Tag: physics

Quantum Stochastic Walks

It took some time with the printing proofs, but finally, the paper has been published.

Quantum stochastic walks: A generalization of classical random walks and quantum walks

We introduce the quantum stochastic walk (QSW), which determines the evolution of a generalized quantum-mechanical walk on a graph that obeys a quantum stochastic equation of motion. Using an axiomatic approach, we specify the rules for all possible quantum, classical, and quantum-stochastic transitions from a vertex as defined by its connectivity. We show how the family of possible QSWs encompasses both the classical random walk (CRW) and the quantum walk (QW) as special cases but also includes more general probability distributions. As an example, we study the QSW on a line and the glued tree of depth three to observe the behavior of the QW-to-CRW transition.

Phys. Rev. A 81, 022323 (2010)

Previously: video abstract

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Man, you come right out of a comic book. -Enter the Dragon

The Nucular Family

Friends have asked me many questions about Obama’s nuclear plan. Although, I am not a nuclear physicists, I did get trained, have been around and/or managed radioactive material while at a Oak Ridge National Lab and University of Texas.

What surprised me was that although I tried to explain each of the different risks, trying to distinguish between radiation exposure and material toxicity, my friends demanded, begged, for apocalyptic scenarios of devastation. This is very much like discussing air travel safety by discussing TWA Flight 800 only, ignoring statistics, ignoring how cars are much more dangerous, and only focusing on what is relevant for a bad blockbuster movie.

Let me be clear, I am not defending nuclear plants disasters, I am not dismissing all the risks of nuclear powered plants. I am surprised how it is impossible to discuss the risks. Any risks involves understanding the different kinds of dangers multiplied by the possibilities of those happening. Without this, benefit, cost and risks analysis are impossible. Without this analysis, public policy cannot be discussed. Why are we so afraid of the dangers of nuclear power, but we are never worried about all the dangers of coal-powered plants? Why, cognitively, these dangers feel so different in our heads? Why in the public eye, nuclear power isn’t about environmental science and economics, but about the apocalypse? This raises many questions about the nature of fear in society, questions I have no answers to.

For example, Nuclear Magnetic Resonance is a standard medical (and general science) technique. It doesn’t have to do with atomic energy, just with the fact that each of the atoms we are made up has a nucleus that consists of protons and neutrons. However, the ‘nuclear’ name had such negative connotations that the name was changed to “Magnetic Resonance Imaging”. Why is this?

My dad has gone through several medical techniques in the past years, including MRI (Nuclear Magnetic Resonance), PET Scan (Positron Emission Tomography) and Radioactive Iodine treatment. He is concerned about the effects of all those nuclear things. I tried explaining how the techniques are very different, containing no radiation, or different kinds of radiation, emphasizing that there is no heavy-metal toxicity in each of these, discussing what does the half-life of iodine really mean to his body by considering that iodine is water soluble, explaining that microwave ovens aren’t dangerous or nuclear, nor are TVs, nor cellphone radiation is of nuclear origins. I did spend significant time talking to my family about this, and maybe it was my fault, maybe I talked over the heads. I was unable to dispel irrational fears in my family, fears that weakened their spirits while my dad was going through an already difficult medical process.

Maybe I was unable to reach them because we meant different things. Maybe there is a very significant difference in the meaning of nuclear to them and to me, a difference in meaning I wasn’t able to overcome with all my explanations.

Why is it so hard for the general public to discuss these issues? Why is discussing nuclear power a taboo? I propose to blame cognition, an image in the mind. After the end of World War II, after the cold war, after The Hulk, the term “nuclear” started carrying a lot of overhead, a lot of imagery and meaning beyond its semantic nucleus of the word [pun].

Bruce Banner, Physicists, demonstrating the effects of Nucular Power
Bruce Banner, Physicist, demonstrating the effects of Nucular Power

My proposal is the following. There are two different kinds of ‘nuclear’ in the public mind:

  1. nuclear as in nuclear family, nucleus as in “the core”
  2. nuclear, as in atomic bombs, as in neon glowing toxic rods, as in mutated turtles that learn ninjitsu, as in Cold War, as in nucular.

However, there is only one nuclear in the physicists’ mind, which refers to the core of the atom, which refers to protons and neutrons, which refers to the forces that keep the nucleus stable and make the existence of matter possible, a meaning which is closer to nuclear family than to nucular. It has nothing to do with mutagen, or Homer Simpson and is as far from a nuclear wasteland as Bernoulli’s principle is from crash landing. The same applies to the word “atomic”, that to the general public feels more like “ka-BOOM” than “a tiny piece of anything”.

Is this why there are many public figures that mispronounce nuclear in favor of nucular? Is it that their minds want to distinguish between these two definitions? A linguist at Berkeley suggests this as he explains ‘nucular’ as a folk etymology, not as mispronunciation.

Phonetically, in fact, nuclear is pretty much the same as likelier, and nobody ever gets that one wrong. (“The first outcome was likular than the second”? )

Maybe there are two different meanings of nuclear in the public mind, maybe the nuclear taboo and the word nucular are signs of this. Maybe this is why discussing the dangers and possibilities of nuclear power is so difficult.

What is the solution? I see only two options:

  1. invent an euphemism for the word “nuclear” in nuclear power. Call it “freedom power”, “awesome fuel” or “funky style”,
  2. start calling everything nucular, trying to reunite both misleading diverging meanings. Like, “the nuculus of the cell contains the DNA” and “nucular families are the basis of society”

I don’t see any other option that could allow having a public discussion of the pros/cons of nuclear power as public policy, instead of nuclear disaster as a Nostradamus predictions. An apocalyptic image, even if unfounded, has a lot more power than statistics, power that brings out pure fear, preventing all rational discussion. Remember when the news focused on the dangers of black hole creation when the LHC started, instead of actually explaining what the particle accelerator actually does?

Nucular is fear.

If there are any social psychologists around there, can you contact me with references about the origin, nature and effects of fear in society?

—

Vamos a seguir bailando!
Vamos a seguir contento!
y sigamos vacilando!
Vamos a seguir en esto,
porque un dia de estos.
Que tu veras que va llegar un demonio atomico.
y atracata acangana! y nos va limpiar.
Despues de muerto no se puede gozar!
-El Gran Combo

2010 is a good year (so far)

2010 has been awesome so far. I’m having a hard time keeping up with blogging all the good news.

Talks

I was in invited The Winter Meeting on Statistical Mechanics in Taxco, Mexico. What a fantastic conference! I learned a lot about many different areas in Statistical Physics, got to meet many awesome researchers, and the keynote talks were in a natural amphitheater inside the Cacahuamilpa caves. Stunning! This was one of the best conferences I’ve been to.

I was also invited to give a talk at Reed College last week. This was my first time ever in Portland, Oregon, and I fell in love with the city. It felt like a mixture of Austin, Northern California and Seattle that I really liked. The academic culture at Reed is something that should be emulated everywhere: students honestly don’t care about grades, just about learning. One thing is to hear it, and another is to witness how true it is! The physics department at Reed has the most motivated and energetic physicists I’ve ever met. Wow.

Papers:

Finally, the paper that I had mentioned before appeared in PRL:

Time-Dependent Density Functional Theory for Open Quantum Systems with Unitary Propagation

Also, the PRA on assignment maps is out in the published wild.

Linear assignment maps for correlated system-environment states

How not to lie about Quantum Mechanics?

Writing for the general public about science news is hard. ArsTech has an article where they accuse many news organizations of deliberately lying in their science coverage, and discuss how they can get away with it do to double standards.

As a scientist with interest in informing the public of my research, are there any guidelines to follow when talking to the press? I want them to see them as allies, but most of the science news are so bad I can’t help but hating them.

I’ve thought much about how to describe my research to family and friends, and haven’t found any good and concise way to do it. More specifically, can any one suggest any good, simple, cocktail-party style one-liners to explain what is quantum mechanics and quantum computing, but that doesn’t make me feel like I’m lying? If I read again the phrase “what Einstein called spooky action at a distance” I might vomit.

Any ideas?

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When Men fly from danger, it is natural for them to run farther than they need.
-The Mischiefs that ought justly to be apprehended from a Whig-goverment

SQuInT, APS, Publications

I’m back.

After a long, tough, wintery and busy month, I’m back.

Progress report follows.

Alright, first, I went to SQuInT. The Southwestern Quantum Information and Technology conference isn’t true to its name. It was held in the Northwest, Seattle, where beautiful weather seemed to tunnel through the mountains’ potential just for us. The conference itself was very productive and I had the opportunity to see family, friends and collaborators.

In other news, we submitted a paper on Open Quantum Systems and Time Dependent Current Density Functional Theory titled Time-dependent current-density functional theory for generalized open quantum systems to the journal Physical Chemistry, Chemical Physics (PCCP). It has been accepted for publication and might appear in a special issue on Time Dependent Density Functional Theory.

We also submitted a related paper to another journal, paper titled Time-Dependent Density Functional Theory for Open Quantum Systems using Closed Systems. You can read it in the arXiv.

Finally, I went to the APS March Meeting, where 7,000 physicists took over the city of Pittsburgh, where I was able to find bars decorated with Roberto Clemente posters, where a restaurant served Carrucho (Conch). Sometimes I feel the APS March meeting is too big, too overwhelming, talks are too short, and there is too much going on simultaneously. But then I’m surprised by meeting people I hadn’t seen in almost 10 years now, and by how APS March meeting always lead to new collaborations.

Exciting times these are.

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“I have wept three times in my life. Once when my first opera failed. Once again, the first time I heard Paganini play the violin. And once when a truffled turkey fell overboard at a boating picnic.”
-Gioachino Rossini