QBism (Quantum Bayesianism)
Christopher FuchsN. David MerminRüdiger Schack
This page delivers no verdict; it presents claims and evidence with their sources. No theory in science is absolute. Method
For everyone
According to QBism the wave function expresses not the world itself but an agent's personal beliefs about their own future experiences. A measurement is an action the agent takes on the world and the new experience received in return; "collapse" is just the updating of belief with new information. The interpretation reads quantum probabilities within Bayesian probability theory and is one example of epistemic approaches that treat the wave function as information.
For specialists
QBism treats quantum states through de Finetti's subjective interpretation of probability. The Born rule is rewritten as a "normative" rule for coherence among an agent's probability assignments. In this interpretation the problem of non-locality is handled differently, by taking measurement outcomes to exist for each agent only as their own experience. In Wigner's-friend-type thought experiments, different state assignments by different observers do not count as a contradiction.
Claims
- A quantum state represents an agent's personal (Bayesian) probability assignments for measurement outcomes; it is not a physical object.[1]
Positions
- Critics
- Grounding the theory in personal beliefs amounts to giving up science's aim of describing a world independent of observers.[2]
Connections
Sources
- Article (2014). An introduction to QBism with an application to the locality of quantum mechanics. American Journal of Physics 82(8), 749–754DOI 10.1119/1.4874855archive
- Article (2025). Physicists disagree wildly on what quantum mechanics says about reality, Nature survey shows. Nature 643, 1175–1179DOI 10.1038/d41586-025-02342-yarchive
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Cite this page
Athena contributors. (2026). QBism (Quantum Bayesianism). Athena: The tree of human knowledge. Retrieved November 1, 2026, from https://latifkedi.github.io/athena/en/d/qbism/
@misc{athena_qbism,
title = {QBism (Quantum Bayesianism)},
author = {{Athena contributors}},
year = {2026},
howpublished = {\url{https://latifkedi.github.io/athena/en/d/qbism/}},
note = {Athena: The tree of human knowledge. Accessed: 2026-11-01}
}Added: September 28, 2026 · Last changed: September 28, 2026 · Page history