Since I sort of implied a series in the previous post, and I have no better ideas, here’s a look at Thursday’s DAMOP program:
The conference I’m at this week is the annual meeting of the Division of Atomic, Molecular, and Optical Physics of the American Physical Society (which this year is joint with the Canadian version, the Division of Atomic and Molecular Physics and Photon Interactions, or “DAMPΦ.” The Greek letter is a recent addition– as recently as 2001, they were just DAMP.). As the name suggests, this is a meeting covering a wide range of topics, and in some ways is like two or three meetings running in parallel in the same space.
You can see the different threads very clearly if you look at the different sessions in the program. Take, for example, the sessions running Monday morning at 10:30 am (There’s an 8am prize session, which is joint for everybody, so it doesn’t shed much light…):
Session B1 Atomic and Molecular Physics in Early Universe
Chair: Daniel Savin, Columbia University Room: Imperial East
Invited Speakers: Naoki Yoshida, Holger Kreckel, Xavier Urbain, Jonathan Pritchard
Session B2 Ultracold Molecules
Chair: Phil Gould, University of Connecticut Room: Imperial Center
Session B3 Alkaline-Earth Quantum Fluids and Quantum Computing
Chair: Charles Clark, National Institute of Standards and Technology Room: Imperial West
Invited Speakers: T.C. Killian, Ana Maria Rey, Yoshiro Takahashi, Iris Reichenbach
Session B4 Focus Session: Strong Field Alignment and Orientation
Chair: Oliver Gessner, Lawrence Berkeley National Laboratory Room: Regency Ballroom
Invited Speakers: P. Bucksbaum, Maxim Artamonov
Session B5 Photoionization
Chair: William McCurdy, University of California, Davis Room: Arboretum I-III
Session B6 Quantum Information and Quantum Computing
Chair: Dietrich Leibfried, National Institute of Standards and Technology Room: Arboretum IV-V
That’s a wide range of stuff, and it’s worth breaking them down one at a time:
Several people have sent me links to news stories about last week’s Nature paper, “Quantum ground state and single-phonon control of a mechanical resonator.” (It was also presented at the March Meeting, but I didn’t go to that session). This is billed as the first observation of quantum phenomena with a “macroscopic” or “naked eye visible” object.
Of course, there’s a nice bit of irony in a story about quantum effects in a “naked eye visible” object that is accompanied by an image of the object in question taken with a scanning electron microscope. The longest dimension of the object in question is about the thickness of a human hair, which means it technically is naked-eye visible, provided you have pretty good eyes. In a different context, though, something this size would probably be billed as “nanotechnology” (as its smallest dimension is about one micron, or 1000 nanometers).
Still, this is unquestionably the largest thing ever observed in its quantum ground state, so it’s big news. As you can tell by the fact that it’s in Nature. So, what, exactly, have they done, and why is it cool? To vary things up a little, I’ll do this one in Q&A format.
What, exactly, have they done? A group at UCSB has cooled a microfabricated resonator to its quantum ground state. This means that they have removed all the energy that it’s possible to remove from the oscillating mode of the resonator– the only motion left is the zero-point energy that’s impossible to remove. They have also demonstrated the ability to make small excitations of this oscillating mode, both by directly driving it with microwaves, and also by coupling it to a “qubit” fabricated on the same chip.
In quantum mechanics, oscillating objects can only have discrete amounts of energy– the zero-point energy plus 1, 2, 3,… times the energy associated with the oscillation frequency– so the behavior they see is very much unlike a classical oscillator, which has energy that can be continuously varied from zero to whatever you like. What they see here shows signs of the discrete energy values you expect for a quantum oscillator, not a classical one.
So, they, like, took pictures of it moving, or something? I mean, it’s visible, right? Not exactly.
Derek Lowe has a post talking about things biologists should know about medicinal chemistry. It’s a good idea for a post topic, so I’m going to steal it. Not to talk about medicinal chemistry, or biologists, of course, but to talk about my own field, and what everyone– not just scientists– should know about quantum physics. Not just humans, either– even dogs should know this stuff.
1) Quantum physics is real. Probably the hardest quantum idea to accept is the notion of vacuum energy and “virtual particles”– stuff appearing out of empty space, then disappearing again seems almost too weird to credit. And yet the theory predicting virtual particles has been tested to a staggering degree of precision. One number in particular, the “g-factor” for an electron has been measured to be g = 2.00231930436146 Â± 0.00000000000056, and every one of those 14 decimal places agrees with the theoretical prediction.
Every weird effect you hear about in quantum physics is real, and verified by experiment. This is not some airy abstract post-modern theory that doesn’t apply to anything. Quantum effects are absolutely real, and have been confirmed in experiment after experiment.
Today’s Quantum Optics lecture is about quantum computing experiments, and how different types of systems stack up. Quantum computing, as you probably know if you’re reading this blog, is based on building a computer whose “bits” can not only take on “0” and “1” states, but arbitrary superpositions of “0” and “1”. Such a computer would be able to out-perform any classical computer on certain types of problems, and would open the exciting possibility of a windows installation that is both working and hung up at the same time.
There are roughly as many types of proposed quantum computers as there are people working on quantum computation. It’s not clear which of them, if any, will eventually prove to be useful, meaning that this is the perfect subject for a blog poll:
While this is a poll about quantum computing, the machines running the poll are strictly classical, so you can only choose one option.
We report on the design, fabrication, and preliminary testing of a 150 zone array built in a `surface-electrode’ geometry microfabricated on a single substrate. We demonstrate transport of atomic ions between legs of a `Y’-type junction and measure the in-situ heating rates for the ions. The trap design demonstrates use of a basic component design library that can be quickly assembled to form structures optimized for a particular experiment.
At first glance, this isn’t a sexy paper, in that it’s primarily about engineering of components rather than cool quantum effects. Looked at another way, though, this is cool stuff– quantum computing has evolved from the days when it was difficult to do at all, to the point where people are working on modular design for scaling up the devices to a useful size.
Granted, in the history of computation this is much closer to the “nerdy guys at Bell Labs pose with a prototype transistor” than a Quantum iPhone. But it’s still a real shift in the field, and kind of cool to see.
As I understand it, the Physics ArXiv Blog is not affiliated with the people who actually run the Arxiv (Paul Ginsparg et al.). Which is probably good, as I’m never entirely sure how seriously to take the papers they highlight.
Take yesterday’s post, Diamond Challenges for Quantum-Computing Crown, which is about a paper that asks the question Could one make a diamond-based quantum computer?. It’s an interesting idea, and something I wrote about last year, so it seems like a promising topic.
The preprint in question, though, is a little dodgy. It’s indifferently proofread, with all sorts of odd errors in the text, one citation that appears to be duplicated (Neumann et al.), and one of the first references in the paper, to another work by the same author, goes to a line that just says “(the APS paper)”. This isn’t a preprint, it’s a first draft.
Those things by themselves wouldn’t be too bad, but they come in a paper that has some oddities of style and tone that always make me a little nervous. The paper purports to be a detailed analysis of the feasibility of a diamond-computing scheme proposed by one of the authors, and as such, it comes across as less than perfectly objective. And after listing off all the DiVincenzo criteria for making a quantum computer work, they put off discussion of the readout mechanism to a future paper. Given that readout is one of the key elements needed for a quantum computer, it’s a little tough to claim to be doing a useful analysis of the prospects for making a computer without talking about the readout.
So, I’m kind of dubious about this. Not about the idea of diamond-based quantum computation, which does look like it might have promise, but about this specific paper. And, in turn, about the ArXiv blog.
Physics World has a nice news article about a new experimental development in quantum computing, based on a forthcoming paper from the Wineland group at NIST in Boulder. I’d write this up for ResearchBlogging, but it’s still just on the arxiv, and I don’t think they’ve started accepting arxiv papers yet.
The Physics World piece summarizes the key results nicely:
Now, Brad Blakestad and colleagues at the National Institute of Standards and Technology (NIST) in Boulder, Colorado have created a junction in an ion trap in which there is practically no heating. Constructed from laser-machined alumina, it contains 46 gold-coated electrodes surrounding an X-shaped junction. When the researchers apply a series of voltages to the electrodes, ions are encouraged through the junction a little at a time.
The NIST group managed to get ions through the junction with a 99.99% success rate, and with seven orders of magnitude reduced heating than previous trapped ion systems .
The new trap is shown schematically at right, which should give you some idea of the complexity. It’s an impressive technical achievement.
So what’s the big news about this?
I’m not sure what the BBVA Foundation is, but they’ve awarded a Basic Science prize to Ignacio Cirac and Peter Zoller:
The Basic Sciences award in this inaugural edition of the BBVA Foundation Frontiers of Knowledge Awards has been shared by physicists Peter Zoller (Austria, 1952) and Ignacio Cirac (Manresa, 1965), “for their fundamental work on quantum information science”, in the words of the jury chaired by Theodor W. HÃ¤nsch, Nobel Prize in Physics. Zoller and Cirac’s research is opening up vital new avenues for the development of quantum computers, immensely more powerful than those we know today.
[…]Peter Zoller and Ignacio Cirac are regarded as the theoretical physicists of most influence in the areas of cold atoms, quantum optics and quantum information. For more than a decade, their work has broken new ground and opened up new experimental opportunities. At the core of their research is the use of the microscopic world to build quantum computers and communication systems.
Their first major theoretical contribution, dating from 1995, was the description of a theoretical model for a quantum computer. They based their conjectures on what are known as ion traps, in which electrically charged and cooled atoms are trapped by an electric field and manipulated with lasers. Today, this technique still holds out the best promise for quantum computation. In fact some small-scale prototypes of quantum computers have already been built based on the ion trap idea. In the last few years, work done at numerous laboratories has confirmed Zoller and Cirac’s theoretical predictions.
I don’t think I’ve ever met Cirac, but I talked to Zoller a few times when I was doing BEC stuff at Yale. He’s one of those rare people who’s scary smart but also a really nice guy. And the Cirac-Zoller paper really is one of the main launching points for the quantum computing industry, so this is a well deserved award.
My graduate alma mater made some news this week, with a new quantum teleportation experiment in which they “teleport” the state of one ytterbium ion to another ytterbium ion about a meter away. That may not sound like much, but it’s the first time anybody has done this with ions in two completely separate traps, in different vacuum systems. It’s also written up in Physics World, though they spell Chris Monroe’s name wrong throughout.
The paper is coming out in Science, and I may try to write it up for a ResearchBlogging post over the weekend. I may also need to add it to the quantum teleportation chapter of the book-in-progress. A small price to pay for the onward march of science…