Monday, March 28, 2011

Quantum Entanglement, Diamonds, and New Information Storage Tech

"Diamond Could Store Quantum Information"
Devin Powell, Science News, via Tech News, Discovery News (March 28, 2011)

" * By manipulating atoms inside diamonds, scientists have developed a new way to store information.
" * The technique could lead to quantum computers capable of solving problems beyond the reach of today's technology.

"Could be that diamonds are a geek's best friend.

"Scientists have developed a new way to manipulate atoms inside diamond crystals so that they store information long enough to function as quantum memory, which encodes information not as the 0s and 1s crunched by conventional computers but in states that are both 0 and 1 at the same time. Physicists use such quantum data to send information securely, and hope to eventually build quantum computers capable of solving problems beyond the reach of today's technology.

"For those developing this quantum memory, the perfect diamonds don't come from Tiffany & Co. -- or Harry Winston, for that matter. Impurities are the key to the technology.

" 'Oddly enough, perfection may not be the way to go,' said David Awschalom of the University of California, Santa Barbara. 'We want to build in defects.'...

The article implies that the defects - anomalies in the diamond crystal's lattice - would probably involve nitrogen, a frequently-found impurity in diamonds.

The non-carbon atoms are important because - "...Several years ago, scientists learned how to change the spin of such electrons using microwave energy and put them to work as quantum bits, or qubits...."

The new technique links the spin of an electron to a nitrogen atom's nucleus. The transfer involves magnetic fields, and it's fast: "...about 100 nanoseconds, comparable to how long it takes to store information on a stick of RAM."

Back to the article, again: "...The technique has 'a fidelity of 85 to 95 percent,' Awschalom said March 22 in Dallas at a meeting for the American Physical Society.

"In contrast to some other quantum systems under development, which require temperatures close to absolute zero, this diamond memory works at room temperature. The spins inside the diamond can be both changed and measured by shining laser light into the diamond. This could make diamond an attractive material for scientists developing nanophotonic systems designed to move and store information in packets of light.

"Unlike a diamond itself, this quantum memory isn't forever. But it lasts for a very long time by quantum standards. The nuclear spin remains coherent for more than a millisecond, with the potential to improve to seconds....

"...Sebastian Loth, a physicist at IBM's Almaden Research Center in San Jose, Calif. [said], 'If you have a lifetime of milliseconds, that lets you do millions of operations.'

"In addition to stability, diamond may also overcome another hurdle that has faced quantum computing -- it can be scaled up to larger sizes. In a paper published last year in Nano Letters, Awschalom developed a technique for creating customizable patterns of nitrogen atoms inside a diamond, using lasers to implant thousands of atoms in a grid...."

A thousand atoms in a grid is impressive: but the scaling doesn't, apparently, stop there. Transmitting quantum information is possible, by connecting/entangling qubits. Problem is, entanglement seems to work up to a distance of kilometers: which is huge on the atomic scale, but pretty much useless for a network that extends much beyond one city.

That may not be such a serious limitation, though. The article ends with this: "...Quantum repeaters could potentially use small chips of diamond to catch, store and retransmit this information to extend the range, enabling quantum networks to work over much longer distances."

The principle sounds pretty much like the way we transmit radio and television signals today - and that's almost another topic.

For an article with phrases like "fidelity of 85 to 95 percent" that says why some folks are interested in which way electrons spin - it's pretty interesting. In the Lemming's opinion. Your experience may vary.

The Still Sell Vacuum Tubes

The Lemming checked: and sure enough, some outfits are still selling vacuum tubes.

That's not very surprising. Old technologies are sometimes useful for particular situations - or someone may just like doing things the old-fashioned way. One of the Lemming's extended family was a flint knapper - and that's another topic.

It's been an exciting half-century. The Lemming remembers when it was obvious that computers would be huge things, occupying entire buildings and consuming vast amounts of power.

Then the transistor stopped being a laboratory curiosity, and started being part of little boxes attached to the ears of adolescents.

This hasn't, the Lemming suspects, been a particularly comfortable era for folks who'd just as soon that their great-grandfather's way of life be indistinguishable from their own - and for whom "innovation" is the reckless practice of trying a new sort of food. Or wearing a shirt of a different color.

And the Lemming's getting off-topic again.

Somewhat-related posts:

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