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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's all over now but the crying, Mother Nature.
I may make you feel, but I can't make you think.
So they can control the spin of a single electron? That's pretty neat, definitely sounds like they're making progress on a quantum level of getting closer to the reality of a quantum computer. I'd like to know how they know the electron is spinning -- I'm not questioning their work, I just can't think of a reasonable way to measure how you were controlling the spin.
Hopefully we won't see this applied to spinner rims anytime soon (actually, we wouldn't be able to see it at all, so who cares?!).
A computer once beat me at chess, but it was no match for me at kick boxing.
It makes the electrons dizzy.
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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)
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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 understand the breakthrough in terms of quantum computing but how about in long range data transfer?
Can't we use this to finally test the idea of entangled electrons sharing the same spin?
The Acorn Electron was a bulky piece of kit, so controlling the spin of such unwieldy moulded plastic is a great achievement. I wonder if they did it with the Plus 1 or Plus 3 expansions attached ...
It does beg the question of why they were spinning it in the first place, rather than playing Chuckie Egg, but the minds of scientists are quite different from yours or mine, and we should just sit back and applaud the achievement.
Read the press release then repeat after me boys and girls: electrons do not spin; electrons are point (or point-like) particles with **intrisic** angular mommentum. Sometimes we sloppily refer to the intrinsic AM as "spin" but that has nothing to to with an electron spinning around some axis. You'd a thunk the folks at TUDelft would have read the press release before allowing such drivel to be disseminated.
Is it ironic that the crypto word for this post is "nature"?
If god wanted us to control the spin of electrons, he would put handles on them !!!!
Read radical news here
The ability to completely control spin? I thought Bill O'Reilly could already do that...
v.m
I have a "Zero Policy" tolerance.
*/
"Is this a computer for ants!" -- Zoolander
The Wikipedia article about Quantum Entanglement says no, but the explanation seems to be: "of course it's not FTL because we can only verify the communication at lightspeed."
Umm, okay. Can some big-brain 'splain it to me using small words so I'll be sure to understand?
James
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 thought the spin coming from the Republicrats and Democans was bad enough. Why do scientists have to jump on the spin bandwagon?
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Say that we have two entangled electrons which are lightyears apart. Say that you are next to one of them, and you test its spin. Let's say that it's spinning "up". By the property of simple entanglement, you know for a fact that the sister particle, when tested, will have to be in the "down" state. So you know something about a particle lightyears away instantaneously.
Now, given that you have a message that you want to send to the other end. This means that somehow you have to control what the person on the far side of the electron pair sees. However, you really have no control over the process. The chances that you saw "up" or "down" on your local electron were completely random. Once the detection has been made, there's no way to further influence the result. Thus, no information has been transmitted.
So there I was, juggling apples and small animals, when I accidentally bit into the wrong one...
"I would also like to know how they are controlling the spin in every possible direction"
They've either contracted with him or James Carville.
Where were you when the voynix came?
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...
For once I try to be one of the gang, and I get modded redundant? I spot a relatively new story with an obvious joke that _Somebody_ was going to jump on and I figure, what the hay, be part of the crowd for once. If not me, then it would have been one of you and don't tell me otherwise. And for my contribution I get modded down and redundant! Probably somebody with mod points jealous that I took his precious line. this whole internet is so unfair! Now what, grammar nazis?
Tell that to the scientists at IBM and various universities that have been constructing limited quantum computing devices using that very parlor trick.
That's nothing. I once saw a guy spinning 20 plates on sticks -- all at one time!
tone
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I might have the Bohr:Rutherford version of the atom stuck in my head; but is there any kind of measurable force that opposes the 'flip' necessary in this experiment (like a gyroscopic effect)? Do all atoms have an "up" and "down" orientation?
Does the nucleus of the atom (protons, neutrons) spin in the same direction as the electrons (similar to our Sun & planets)?
How does the whole 'electron cloud' theory even make it possible to detect the spin? (I thought that these quantum measurments affected the reults just by trying to measure them?!)
ok, help! My head is starting to hurt.
"The price good men pay for indifference to public affairs is to be ruled by evil men." ~Plato (427-347 BC)
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 :-/
Fox News have been able to do that for years.
How did these guys know they had a single electron, and it was always the same electron?
Actually, the electron is not "spinning". When we talk about spin it's an analogy.
The terminology comes from two types of angular momentum in classical physics. One is "orbital" angular momentum, which comes about when an object is moving relative to some other point, like the earth going around the sun. The other kind is "spin" angular momentum, which is the rotation of an object about its centre of mass (like the earth spinning on its axis). The total angular momentum is the sum of these two different kinds.
The whole reason we can talk about the Earth "spinning" is that it has a structure -- it's made of other, smaller things, and the smaller things move around the axis. As far as we know, that isn't true for the electron -- it seems to be a true point particle so far. And yet, it has intrinsic angular momentum, which can be detected experimentally!
In the case of the earth, its spin angular momentum is really just the sum of all the orbital angular momenta of all the little bits of dirt that make it up, orbiting around the axis. Maybe that's true for the electron, and the fact that it has spin is a clue that it's made up of other particles?
Turns out the answer is no. A well known result of quantum mechanics is that any orbital angular momentum (i.e. the usual kind) can only occur in integer multiples of some lowest angular momentum (kind of like how electric charge can only come in multiples of the charge on the electron). If the electron's spin were due to other particles that made up the electron, then its magnitude would be some integer multiple of that unit of angular momentum. Turns out that it's exactly half that lowest value! So it's a different kind of angular momentum altogether, and the electron doesn't really "spin".
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.
Surely this is the last step in making a fully function quantum computer!
We should have one in only a year or two!
</sarcasm>
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
Does that mean we can read the spin of an entangled particle? because, if it is so, then it means we can have instant communication throughout the universe, in a way even better than portraited in sci-fi (subspace comms in Star Trek etc).
When they say 'every direction possible', are we talking extra-dimensional spinning? IE, depending on your favorite flavor of string theory and/or atomic level structure, was this electron oscilating/spinning only in our visible dimensions, or was this experiment applicable to the other 4,5,8,125,2^8 dimensions(depending on your favorite number of dimensions)...Seems like a horrible waste of effeciency if the electron jumps and loses its spin. On second thought, I have no idea how we would verify this at all - any thoughts?
If I mod you up, it doesn't necessarily mean I agree with what you've said, sorry.
How awesome is this yet anouther step for quantum computers. One by one they are solving the technical difficulties of using particles in their quantum state to accomplish computing. Given the amazing possibilites of quantum computers, I get exicted everytime they take anouther step foward.
They call me....Tim??!
Well, I'll admit that after I worked my butt off to get a B in calc, I decided that instead of CompSci I'd rather go with InfoSci and learn all about PowerPunt instead of hard stuff like math. =)
/. (which is why I phrased the question the way I did) but I did get a very accessible response.
That said, I am very interested in this sort of thing but stuff that I google about is either written for folks with more background than I have or are written by quacks who want to sell me a quantum cure for athlete's foot. *shrug* Not that I expected a lot of difference here on
James
Aha! I was under the (mistaken) impression that the two electrons were "paired" somehow (tied by cosmic string? =P) and that altering the spin of one would, by virtue of the entanglement, force a change in the other. Thank you for clarifying that. =)
James