewpoint on quantum mechanics that is commonly presented in textbooks.
- QBism, which combines quantum theory with probability theory, maintains that the wave function has no objective reality. Instead QBism portrays the wave function as a user’s manual, a mathematical tool that an observer uses to make wiser decisions about the surrounding world—the quantum world.
- Hans Christian von Baeyer, "Quantum Weirdness? It's All in Your Mind", Scientific American (June 2013)
- QBism explicitly takes the “subjective” or “judgmental” or “personalist” view of probability, which, though common among contemporary statisticians and economists, is still rare among physicists: probabilities are assigned to an event by an agent and are particular to that agent. The agent’s probability assignments express her own personal degrees of belief about the event.
- Christopher A. Fuchs, N. David Mermin and Rudiger Schack, "An introduction to QBism with an application to the locality of quantum mechanics", American Journal of Physics 82, 749 (2014)