Quantum Bayesian Networks

April 9, 2012

Quantum Bayesian Networks, The Ultimate Mixology Guide

Filed under: Uncategorized — rrtucci @ 7:30 pm

Check out my new paper

An Introduction to Quantum Bayesian Networks for Mixed States
by Robert R. Tucci (arxiv abstract)

The paper is a fairly elementary pedagogical introduction. It’s sort of a prelude to a more researchy paper that I am trying to write next.

I’m very pleased that I was able to draw all the pictures of the paper in LaTex “native” fashion, using only LaTex macros (xypic and cancel). The LaTex Gods have been generous to me once again.

This was the original cover of the paper, but my editor nixed it:

Picture Credits:

The drawing of a man making snow angels on the sand of a sandbox is of course The Vitruvian Man by Leonardo da Vinci. So why did Leonardo write backwards? Historians don’t know for certain but many believe it was because Leonardo was left-handed and he wanted to write quickly with a quill pen without smudging the ink with his hand.

The drawing of a letter U with an eyeball resting on the fat (classical) leg of the U could have been a sketch done by an abstract modernist painter like Dali or Picasso, or it could have been a depiction of a creature from another planet, the u-tube cyclops?, but it’s really a drawing made by John Archibald Wheeler (professor at Princeton Univ. for almost 40 years, PhD advisor to Richard Feynman, Hugh Everett and many, many others). The drawing symbolizes the feedback between the observer and the observed in quantum mechanics.



  1. Very much looking forward to read through this. BTW I am wondering if you heard of Kinsley Jones thesis that applies theory of Bayesian Inference to QM? This is one of those papers that is on my back-burner to read (the PDF copy I have is so crappy that I finally decided to order a hardcover).

    Comment by Henning Dekant — April 10, 2012 @ 3:10 am

  2. Note that even though Bayesian networks are closely related to Bayesian inference, they are not the same thing. For one thing, you can do Bayesian inference without using Bayesian networks.

    I’m not familiar with this bloke’s work. I think you meant “Kingsley”. I googled “Kinsley Jones quantum” and got a “did you mean Kingsley Jones quantum” I believe you are referring to the author of this young blog. He says he is currently a hedge fund manager and that he got his PhD about 15 years ago. Good! I wouldn’t mind making friends with some rich people. Maybe being rich is contagious.

    Comment by rrtucci — April 10, 2012 @ 1:50 pm

  3. He’s a very approachable fellow. Crossed his paths in the LinkedIn QIS group where he handed out PDF copies of his thesis. His research funding dried up which is why he had to pursue a business career. His heart is apparently still very much with physics and he wrote that he’ll be happy to compare notes with you.

    Didn’t even know he had a blog, but the one you found is definitely his.

    Comment by Henning Dekant — April 10, 2012 @ 9:05 pm

  4. Hi Henning (and Kingsley) I looked at the thesis briefly. Interesting. Maybe someday I’ll look at it more carefully. Right now I’m more concerned with quantum Bayesian networks rather than Bayesian inference.

    Comment by rrtucci — April 12, 2012 @ 3:47 am

  5. […] instance, there is Robert Tucci's remarkable work to extend Bayesian Network diagrams into the quantum computing realm.  There are also considerable efforts underway to develop a universal visual Tensor Network […]

    Pingback by A Picture is Worth More Than a Thousand Lines of Code | Wavewatching — May 18, 2012 @ 5:05 pm

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