Breakthru in quantum computing: salty nanoscale bar magnets!

[daaron]

Three of the big obstacles to quantum computing have been scale (teensy), temperature (cooold), and identifying materials with controllable quantum states. This salt apparently will help researchers learn more about this last problem - perhaps the most pernicious of the three. Here's some of the more telling snippets:

http://www.sciencedaily.com/releases/2012/06/120615103941.htm

The international team of researchers led from the Laboratory for Quantum Magnetism (LQM) in Switzerland and the London Centre for Nanotechnology (LCN), found that the material, a transparent salt, did not suffer from the usual complications of other real magnets, and exploited the fact that its quantum spins -- which are like tiny atomic magnets -- interact according to the rules of large bar magnets. The study is published in Science.
....
The team were able to image all the spins in the special salt, finding that the spins are parallel within pairs of layers, while for adjacent layer pairs, they are antiparallel, as large bar magnets placed adjacent to each other would be. The spin arrangement is called "antiferromagnetic." In contrast, for ferromagnets such as iron, all spins are parallel.

By warming the material to only 0.4 degrees Celsius above the absolute "zero" of temperature where all classical (non-quantum) motion ceases, the team found that the spins lose their order and point in random directions, as iron does when it loses its ferromagnetism when heated to 870 Celsius, much higher than room temperature because of the strong and complex interactions between electron spins in this very common solid.

The team also found that they could achieve the same loss of order by turning on quantum mechanics with an electromagnet containing the salt. Thus, physicists now have a new toy, a collection of tiny bar magnets, which naturally assume an antiferromagnetic configuration and for which they can dial in quantum mechanics at will.
....
"While this may seem esoteric, there are deep connections between what has been achieved here and new types of computers, which also rely on the ability to tune quantum mechanics to solve hard problems, like pattern recognition in images."

[longship]

1. Plus, Bose-Einstein condensates are difficult.

[daaron]

4. True that. It's all very tricksy business.

That's what makes developments in quantum computing so interesting, to me - they're tinkering and hacking at nanoscale, guided by theory into the land of trial-and-error. It's like the heady days of developing I.C.s, except at no stage can any research happen in anyone's garage, this time.

Plus, it means number theory is going to get another boost - say goodbye to RSA, we get to invent new crypto schemes for machines that can REALLY crunch some effing numbers.

[DetlefK]

2. Translation: A minor discovery blown up by big words.

A system that behaves like bar-magnets? Amazing!
No, wait. Mn/Fe(100) behaves the same and works at room temperature.

A Curie-temperature of 0.4K? Amazing!
No, wait. You can reach 1K by a He3-cryostat, 4K by a He4-cryostat, 77K by a nitrogen-cryostat and 293K is room-temperature. The effort to get down to 0.4K removes this experiment light-years from any practical applications.

They can achieve the loss of this order by turning on an electromagnetic field? Amazing!
No, wait. If your magnetic field gets strong enough (I assume some milli-Tesla in this case), it will at some point dominate the Spin-Spin-interaction and force the Spins into a new direction.

[daaron]

3. Not all that minor.

Geez. Give the actual scientists some credit, dude - try to keep some perspective, here. We're just internet nobodies. Discovered any materials with awesome properties that, practically overnight, moved the effort to develop quantum computing forward a decade? No? Then don't be so critical of scientists who did. Sorry if their discovery wasn't world-shaking enough for you. Dismiss it all you want, but then, nobody's reading about your discovery or blowing it up with big words.

To anyone who's actually interested - you can pretty much ignore this arm-chair-physicist's critique. The temperature and scale aren't what's important. The important point is that scientists now have a readily available material that allows a whole host of experiments to be EASILY performed with the potential to teach us what we need to know to move quantum computing out of the single-qubit or two-qubit phase its been stuck for years. The fact that it behaves like a bar magnet means it's highly predictable - that is, controllable - unlike other materials they've mucked about with. So yeah - it might sound like a small discovery, and maybe if one's idea of science is limited to the gooey and biological, it is. Some of us like hard science.

(Man! I never got these weird reactions to groovy science and math on randi.org. First DUers didn't bother reading one article before criticizing it, then this clown decides to dismiss real scientist's discovery with a flood of internet cut-and-paste from their tinfoil hat folder.)

[caraher]

5. Skepticism and excitement are both legitimate responses

Every research group needs to puff up the importance of their work to build/maintain a reputation and keep the funding flowing. That's not cynicism, it's survival, and so every miracle breakthrough warrants substantial critical scrutiny. Over the years there has been a succession of favored physical substrates for quantum computing, and it's exactly these nagging practical issues that knock each one down in turn and drives the search for the Next Big Thing.

But that's not to say there isn't progress. Congratulations are in order for each new avenue discovered and explored. We're building a road map in the dark, and only decades from now will we really be able to see with full clarity which were the blind alleys.

Also, not everyone on DU is an "internet nobody" - many of us do hold advanced degrees in the sciences.

[daaron]

6. Excellent - I was hoping to provoke a thoughtful response -->

with my reference to "internet nobody". Nothing pokes a nerd in the chest like a condescending dismissal of a condescending dismissal. Good to hear that some on DU have adv. degrees. I was starting to wonder, gauging by the quality of the threads, here. Of course, profs can be condescending, too...

On topic: part of why I bothered to post this article is that it's not the miracle substrate, that's not even the intended use of the salt. It interests me because it's a substances that promises to shed light on a more general class of problems, and will hopefully afford new focus to the theoretical end as experimental results come in. Data good.

(Incidentally, my interest is from the mathematical physics wing of R&D. Actually making stuff? Meh. Notsomuch.)

[DetlefK]

7. From nobody to nobody ;-)

Of course they should get some credit (although I can't tell how much). But my issues are legitimate:

1. Why does this discovery get an article, when hardly anyone can tell yet whether it's important or not?

2. Scale and temperature are very important. Quote from you: "...a whole host of experiments to be EASILY performed..."
No experiment at such a low temperature is easy.
And just because they found this particular system, which behaves nice in some ways, doesn't mean, they will find a similar system where this knowledge can be useful. Curie-temperature, energy-bands, spin-polarization, lattice-structure... They could all be different.
My point is: There is no guarantee, any of this research will bear any relevance. (There is almost never a guarantee. ) And I think the article makes a pretty big leap from "we'll see" to "a revolution in quantum-computing".

[daaron]

8. Fair questions.

1. Like you said - funding goes to projects seen as progressing and important, and media helps. I figure in this bizarre era of anti-intellectualism, it doesn't hurt to be a booster, when one doesn't have any further stake in a project. Like me, Science Daily has no stake, so they promote science, written for the lay reader, that they think will spark people's interest and imagination, hopefully counter some of the anti-intellectualism of this bizarre era.

2. It's true what you say - this is a potential breakthrough, not a eureka moment, and the practical obstacles to quantum computing are many, even for experiment. But then, it's not always about the application of the science. Sometimes it's just about the science. I'm just saying ... this is some cool science! Maybe there's no use for it, but really, that's not the whole point, is it? Many a discovery has been made along the way to somewhere else.

[DetlefK]

9. re

1. I don't think anybody funding scientific projects will have his mind swayed either way by this kind of article. And for the goal to induce some scientific curiosity into the readers and society: Maybe the "it's-new-and-barely-understood"-factor is more important to the author/editor than the physics behind interesting examples which are already understood.
Sounds like sensationalism to me.

2. Science for science's sake? To be honest: That's the domain of mad scientists. (A mathematician working on the same abstract proof or theoreme for years, just because it's there...)
But your point is fair: Maybe the experiment will yield something that could be useful far down the road in a totally different discipline.
(For example: neutronium. It's just a bizzare thought-experiment about particle-physics and thermodynamics, until you take into account that neutron-stars are made of this and suddenly it becomes relevant in astronomy.)

[daaron]

10. ok

1. Everybody's a critic. :0

2. Hello? Mathematician, right here. Science for science's sake is all that interests me, and people like me. Far more interesting to tinker with 1000-year old problems on a chalkboard than work with a team of be-goggled engineers assembling someone else's thingamajig for some faceless corporate or gov't agency. Once one has delved into the abstract, it feels so limiting to force every idea into a 'useful' or 'practical' box.

[DetlefK]

12. It all boils down to one question: "So what?"

This begoggled engineer (close enough) prefers the real to the abstract. Why? Because, when everything's finished, one question always remains:
"So what?"
Why did I do this? What has been achieved? What have I changed? Where do I go from here?

Sure the abstract is fascinating and the mathematics of physics are just a scratch on the surface of what's really possible in mathematics (For example, no physicist needs quaternions.), but in the end all abstract problems are equal. They don't give directions, they don't give ideas, they don't give answers. They just are.

[daaron]

13. See for me it comes down to "That's nice."

Quaternions couldn't be a more fitting example - I'm working my way up to a study of contractions of Lie algebras over a quaternion field this summer (prepping for the real thing come fall).

Whereas I have only a passing interest in any given invention or innovation, the mathematics that made it possible continues to interest me. It gets deep, and that's when it get's most interesting. My reaction to the latest gadget is, "That's nice," with a pat on the back. I'm more impressed with Mathsputin, TBH, than any possible application of the his proof of the Poincare' Conjecture (of which, no doubt, there are many).

[caraher]

14. Actually, quaternions can be handy in "real life"

Kuipers' book outlines some very practical examples. They have significant advantages over Euler angles for some applications.

It's awfully hard to know in advance which bits of mathematics will turn out, contrary to all expectation, to contribute something substantial to understanding of "real world" problems. Which is one reason I'm happy we have mathematicians out there exploring the abstract for the sheer adventure of discovery!

[daaron]

15. Yep. Quaternions do have some applications -->

which had no context until long after their discovery. Read an article about it in SciAm.

[Posteritatis]

11. "The domain of mad scientists?" Oy, spare me. (nt)