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Physicists Control the Spin of a Single Electron
jeeb writes "Researchers of the Delft University of Technology and the Foundation for Fundamental Research on Matter have succeeded for the first time in controlling the spin of a single electron in a nanostructure. They are able to rotate the axis to every possible direction and to record it accordingly. This achievement makes it possible to use the electron's spin as a 'quantum bit,' the basis of a (still theoretical) future quantum computer. The researchers have published this scientific breakthrough in the August 17, 2006 edition of Nature."
It makes the electrons dizzy.
-- www.globaltics.net
Political discussion for a new world
First request from the electron was for more funding for science programs.
If that isn't controlled spin, I don't know what is. (grin)
RomSteady - I came, I saw, I tested. GamerTag: RomSteady / http://www.romsteady.net
This is really incredible news.
One thing -- there is no mention in the article about how _long_ it takes to read the electron's spin. It would be interesting to know. It says they simply have to see whether the two electrons can be placed next to each other. How is this done and how long does it take? I would assume for a quantum computer to be useable this method must be able to be executed quite quickly. (Maybe the speed isn't important?)
The researchers working on this are doing so to obtain their PhDs. Presumably they will henceforth be known as "spin doctors".
I know they can measure the field easily... but after reading most of the full article, I wasn't sure how they would measure it while still controlling the rotation (since they were spinning the electron using magnetic fields). Then I finished reading the whole article (after posting of course) and got my answer: "Their approach was to lock up a second electron in another quantum dot alongside the first one and to use it to read out the spin direction of the first electron."
A computer once beat me at chess, but it was no match for me at kick boxing.
I almost expect to see a Beowulf cluster comment coming on.......
Folks, electron spin is NOT like the spinning of a ball in "the real world." The electron is not "rotating" per se. From wiki:
"Such particles and the spin of quantum mechanical systems ("particle spin") possesses several unusual or non-classical features, and for such systems, spin angular momentum cannot be associated with rotation but instead refers only to the presence of angular momentum."
jfs
The only thing worse than a Democrat is a Republican.
The ability to completely control spin? I thought Bill O'Reilly could already do that...
v.m
I have a "Zero Policy" tolerance.
*/
An electron does not only have an electrical charge, but it also behaves like an ultrasmall magnet. This is caused by the spinning of the electron around its axis, also called 'spin'.
Electrons do not move about their axis, the spin is a measure of the magnetic angular momentum, if memory serves from quantum physics. Also, no, electrons do not only have two directions to spin, their spin can be in any direction, but only measured spin up or spin down with respect to a single axis at any time. This is based upon the fact that in the Schrödinger equation the operators don't commute for the eigan functions. Put simply, that means that if you measure the spin once in the z direction and obtain an answer, then in the y, and again in the z, you will end up with a different value.
I would also like to know how they are controlling the spin in every possible direction, and effectively measuring it. Because unless the laws of physics have changed, they can still only measure spin up or spin down.
I once asked a FSU physics researcher (who used to hangout at a coffee house and regularly beat my ass in chess) about quantum entangement. He told me essentially it was a parlor trick and to forget about it. /Don't know the point of this story, really...
How do we know it was scientists in our universe that was able to make the electron spin? Maybe it is another team in a parallel universe that did it and we are just seeing the results. I feel bad for the other universes where the experiment failed :-/
OK, we can't really explain the whole entaglement thing without using big words and wave equations, but here's a very close analogy:
Say you have two balls, one red, and one blue. You blindly put them into two identical boxes, and ship one to Pluto. After that's done, you open the box here on Earth and see that it's red. You instantly know the color of the ball on Pluto is blue. What good does that do you? Nothing.
The quantum entaglement is almost the same, except that the balls don't finalize their color until you look at one. But the information is just as useless.
The question of This + Quantum Entaglement is also flawed, you can't have both. If you set the spin of one, you've destroyed the entaglement.
-Ryan C.
That's not precisely true. Of course, some ways of recording the spin will change it, and there are theoretical restrictions, but in theory it is possible to observe the spin without changing it. For example, measuring the spin in a particular axis as up or down will set the quantum state to a pure state of up or down in that axis. If it was already in that same pure state, observing it wouldn't change it. Of course, observing the spin in a particular axis sets it into a pure state, so if it weren't already in a pure state, or if it were in a pure state along a different axis, then you're right that an observation would change the spin.
David
No, information still cannot be transmitted, as other posters have mentioned. They can control the spin of one of the entangled electrons, but once they do, the electrons are no longer entangled. Science-fiction authors are fond of using "entanglement" to defeat speed of light limitations on communication, but it doesn't actually work (at least, not according to current theories, which are unchanged by this experiment).
David