Saturday, June 27, 2009

A cool result

There's a new asap paper in Nano Letters that is very slick. There has been a lot of interest in the last few years in plasmonics - the controlled manipulation of plasmons, collective oscillations of the electronic fluid in metals. Plasmons are pretty remarkable excitations. Because they involve displacement of the electron density, they necessarily result in local electric fields near metal surfaces (useful for optical antenna sorts of effects), and they can (under the right circumstances) couple efficiently to electromagnetic radiation. Plasmon response to light can be very pronounced, ranging from resonant scattering or absorption (for example, why certain types of glass are colored) to more complex dispersive effects, including negative (effective) indices of refraction. Plasmons are also responsible for helping light to transmit through sub-wavelength apertures. However, as far as I know, until now none of these effects have depended in any significant way on the angular momentum of light. In this new result, researchers from the Technion in Israel have designed aperture structures that can couple selectively to left- or right-circularly polarized light. The trick is in finding a situation such that the angular momentum of the light (essentially the spin of the photons) couples selectively to plasmon modes in the apertures that have matching orbital angular momentum. I don't fully understand how the two experiments described in the paper work, but it's a neat, clever result.

Monday, June 22, 2009

Four items

Four items, and a physics post later in the week.
  • Is "just-in-time" supply chain management truly the work of the devil, or merely incredibly annoying? We've had a problem with a gate valve on a piece of cleanroom equipment at my institution, and the vendor (a) has no spare valves; (b) has no spare parts for the valves; and (c) says it'll take around 4 weeks to fab a replacement valve. Now, I understand why a business wouldn't want a huge inventory sitting on shelves, and that there are real fixed costs associated with inventories. Still, how hard would it be to have some spare parts, particularly when these things don't go bad when stored? I can tell you that it doesn't make me predisposed to ever buy anything from this supplier again. So, while it may be penny-wise, it sure feels pound-foolish for companies to alienate customers by having no backup supplies at all.
  • Ahh, scientific publishing. Two folks from Cornell used an amusing computer program to generate a grammatically correct but completely nonsensical fake paper (pdf). They then got that paper accepted to an open-access journal, without the knowledge of the editor (!), with the strong implication being that this publisher was willing to publish literally anything as long as the authors are willing to pay the fees. Wonderful. I've suspected for a while (basically when a couple of publishers spammed me about being a contributing editor on journals I'd never heard of, back when I was a brand new assistant prof) that there are some shady practices out there.
  • Also regarding scientific publishing, I was shocked and appalled (ok, not really, but certainly surprised) when I got the proofs of an article that we have coming out in Phys Rev B. Why? Because it was clear from the marked-up "author query" version of the manuscript that the AIP production office had converted our beautiful LaTeX manuscript into Microsoft Word format for editing. What is the world coming to?!
  • Lastly, I was fortunate enough to receive a new iPod Touch as a gift. Anyone out there have suggestions for must-have apps?

Monday, June 15, 2009

The revolution will be twittered.

Not a physics post, but an observation. There is a major event going on in Iran right now - protests involving many thousands of people; rioting; the most political upheaval since the 1979 revolution. I hope that everything works out for the best - any country with a Supreme Leader needs a new governance structure, IMO. Anyway, twitter is being used as a major tool by the Iranian protesters. So much for my general perception that twitter was only for people more self-indulgent than bloggers (ahem.). It's fascinating and alarming to watch events unfold from halfway around the world, while CNN reports on things like Sarah Palin/David Letterman feuds. It's as though the "news" network has forgotten what real news is....

Thursday, June 11, 2009

Nanoscale, the book

No, I have not compiled my blog postings into dead-tree format. Nor have I finished my textbook based on my graduate nanoscale physics course sequence. Instead, I wanted to point out this book, which is a cute volume with lots of computer-rendered pictures of crystal structures and the like. It's an admirable attempt to give the reader a sense of the atomic-scale composition of materials, along with brief, informative, often fun descriptions. While there are a few minor typos that seem to be caused by autocorrection run amok, the book remains entertaining and educational, with very well crafted illustrations. The book has its own website, too.

Tuesday, June 09, 2009

This week in cond-mat

Two papers appeared on the arxiv in the last couple of days concerning the very hot topic of quantum-limited measurement. I'm no expert in the area, but here's a quick summary of the idea.... Anyone who's read anything about quantum mechanics is familiar with the popular "gamma-ray microscope" thought experiment meant to highlight the Heisenberg uncertainty relation. In lay terms, trying to use light to determine the location of a particle with arbitrarily high precision requires, in a simple thought experiment, light of a correspondingly short wavelength. Shorter wavelength = higher energy photons = higher momentum photons = big momentum transfer to the particle. Thus, the more precisely you localize the particle, the less you know about its momentum. This is an adequate handwave for the popular press, but the real situation can be more subtle. Still, in the general problem of quantum measurement, one is often concerned about "back action" - the fact that coupling your system to a detector (thus enabling you to make some kind of measurement of an observable) generally perturbs the equations of motion of the system itself. It turns out, under certain very special circumstances, it is possible to design a measurement and pick observables such that the effect of back action is essentially confined to some variable that you don't care about. The net result in that case is that you can measure your particular observable to higher precision than a simplified uncertainty argument would suggest is possible.

Two groups, those of Keith Schwab at Cal Tech (paper here) and Konrad Lehnert at Boulder/JILA (paper here), have managed to do this type of measurement, looking at the position of a nanoscale mechanical resonator. In both cases, they are able to couple the resonator to a microwave LC resonator in such a way that they can measure the mechanical displacement better than the standard quantum limit. These measurements are very technologically impressive, and they open up the path toward really exciting possibilities, including entanglement of different nanomechanical systems, clever cooling schemes, and true quantum mechanics measurements.