Tuesday, 14 June 2011

Solving Mazes on Mathematica

Just a quick post as I found this very interesting article in the Wolfram blog:

by Jon McLoone

The photo above is from the article. It's an aerial view of the maze at Blenheim Palace, a very beautiful palace here in the UK. The author describes how he used Mathematica (the program) to find a solution to that maze. The most interesting thing is that it used the above photo an nothing else! The whole procedure, with pictures of the intermediate steps, is explained in the article. The final solution, which is what happens with the photo after processing, is this:

This final image is a superposition of the solution, obtained from the image itself, and the original one. Unfortunately, Mathematica is not only not free, but also very expensive. On the other hand, probably all universities have the license for it. Another good result is that I discovered that the Wolfram blog is actually quite interesting to follow... I guess I was a bit prejudiced before.

Friday, 10 June 2011

Negative Entropy and Quantum Observers

I've just read this interesting paper from arXiv:
The thermodynamic meaning of negative entropy, Rio et al.
Landauer's erasure principle exposes an intrinsic relation between thermodynamics and information theory: the erasure of information stored in a system, S, requires an amount of work proportional to the entropy of that system. This entropy, H(S|O), depends on the information that a given observer, O, has about S, and the work necessary to erase a system may therefore vary for different observers. Here, we consider a general setting where the information held by the observer may be quantum-mechanical, and show that an amount of work proportional to H(S|O) is still sufficient to erase S. Since the entropy H(S|O) can now become negative, erasing a system can result in a net gain of work (and a corresponding cooling of the environment).
The main point is an idea of the authors about Landauer's erasure principle applied to quantum memories. There is a less technical description, but with a no less catching title, in this article: Erasing data could keep quantum computers cool.

The authors suggest that a quantum observer can use Landauer's principle to extract heat from the environment instead of throwing heat on it, effectively cooling instead of heating. I'm not a specialist in quantum computing and I didn't go through the arguments of the paper in much detail, but I will be a little skeptical about that and I will explain why. As far as I understood, in order to derive the result the paper assume the existence of a "quantum observer" and give the example of a quantum memory. That is not very clear to me. In fact, if the final idea is to use it in real computers, the ultimate observer will have to do a sharp measurement in the end and will obtain a definite number. The very idea of a quantum observer seems strange to me in the sense that all observers are obviously quantum, but somehow the measurement of a property will cause the decoherence of the entanglement between the observer and the system.

If someone wants to share the thoughts about that paper, please feel free. It seems to be an interesting work, but I would like to understand it better.

Friday, 3 June 2011

Stupid World

I've been blogging about the world entering a New Dark Age for some time, but news like this one make me think that instead of Dark, I should call it Dumb Age:

Apart from the fact that most politicians are not even capable of predicting the consequences of their own actions, any medium educated person knows that it is not possible to predict this kind of natural event yet. I would add more. With high probability, this is due to the fact that governments (and I'm not saying most, I'm saying all of them) don't give a damn to research in this area until something really bad happens.

What really happened is that politicians and government officials wanted to blame someone for the 2009 earthquake 08 casualties in Italy, when of course they were the guilty ones. As always, they found a scapegoat in the weakest link of the chain. The scientists are facing trial for something which is just barely lighter than genocide. The judge of this case is Giuseppe Romano Gargarella and, in his own words, the seven defendants had supplied "imprecise, incomplete and contradictory information," and in doing so, they "thwarted the activities designed to protect the public."

Note that a judge is someone who is supposed to have attended a university course in law, but even if the subject of his graduation was only law, I thought that any graduate student should have an understanding about how science works. The judge clearly doesn't, which is a severe failure in whatever system of education he graduated.

This kind of judgement is so stupid and so clearly abusive and misleading that should be considered even criminal in the present world. For those interested in a much more detailed analysis and much harsher comments than mine, I leave you with Lubos:

One last word. If you're a scientist, please react! These kind of things only keep happening because most of the times we are afraid of reacting properly. Spread the news, complain about that, do something to draw attention to it. At least people will know how dangerous are those who are supposed to be our leaders.

PS: The photo is from a protest that has nothing to do with the news, but I thought that the message carried by the protesters was appropriate for the moment...