Is there any review paper on the theory of Quantum Bayesianism (QBism) developed by Fuchs, Caves and Schack? I know there are a number of papers by these authors but I was wondering if there is a particular one which would be a good starting point and a good summary of their theory. I have already gone through the wiki article. Thank you.


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As a collaborator of Fuchs, I will refrain from making my very first recommendation anything that we have coauthored. Instead, I'll note that the Stanford Encyclopedia of Philosophy has a pretty good article on QBism and related interpretations:


This was written by Richard Healey, who is not a QBist but has an interpretational attitude that is in many ways QBism-adjacent. Being written for an SEoP audience, it is heavier on the philosophical matters and gives less time to the technical research that those matters have motivated.

If you want a whole book that you can carry around, Hans von Baeyer's QBism: The Future of Quantum Physics (Harvard University Press, 2016) is an accurate portrayal, pitched to the interested-layperson audience.

(And incidentally, on the topic of books, Persi Diaconis and Brian Skyrms recently released Ten Great Ideas about Chance, which lays out a school of thought about probability that is pretty much aligned with the one QBism adopts. Diaconis and Skyrms confine the quantum stuff to a single chapter, but they do recommend a David Mermin essay on QBism as good reading.)

Finally, if you want some writing straight from the source, I'll suggest the most recent essay by Fuchs, "Notwithstanding Bohr, the Reasons for QBism":


This is a longish piece ultimately published in a philosophy journal, but it splits the historical/philosophical and technical discussion fairly evenly.

  • $\begingroup$ I've read the SEP article and the Hero's Handbook paper and I have to say that especially the second one is extremely well written and very informative. Thank you both once again (@JohnDeBrota and @BlakeStacey). But I am wondering if there is a paper answering in a direct way to the ''interference objection'', namely that something wavelike needs to exist which causes the interference fringes, and the wavefunction seems to be a good candidate. $\endgroup$ – Floyd May 4 '18 at 13:29
  • $\begingroup$ No direct reference is made to this problem in these two texts, and after a quick check I think Prof. Fuchs does not address this issue in the Bohr paper either. $\endgroup$ – Floyd May 4 '18 at 13:39
  • $\begingroup$ Fuchs and Schack write about interference experiments in "Quantum-Bayesian coherence", <i>Rev. Mod. Phys.</i> 85, 1693-1715 (2013), at greater length than this text box will allow. $\endgroup$ – Blake Stacey May 13 '18 at 15:35
  • $\begingroup$ Rob Spekkens likes to point out that the mere fact of interference itself is not all that quantum, i.e., it arises in models that are fundamentally classical in nature. You just have to be careful and consistent when devising your model. See quant-ph/0401052, in particular section III.G, and also the lecture recorded at PIRSA:16060102. What these models show is that nothing wavelike has to physically, materially exist for interference phenomena to occur. $\endgroup$ – Blake Stacey May 13 '18 at 15:40
  • $\begingroup$ In QBism, what "interference experiments" express is what has to give when an agent insists on writing their subjective probabilities for the outcomes of one hypothetical measurement in terms of their subjective probabilities for the outcomes of one or more other hypothetical experiments. (Say, when they tries to relate a scenario with both holes open to the scenarios with only one hole open.) It's really the same territory as section 2.1 of the "Notwithstanding Bohr" paper; they just don't cut as deeply into the issue as other experiments can, thanks to the point mentioned above. $\endgroup$ – Blake Stacey May 13 '18 at 15:52

Blake Stacey's answer is excellent, but I'd like to point out one more reference he and Fuchs coauthored: QBism: Quantum Theory as a Hero's Handbook. In my opinion this reference is the best single resource to answer your question. The authors explain the principles of QBism in depth and situate them alongside historical motivators, such as teleportation, no cloning, and Bell's theorem. They also address some technical developments stemming from QBism and introduce the more recent QBist-style quantum reconstruction effort mentioned on the wiki page. I should mention that there is not a shortage of philosophical discourse in this paper. I encourage you to soak it up if you want to truly grok QBism.

If you were to read only one more reference, my vote would be for the Hero's Handbook, but the two links and the book Blake mentioned are certainly worthy of perusal as well.

In case it matters, I'm also a collaborator of Fuchs.

  • $\begingroup$ Thank you both (John DeBrota and @Blake Stacey), all recommendations seem very useful. I 'm a pg student in philosophy of science so I'm anyway more interested in the philosophical aspect of QBism. $\endgroup$ – Floyd Apr 26 '18 at 9:59

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