I’m away for the next couple of days. Since comment spamming seems to be getting much worse, I’m turning off comments in the interim. I’ll probably install some kind of comment previewing when I get back.

Categorized as General

Simulating complex quantum systems

On a more scientific note, while I enjoyed many of the talks at the workshop, one stood out for me by far: Ignacio Cirac’s.

Briefly, Cirac talked about a bundle of new methods he and others have been developing in order to simulate quantum systems on conventional classical computers.

Doing such simulations is extremely hard in general, and there are very few quantum systems we can simulate effectively.

This failure is important. The ability to simulate classical systems numerically started in the 1930s and 1940s with the advent of computers, and it has completely revolutionized our understanding of those systems. Because of the difficulty in simulating quantum systems, we’re still effectively stuck back in about the mid-40s with those systems, except in a few special cases.

Cirac talked about the new methods he and many others are developing, based on quantum information theory, for simulating such systems. The details are complex, but the idea is pretty simple: that to do such simulations effectively, the programs must take into account both the ordinary (essentially classical) degrees of freedom, as well as the entangled degrees of freedom.

This is a simple idea, but by pushing on it, people are starting to get some spectacular results. Cirac described a slew of systems that can now be understood using these techniques, and that were previously inaccessible numerically.

It’s early days yet, but if this success continues, it’ll certainly greatly enhance our understanding of complex quantum systems, and mark what may be the first major contribution of quantum information to another field of physics.

Categorized as General

On towers and other things

Back from Pisa.

Obligatory comments on the Tower: it leans, surprisingly much so. No, I didn’t drop anything from the top, although it is tempting. The best thing about the Tower isn’t actually going up to the top, although the view is good, and the inside of the Tower is interesting, if you haven’t seen that kind of thing before (which I hadn’t).

No, the best thing is the view of the Tower from outside, which is much more striking and unique. Best of all, it’s free, not 15 Euros, which is what a trip to the top costs.

Of course, as a third option, you can do what the couple ahead of me in line did. Namely, they paid their 30 Euros, and then decided on the second step up that the inside of the Tower made them claustrophobic, so they quit.

Another interesting event was in the Pisa airport cafe, where I sat down beside what turned out to be some kind of major Italian star, probably a soccer player. At least, he was about 22 or 23, didn’t have movie star good looks (then again, neither do a lot of male movie stars), and he was recognized by essentially every person who looked anywhere near him. I figure soccer is a good bet.

Pretty quickly a crowd started to gather, of people wanting autographs, photos, or just a chance to chat. He took it in extraordinarily good grace. Admittedly, there’s a lot of 23 year old men who wouldn’t find it overly taxing when young women come up and put their arms around them, asking for a photo. (In a few instances, the looks he got were absolutely smoldering.)

With that said, he dealt with all ages and all types with a lot of patience and good will, particularly the few who were tiresome. Outstanding in this category were the snot-nosed brat who complained and kept butting in, and the elderly grandmother who kept him occupied for a good 15-20 minutes, apparently SMSing messages to every single person she’d ever met. So far as I can tell, he was pretty much infinitely patient, and he certainly earned my admiration as a result, although I have no idea who he was.

Categorized as General


I’m away in Pisa next week, for a conference. So I’ll be continuing my recent theme of silence. I’ve a bunch of posts I’d like to make, but they’re taking second place to some other priorities at the moment.

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Assorted Links

A few years back John Horgan published a provocative book “The End of Science”. Here’s Phil Anderson’s take on it. (Anderson, for those who don’t know, was probably the leading condensed matter physicist of the twentieth century.)

David Harris points me to Symmetry Magazine, now in its second issue.

More thoughtful commentary on the US elections from physicist Carl Caves.

Categorized as General