Quantum Bayesian Networks

January 13, 2019

Qubiter compared with other wines

Filed under: Uncategorized — rrtucci @ 4:49 am

The following cartoon by the famous author James Thurber makes me think of Qubiter as a young upstart wine and of myself as a wine lover.

Here is a table pointing out several cool features that Qubiter already has but that the 3 other most popular quantum computer languages don’t all have. (Having a feature is indicated by a gold star). I am sure that the big 3 will eventually catch up with Qubiter, but it may take a long time because big generic software/wine manufacturers can sometimes move as slowly as molasses.


I have previously compared Qubiter with the 3 other major qc languages using analogies to sea vessels



January 11, 2019

Qubiter now has Placeholders for gate angles

Filed under: Uncategorized — rrtucci @ 5:38 am


The word “Placeholder” is used in Qubiter (we are in good company, Tensorflow uses this word in the same way) to mean a variable for which we delay/postpone assigning a numerical value (evaluating it) until a later time. In the case of Qubiter, it is useful to define gates with placeholders standing for angles. One can postpone evaluating those placeholders until one is ready to call the circuit simulator, and then pass the values of the placeholders as an argument to the simulator’s constructor. Placeholders of this type can be useful, for example, with quantum neural nets (QNNs): in some QNN algorithms, the circuit gate structure is fixed but the angles of the gates are varied many times, gradually, trying to lower a cost function each time.

This brief blog post is to announce that Qubiter now has such placeholders. Hurray! Placeholders is a nice feature that Google’s qc simulator Cirq and Rigetti’s qc simulator PyQuil, already have (they call them parametric or symbolic gates), so it has been irking me for some time that Qubiter didn’t have them too. Got to keep up with the Joneses and the Kardashians, you know.

Qubiter implements placeholders via a class called PlaceholderManager. You can already read an example of placeholder usage in the main() method at the end of that class. I also intend to write a Jupyter notebook, probably this weekend, illustrating their use.

January 10, 2019

IBM Relases 20 Qubit Commercial Quantum Computer, Code Name “batbeer tank”

Filed under: Uncategorized — rrtucci @ 6:53 pm

On Jan 8, IBM unveiled the “World’s First Integrated Quantum Computing System for Commercial Use”. Just imagine, deep down in a shadowy batcave in Yorktown Heights, New York (conveniently located next to Gotham City), in a dank, dark corner of an already dark cave, a brewing tank for producing inky black batbeer, made with mysterious black waters found in the cave. Here is what it looks like (bat beer logo by Tony Matýšek)

There is a vast amount of prior research about the scientific subject of batbeer . Here is a small fraction of such work. This list was provided to us by U.S. Supreme Court Justice Brett Kavanaugh, compiled by him during one of the rare moments when he is sober and not barfing, or lifting weights with his buddies “P.J., and Squi, and Handsy Hank, and Gang-Bang Greg” (SNL/Matt Damon verified fact) , or dutifully filling his 2019 calendar/lab notebook. You can Google the keyword “batbeer” yourself and obtain a more complete reference list.


January 5, 2019

Daphne Koller: “Use the Bayesian-Network-Force, Luke. Let Go!”

Filed under: Uncategorized — rrtucci @ 7:47 pm

Daphne Koller, Stanford Prof., writer with Nir Friedman of a monumental and ground breaking book on Bayesian Networks, inventor of the concept of Markov blankets (my favorite security blanket) and much else related to B nets, cofounder with Andrew Ng of the Coursera MOOC company, where she taught a course based on her B net book, is at it again. On May 2018, she founded the startup Insitro (home page, crunchbase page) which promises to leverage the power of Bayesian Networks for drug discovery. At artiste-qb.net, we are big advocates of applying quantum bayesian nets (invented in 1997, also the name of this 10 year old blog) to quantum computing.

January 4, 2019

A quantum computing paradox, Generalized Toffoli Gates

Filed under: Uncategorized — rrtucci @ 12:32 am

Call me Simplicio.

Let a Generalized Toffoli (GT) gate be a quantum gate, acting coherently on N+1 qubits, that rotates a target qubit subject to the state of the other N qubits acting as controls. If you calculate, with a classical computer, the effect of a GT gate on an input state vector, the larger N is, the fewer multiplications you will have to perform. On the other hand, if you expand a GT gate into a sequence of single qubit rotations and CNOTs, the minimal number of CNOTs in such an expansion will grow exponentially in N. Huh?

This paradox seems to imply that it behooves quantum computerists to find a way of implementing GT gates in their hardware in a single step, as I advocated in this previous blog post of mine.

January 3, 2019

Primo job opportunity, Quantum Computing Job at Tencent America

Filed under: Uncategorized — rrtucci @ 8:12 pm

At artiste-qb.net, we admire Tencent very much. Our Bayesforge docker image is on the Tencent cloud. See


So we want to alert our friends to the following job opening:

Senior Researcher – Quantum Computing
Company Name: Tencent America
Location: Palo Alto, CA, US

Posted 3 weeks ago


Nostradamucci Prediction for 2019: Qubit Ring Molecules and Generalized Toffoli Gates will be crucial for quantum AI

Filed under: Uncategorized — rrtucci @ 5:09 am

Nerdy, speculative blog post ahead. Better skip this one and go on to the next one. Or, if you want really speculative, stoner lit., read a Quanta Magazine article instead.

Read this at your own peril!

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