Quantum Bayesian Networks

June 1, 2014

QBism != Quantum Bayesian Networks

Filed under: Uncategorized — rrtucci @ 12:23 pm

I would like to point out here that the interpretation of Quantum Mechanics (QM) known as QBism, espoused by Chris Fuchs, N. David Mermin, and others, is not related in any close way to Quantum Bayesian Networks (qbnets). I’ve never discussed either QBism or qbnets, either personally or by email, with Fuchs or Mermin or any of the other proponents of QBism. I’m not a friend or even an acquaintance of any of those guys. As far as I know, Chris Fuchs has never mentioned qbnets in any of his papers (not even in his two voluminous email collections published in arXiv). Hence, he has never shown the slightest interest in qbnets. I, for my part, have never been too interested in QBism either. In fact, I’m not too interested in any interpretation of QM. I’m mostly a shut up and calculate guy.

The theory of qbnets follows logically from the standard, widely accepted, axioms of QM. One might say qbnet theory is agnostic to QM interpretation. I consider that to be one of the assets of this theory: even many-world crackpots/mystics can profit from qbnets. 🙂 QBism, on the other hand, is strictly an interpretation of QM. Many-world advocates see little of value in QBism, because it’s a different religion than theirs.

In classical Statistics, one distinguishes the frequentists and Bayesian approaches. The Bayesian approach seems to be more general than the frequentist one because it gives probabilities for everything the frequentist approach does, plus it gives probabilities for events (like the outcome of a future horse race) that the frequentists REFUSE, as a matter of principle, to give any probabilities for. What is the point of QBism? Is it to say that the Copenhagen interpretation (a.k.a shut-up-and-calculate) is a frequentist approach and QBism is a Bayesian approach? If so, then does QBism give probabilities for some events that the Copenhagen interpretation advocates refuse, as a matter of principle, to give probabilities for? What are those events? I’ve never heard of the shut-up-and-calculate people refusing to calculate anything. It seems to me that from the earliest days of QM, the Copenhagen interpretation has included BOTH the frequentist and Bayesian camps. QBism seems to me to be just a rebranding of the Copenhagen interpretation by corporate America.

(I just learned from Wikipedia a funny example of rebranding. The notorious company formerly called “Blackwater” (black ops contractor boasting of being the largest private army of mercenaries in the world) is now called “Academi“. So Blackwater has joined the ranks of Academia. Welcome home!).

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Got this image here



  1. All famous were the black waters of Styx in the ancient times…


    Comment by Elangel Exterminador — June 2, 2014 @ 11:30 pm

  2. QBism is so bizarre I can’t help thinking it’s a parody. It literally claims that people created the laws of quantum mechanics, and that the statistical results of quantum experiments are non-classical only because we believe them to be.

    Comment by collin237 — November 23, 2015 @ 12:54 pm

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