APS: So long.
Well things are winding up, and I’m exhausted. It’s been a fascinating meeting, and I hope that you’ve enjoyed our blog! See you around, like a doughnut.
Nature Newsblog
Nature Newsblog
March 20, 2009
APS: Quantum cryptography is just plain cool
The meeting is wrapping up, and I’m getting ready to pack up here in Pittsburgh, but not before getting myself to a talk by Andrew Hammond a vice president at MagiQ Technologies. MagiQ is in the business of quantum key distribution, a process that uses quantum entanglement to ensure the secrecy of encrypted data.
This was all very academic when I wrote about it just a few years ago, but what was evident in Hammond’s talk is just how practical it’s becoming. According to Hammond, MagiQ’s system is now capable of refreshing a secure key at a rate of once a second. Considering that involves entangling two photons, sending one of them along a piece of optical fibre, and reading them both out when it arrives, that’s pretty darn impressive. And Hammond says there technology is constantly improving: they’re even working towards developing a PCI card that could fit inside a desktop computer.
The economic downturn has been bad for business, he admitted (banks thought to be among MagiQ’s relatively short list of highly confidential clients). But, he says, that parts of the federal government are now deploying their systems on a large scale. Assuming the economic downturn doesn’t turn into a meltdown, it sounds like quantum cryptography is here to stay.
APS: What to get the physicist with everything?
As I was zipping back and forth between sessions, I kept passing the APS’s legislative booth, a row of computers where physicists could sit down to write their members of congress. In past years, the letters have pleaded for better funding for the physical sciences, which rarely receive big spending boosts.
But this year things are different. Stimulus is the buzzword and the Treasury’s purse is wide open. For example, the US Department of Energy‘s office of science is receiving a 20% increase to it‘s US$4 billion dollar budget, and that‘s before the additional money contained in the US$787 stimulus package. Obama’s 2010 budget, unveiled earlier this month, is also promising substantial increases.
I asked Brian Mosley (right), a legislative assistant for the APS, what they could possibly want after such a bumper year. “Nothing’s guaranteed,” Mosley says nervously. The stimulus money is “a one shot thing,” and as the 2010 budget winds its way through congress, “there will be a lot of competing interests.” Physicists will need to make the case that what’s good for them is good for the economy.
They’ve done a pretty decent job of getting there voice heard this week: Mosley tells me that 1434 of the 7500 physicists at the meeting have written their legislators. Given that probably around half or more of the people here aren’t US citizens, that’s an impressive turnout.
March 19, 2009
APS: When is a solid not a solid? When it's a supersolid.
posted on behalf of Ed Gerstner
One of the advantages of being just one editor in an editorial team is that when something comes along that you just don't get, you can always try to pass responsibility for handling submissions on that topic to someone else. For me, supersolids was one of those things. They're fluids, superfluids in fact, but they have characteristics of a solid. What?!? Try as I might, I couldn't get my head around it.
But when I picked up a buzz about new evidence of supersolidity in an entirely new system, I figured it was time to push through this particular mental block.
The new results come from Dan Stamper-Kurn at UC Berkeley, who works on Bose-Einstein condensates (BEC) of ultracold gases. The atoms in a Bose-Einstein condensate don't exist at well defined positions like the atoms in a solid crystal. Each and every atom in a BEC spreads itself over the entire volume of the condensate, which can be tens of micrometres wide and hundreds of micrometres long. In the profoundest sense, a BEC has no atomic structure — not even the amorphous structure of the atoms that jostle about in a conventional liquid. This is one of the things that puts the 'super' in a superfluid.
And yet when Stamper-Kurn's group look at variations in the magnetic polarization of a trapped ultracold quantum gas of rubidium atoms (by shining light through it), they see sees a handful of microscopic blobs that order themselves around each other like the beginnings of a crystal (see the figure 2 of their preprint). It's not a typical crystal of course, the blobs are not atoms or groups of atoms forming in localized clusters in the gas — the density of the gas remains smooth and homogeneous. But its magnetic behaviour makes it look like a crystal. And crystalization is the signature of a solid.
And it's as simple as that. A supersolid is a thing that has the properties of both a superfluid — in this case a quantum gas that has no material structure — and a solid — in this case crystalline order amongst its magnetic domains.
What does this all mean? I'll tell you. I don't know. But finally I can see what it looks like.
image: arXiv:0901.3800v1
APS UPDATE: iron pnictides iron-based superconductors. WTF?!
So I woke up this morning to find an e-mail from David Singh that makes iron pnictides compounds even more interesting. Apparently, last year, Hsu et al. replaced arsenic with selenium and found that their new compound could superconduct at 8K. Now Singh tells me that other groups are reporting temperatures of up to 37K at high pressures for some FeSe compounds (there's plenty more on arXiv, so don't take that link as a conclusive lit search). Se compounds are chalcogenides, so he thinks they can’t rightly be called iron pnictides anymore.
Iron-based superconductors is a little bland. Anybody got a better name?
March 18, 2009
APS: Iron pnictides. WTF?
Pretty much anything with iron pnictides in the title is guaranteed to draw a crowd at this year’s meeting. I snapped this picture at a random session this morning, but others have been so rammed that it’s been hard to get in the door. Iron pnictides are the hottest new superconductor, so it’s not surprising that they’re getting a lot of attention. But I’ve been to a few of these talks, and I’m going to be frank--if you’re not an expert it’s very hard to follow. And I know what you’re thinking (particularly if you’re one of my editors): This guy’s a senior reporter with Nature and you’re telling me he can’t understand this stuff?
Well before you get on my case, it turns out I’m in good company. At a reception last night I sat down with David Singh, a theorist at Oak Ridge National Laboratory, and he told me that nobody really understands the pnictides. We’ve published a few papers recently suggesting that, unlike the cuprates (the other main class of high-temperature superconductors) pnictides seem to facilitate electron flow in three dimensions. But there’s still a lot of questions about what induces this superconductivity. “It’s new, it’s different and people don’t understand it,” Singh says.
So WTF? What’s all the excitement at this meeting about? Well Singh tells me that there’s a couple of things worth noting. First, people are synthesizing better quality pnictide samples. In particular, they’ve got single crystal samples that are of very high purity and thus yield better data. The second thing that’s happening is that groups are synthesizing a bunch of different compounds and checking them out. I sat in on a talk by Hai-Hu Wen of the National Laboratory for Superconductivity in Beijing, where he discussed the latest results for pnictide compounds that use iridium, rhodium and cobalt to name a few.
These compounds all superconduct in a similar range of temperatures, so there’s no big breakthrough as yet. But Singh says that they’ll help us to better understand what’s going on, and you never know, there could be a surprise. The main point, he says, is that after decades of working on just the cuprates, the community now has another high-temperature model to work with. “Nature has given us two different routes to high-Tc,” he says.
APS: Nanotubes as filters
I just got out of a pretty cool talk about filtering water with carbon nanotubes. Apparently because the walls of the tubes are so smooth, water molecules can flow super fast through them. On top of that, the rims of the tubes are charged and can therefore reject unwanted ions.
Olgica Bakajin of Lawrence Livermore National Laboratory had some impressive results on display. She fashioned crude filters by growing carbon nanotubes on a silicon surface. She embedded the tubes in silicon nitride and shaved down the compound until a few of the tubes' tops were open. As the image on the right reveals, it’s not the prettiest technique (only those tubes in yellow are actually open). But it works! Her filter allows lots of water through and rejects ions at rates compatible with commercial products.
The immediate application would be for water softening, a process by which ions are removed from water in order to prevent crusty build-up (as an American living in the UK I can attest that there’s plenty of room for improvement on that front). The good thing about the tubes is that they would be higher-throughput and thus more energy efficient than commercial products. And Bakajin tells me that if they can get the diameter a little smaller, they might even be able to desalinate seawater...
credit: Y. Wang/LLNL
APS: No limits imaging
Not many of the rules of physics are actually set in stone, but the diffraction limit is one of them. In imaging terms, the limit determines the smallest discernable feature you can make out through a microscope. It’s etched on this memorial to the 19th century German physicist Ernst Abbe, located in Jena (right).
But as the Bible proves, rules set in stone are made for breaking, and yesterday we heard from two clever physicists who’d beaten the diffraction limit. W.E. Moerner of Stanford University in California looked at fluorescing proteins in cells with a very dim light. Each cell gave off a little pinprick which could then be pinpointed using computer software, and in this way, Moerner could perform in situ imaging of individual proteins. Stefan Hell of the Max Planck Institute for Biophysical Chemistry in Gottingen had another scheme: He used two superimposed beams of light to make sure that only the protein directly under his microscope lit up. Both of these methods were able to image molecules just nanometers in size.
Of course, they’re not the only ones--there are plenty of non-optical systems that can resolve nanometer scale features (scanning-tunneling microscopes for example). But the advantage of these systems is that they can provide in situ images of biological molecules. It’s all sexy enough that our sister pub, Nature Methods, named these and related techniques as its method of the year. Check out their cool video to learn more:
Image: S. Hell
March 17, 2009
APS: Black holes in the lab
It’s not really the sort of thing that you’d expect to find at a meeting which is mainly about materials, but I heard an interesting talk about recreating black hole jets in the laboratory today. For those unfamiliar with what I‘m talking about, swirling material around the top of a black hole often gets ejected in a long narrow stream. The process is complex and guided largely by the behavior of the hot, ionized gas in the jet, known as plasma.
Paul Bellan of Caltech in Pasadena, California wanted to get a better idea of how it all worked, so he built his own (right). Bellan’s black hole isn’t a hole at all: it’s two circular metal plates, one inside the other. By putting an enormous voltage difference across the plates, he can ionize gas above their surface and, albeit briefly, recreate the giant jets of black holes. He’s used his experiments to model how magnetic fields create giant jets. His conclusion? “It’s kind of like squeezing a toothpaste tube.”
Credit: P. Bellan
APS: Wet and wild physics
As I mentioned earlier, you can find just about anything at the March meeting. And yesterday I found out why the tops of your feet get soaked if you’re walking across even a thin layer of water (in say, a wet parking lot). Jake Fontana of Kent State University has studied the problem in detail, using a high speed camera. With each step, a plume of water is flung from the underside of the shoe to the top of the foot. By Fontana’s calculations about 250 cubic millimeters land on your shoe with each step.
It may not sound like much, but over the course of a kilometer, that means your shoe gets half-a-liter of water dumped on it. Some studies just beg the question why? So I asked. “It’s just something that bugged us,” replied Fontana.
credit: J. Fontana
APS: The batteries of tomorrow today
Every session that’s got something to do with either solar cells or batteries is jammed packed, and it’s not hard to imagine why: The US Department of Energy (DOE) is going to be throwing a lot of money at renewable energy in the weeks and months to come.
At a press conference yesterday, we got a little update on various battery technologies that could have a big impact in the not-too-distant future. First up was Mohit Singh of SEEO, Inc. and his former supervisor Nitash Balsara of the University of California at Berkeley. SEEO is working on replacing the liquid electrolyte that is used to transport lithium ions in many batteries with more rigid polymers. These dry batteries would have some important advantages over what’s in your laptop. First is safety, the rigid polymers are less volatile than their liquid brethren, and so they are less likely to overheat and catch fire. Additionally, they would not degrade over time, meaning that your computer battery could keep its charge over years of use. Finally, they would allow batteries to operate at higher voltages, and thus higher charges.
The second speaker was Hiroyuki Nishide, of Waseda University in Tokyo. He updated us on advances in a plastic battery that could store charge in organic molecules. This can be used to create lightweight flexible batteries that could store energy in more imaginative ways than our current generation of batteries (The plastic shell of your laptop, for example, could work as the battery). Additionally, these batteries, like the one we reported on last week, are also able to charge and discharge in seconds.
Like a lot of recent advances in batteries, neither of these technologies are quite ready for prime time. Singh’s cells still require ultra long charging times to fill up with juice, and Nishide’s polymers don’t have the energy density needed to be used commercially. But they’re yet another sign that the battery business is booming.
March 16, 2009
APS Physics in Senegal: There isn’t much…
As anyone who spends a day at an APS conference can tell you, physics is a global affair. I’ve heard talks by Koreans, Japanese, Germans, Australians and Americans today (among others). But one region which is consistently underrepresented at the APS is Africa.
I dropped in on a session about physics in Africa and heard a case study: Senegal. Ndeye Arame Boye-Faye, a physicist at the University Cheikh Anta Diop, Dakar laid out the stats for physics in the country, and it became immediately clear that the problem (as is so often is the case) comes down to money. Senegal’s GDP is a meager US$13.9 billion, and of that just .05% (around US$7 million) goes to research. The nation’s main grants system, known as Fonds d’Impulsion de la Recherché Scientifique et Technique (FIRST), doles out US$700,000 in grants each year. That’s right, $700,000 for the entire country--there are single labs in the West that can suck up a grant that size.
Boye-Faye was quite low-key about it all: “You can see that it’s not a very big budget,” she said modestly. She hopes that the country can get a little help from France and other developed nations to boost its research efforts.
APS: Welcome to Pittsburgh
Greetings from the American Physical Society's March Meeting. This year it's being held in Pittsburgh, home to Andy Warhol, and for this week, around 7,500 physicists.
This meeting is an unwieldy beast. Researchers in fields from superconductors, to nanotech, to biophysics are all here talking about their work. There's even a talk on watching paint dry, and a session on crumpling things into balls (which actually looks pretty interesting).
Stay tuned...
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