Quantum Bayesian Networks

November 27, 2012

Understanding, Proving and Explaining

Filed under: Uncategorized — rrtucci @ 5:00 pm

I’m an old-fashioned physicist. I know very little about complexity theory. Maybe some day I’ll learn more about it. Nevertheless, I recognize that complexity theory is quite important to this quantum computing joint quest of ours. (although not as important as physics and engineering 🙂 ) But note, dear physicist reader, that complexity theorists and other mathematicians “are different from you and me”.

Understanding without proving (what physicists do)
Proving Without Explaining (what mathematicians do)
Explaining Without Understanding (what I do)

Complexity Theorist Scott Aaronson recently gave a talk at UPenn Law School. I had a lot of fun reading the Powerpoint slides of the talk. Check them out. They are not very technical, as one would expect, considering that they are intended for a general audience.

In the comments section of Scott’s blog, I posed the following question:

Can one define quantum proofs very generally so that probabilistic, interactive and zero knowledge proofs are special cases of quantum proofs? Classical probability is a limit of quantum mechanics, interactive depends on what observables one is allowed to measure, zero knowledge sounds like the least number of observables are allowed to be measured.

My question turned out to be a dumb one, but Scott nevertheless patiently answered it. Thanks Scott. You can read Scott’s answer here.

I still think it would be cool if you could build a machine called a Quantum Prover, such that all other provers were special cases of it. The Quantum Prover would be the baddest, fastest gun in the West. It could simulate all other provers and either match or outperform them in speed and efficiency. Plus it could do extra stuff that the other provers couldn’t do.

The American science fiction writer Greg Bear features in many of his novels what he calls “quantum logic thinkers (QLs)”, or just “quantum thinkers”.

Today, bayesian networks are an important tool in Google’s tool chest. If quantum provers ever come to pass, no doubt Google will have to upgrade its tools from classical bayesian networks to quantum bayesian networks…

The Quantum Fog 9000

Quantum Johnnies at Google

November 18, 2012

Richard Chirgwin at the Register

Filed under: Uncategorized — rrtucci @ 12:17 am

Check out

What are quantum computers good for?
Forget cracking crypto, think modelling reality itself to help build a better one
Posted in The Regiter/Science, 17th November 2012 20:00 GMT
By Richard Chirgwin

Ritchie Chirgwin just published this article in The Register, a British tabloid. The article is a long, soporific piece. Not very original. Writing skill level: about that of a C minus high school student. I tried to submit a comment to his article, twice, to no avail. I wanted to point out some serious errors, but Ritchie will have none of it. How dare I find fault with Narcissus! So I submit my comment here instead:

Sorry, Mr. Chirgwin, but your article is full of false statements. Here are some. You say:

(1)“In certain settings a quantum computer is exponentially more efficient at performing Fourier Transforms than a classical computer.”

That is totally false. A QC can calculate faster than classical computers only “quantum” Fourier transforms, not “classical” Fourier transforms. They are quite different. For a classical Fourier transform, you can “print” all N components of the answer at the end of a each “run”. For a quantum Fourier transform, you can “print” ONLY ONE of the N components of the answer at the end of each “run”. The other N-1 components are destroyed when you print that single one.

(2)“Today, the problem is approached by sampling, using the Metropolis algorithm on a classical computer. The European/Canadian group propose an alteration to that algorithm that uses a quantum computer to obtain the samples.”

Again, very misleading.
The statement refers to the following paper:
http://arxiv.org/abs/0911.3635
Quantum Metropolis Sampling
K. Temme, T.J. Osborne, K.G. Vollbrecht, D. Poulin, F. Verstraete

The problem with this paper by Temme et al is that it not very honest. It doesn’t tell you that their QC algorithm is no faster than classical. There are known QC algorithms which PREDATE the Temme et al algorithm and which can sample faster than classical. They use the Szegedy operators. (See, for example, the work by Rolando Somma, Pawel Wocjan, and my own program called Quibbs). The Temme et al paper doesn’t compare their algorithm with those earlier, faster algorithms because they would look quite bad in the comparison. Like I said, they aren’t very honest.

(3)“Another example is here: a quantum algorithm for solving linear equations (where you have a matrix and a known vector, and wish to compute an unknown vector). For some classes of linear equations, Harrow, Hassidim and Lloyd have demonstrated that a classical computer’s runtime will be exponentially greater than that of a quantum computer.”

That is totally false. Again, with the classical algorithm for solving linear equations, you can print all N components of the answer, but with the quantum one you can “print” ONLY ONE component per run. Equating these two algorithms is quite disingenuous. Check out this post by Eric Dexler, one of the fathers of nanotech:

http://metamodern.com/2009/11/10/quantum-computing-sorry-no-speedup-in-solving-linear-systems/

November 9, 2012

Evolution of Man

Filed under: Uncategorized — rrtucci @ 8:09 pm


(This picture was not conceived by me. I don’t know who made it.)

Next stage: (wearing a space suit) Homo Quantis Bayesianis Reticula

Did the sun just explode?

Filed under: Uncategorized — rrtucci @ 7:57 pm

From Xkcd comics

November 6, 2012

The Prutchi Girls Love Pink Noise

Filed under: Uncategorized — rrtucci @ 6:36 am

Check out

Hacking the Quantum: A New Book Explains How Anyone Can Become an Amateur Quantum Physicist
By George Musser, October 22, 2012

David Prutchi is a PhD experimental physicist and engineer. He has 3 daughters: Shanni (the oldest, currently a senior in high school), Abigail and Hannah. They live in Philadelphia. Their dog’s name is Schrodi, after Erwin Schroedinger (a notorious Casanova also known for some physics). David’s main job is designing medical devices. But, as many of us do, to make ends meet you know, he has a secondary part-time job, as a quantum mechanic in his garage. David and Shanni have recently written a “do-it-yourself” quantum physics book entitled

Exploring Quantum Physics Through Hands-On Projects
amazon link for book

The Prutchi website http://www.diyphysics.com covers the book and much more. Note that diy stands for “do it yourself”

The depth and scope of the home experiments detailed in the book is nothing short of amazing. Sit down before you read this: Here is a listing of the contents of their book.

Congratulations to the Prutchi’s from an awestruck fan. You guys are true homebrew-hacker Jedi masters. I hope someone in your family starts a quantum computer company some day soon.

(I love your garage lab, including your dog technician. I also like very much your surname…Nice, strong, distinguished sounding. Reminds me of mine, Tucci)

November 2, 2012

Interview With The Vampire

Filed under: Uncategorized — rrtucci @ 3:17 am

(a Halloween story by Anne Risotto)

It would be no exaggeration to say that I had been preparing my entire life for this job interview. And now, that long awaited day had arrived. At midnight, I had been summoned telepathically to the town’s ancient castle. I was now being interviewed by the most famous man in the business, Count Dracula himself. 

Flashback: It all started innocently enough. I remember clearly when at age 6, I first saw a “Bill Nye The Science Guy” TV program. Right there and then, I had decided that I wanted to be one of them. My high school math teacher had been truly inspirational, and had encouraged me to follow this ambition of mine. Of course, back then, I was young and innocent—I thought my vampire idols were noble people altruistically and valiantly trying to do good in the world. How proud my family was when I was admitted to MIT! There I obtained a BS and a PhD in vampirism. Shortly thereafter, I was hired as a postdoc at a prestigious vampire firm. And now I was being addressed in an erie, mesmerizing voice, speaking in perfect English, but with a subtle Rumanian accent, by Count Dracula himself.

“Good, my son. I see that you have the right transylvanian pedigree for this job. Your thesis advisor, the man who trained you in the dark arts of vampirism, is feared, hated and reviled by all those who know him. It is said that he is amoral and has no conscience. Furthermore, he has a very high opinion of himself and of his caste, and he thinks he will live forever. All good traits for a successful vampire to have.

Hmm, But are your squeamish about sucking blood, my son? I suspect not. 

You are hired. Starting next term, you will be an assistant professor in quantum computing at this illustrious vampire university. Our job as university administrators is to suck dry of blood the parents of your students. As for you, your job is to suck dry all Government Agencies that fund research.”

Vlad the Impaler

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