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Physicists Control the Spin of a Single Electron 98

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."
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Physicists Control the Spin of a Single Electron

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  • It's all over now but the crying, Mother Nature.
  • spin it up (Score:2, Interesting)

    by MrSquirrel ( 976630 )
    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?!).
    • You can measure the field caused by different spin directions.
      • Re:spin it up (Score:5, Informative)

        by MrSquirrel ( 976630 ) on Thursday August 17, 2006 @02:54PM (#15928760)
        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."
        • Re: (Score:1, Informative)

          by Anonymous Coward
          I don't think the electron's spin is the spin you're thinking of. Electrons don't literally physically spin, their spin is a quantum state. There are two possible spins for an electron, and two electrons with different spins can otherwise exist in the same place (ie. the same orbit around an atom). The test they're doing likely tests to see if the two electrons can coexist in one spot, or if one actually "hits" the other.
    • "Hopefully we won't see this applied to spinner rims anytime soon" Those goofy-ass rims are pretty much quantum rims to me anyway...When they spin at a different rate as the wheels I can determine their position or vector, but not both at the same time!
    • 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 differe

      • I know it's not physically spinning, I was just questioning how they measured it since you measure the electric field to determine the "spin"... and they were suppossedly spinning it with an electrical field... so I was just wondering how they knew that they were actually spinning it, not just saying "when we apply an electric field, it spins"... because if they tried to measure the electric field from the electron, the electric field they were using to spin it would be picked up so they would say "see, it
  • Stop That (Score:5, Funny)

    by ReidMaynard ( 161608 ) on Thursday August 17, 2006 @02:43PM (#15928659) Homepage
    It makes the electrons dizzy.
    • It makes the electrons dizzy.

      Furthermore, it makes the molecule wobbly, and then, due to the Uncertainty Principle, they can no longer find the damn thing...

  • by RomSteady ( 533144 ) on Thursday August 17, 2006 @02:44PM (#15928679) Homepage Journal
    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)
  • They are able to rotate the axis to every possible direction
    I thought there were, like, only 2 of those?
    • What, you live in a one-dimentional world?

      Or did you think they meant change the direction of the rotation? They mean changing the direction of the axis itself.
  • Amazing. (Score:3, Interesting)

    by radarsat1 ( 786772 ) on Thursday August 17, 2006 @02:49PM (#15928723) Homepage
    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?)
    • Re: (Score:3, Insightful)

      Speed isn't important yet: First you have to actually do it, then you worry about speed. First, though, you make a prototype that works. They don't actually have that yet (just parts, of which this is one), so they don't know what the potential speed bottlenecks are. (Or what might be the best way to handle them.)
    • Re: (Score:2, Insightful)

      by jpardey ( 569633 )
      I think it has something to do with the "Pauli Exclusion Principle [wikipedia.org]," which actually explains the structure of the periodic table. Something to do with no two electrons being able to share the same quantum state and position.

      So I think it is only limited by the speed of the equipment, not the process.
    • by mn_ace ( 947870 )
      Check out http://qt.tn.tudelft.nl/research/spinqubits/ [tudelft.nl]. They posted some timing numbers there. They talk about "Real-time detection" of a single electron tunneling with a speed of about 8us.
  • Researchers (Score:5, Funny)

    by Anonymous Coward on Thursday August 17, 2006 @02:52PM (#15928742)

    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?
    • Never mind data transfer, what about distributed computing with quantum computers?
      • Re: (Score:2, Funny)

        by JGuru42 ( 140509 )
        I almost expect to see a Beowulf cluster comment coming on.......
        • I must be loosing my touch; I didn't even think of that. Where'd my geekiness go? Oh, wait, that's good thing.
      • Never mind data transfer, what about distributed computing with quantum computers?

        The answer to your question is, believe it or not, in NP. The size of the input is 4000 times the size of the question "0=0?", so I just have to run it through my deterministic machine for a little while. I'll let you know when it's finished...

        In the meantime, somebody please correct me if I'm wrong (and I'm sure you will), but you shouldn't actually need to distribute a problem across multiple quantum computers - the

        • Anyway, I'll get back to you as soon as my SAT-solver terminates with the correct answer....

          I, alas, have only a PSAT-solver. Sigh.

          • well, at least yours finishes in polytime... the truly important question is, can we overclock a quantum computer?
      • Depends on the memory controller. If you know the address, you can't determine the data, if you read the data you don't know how to address it. Unless the controller is in the 5th Dimension, because we will always know that Aquarious is the offset.
        • What are you getting at? That a RAM bank would be affected by Heisenberg?
          I don't think so, mainly because they just have to measure local fields (I think).
    • by Zenaku ( 821866 )
      I became very interested in the whole "instantaneous data transfer at any distance idea" a while back and spent some time reading equations that are WAY beyond my meager mind's ability to grasp. But I think, if I understood the basics correctly, entanglement doesn't actually allow for this. Here's a wikipedia link: No-communication Theorem [wikipedia.org]

      Anybody out there with a PhD in Quantum Information Theory, please feel free to explain it to me.

      • yeah, you can't use it to send information because you cant control its state while its entagled with another electron (at a distance). once you affect it in any way, it's no longer entangled. it's just that, when you first measure it, you know that what you've measured is related to the state of the other electron.
    • Wait, if you actually change one of the electrons' spins, doesn't that mean that they decohere and are no longer entangled?
  • by Anonymous Coward
    The Acorn [old-computers.com] Electron [wikipedia.org] 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.
  • by Anonymous Coward
    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 the "sloppy" term for angular momentum in an electron is "spin", what is your problem with people using that term?
      • The objection is to comments (from the summary) like: "They are able to rotate the axis to every possible direction...." The submitter clearly is thinking of a spinning ball, but that is incorrect. Calling the angular momentum of an electron "spin" is one thing, going a step further and talking as if it's really spinning is just wrong.
        • While the spin is governed by a more complex set of equations, the spin vector is used frequently when communicating the direction of axis of spin. The wording is perfectly fine for the audience and is used often by physicists when describing this attribute of particles to non-physicists.
  • If god wanted us to control the spin of electrons, he would put handles on them !!!!
  • The ability to completely control spin? I thought Bill O'Reilly [billoreilly.com] could already do that...

    v.m
  • The Wikipedia article about Quantum Entanglement [wikipedia.org] 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?
    • 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 th
      • by RedDirt ( 3122 ) *
        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. =)
    • How about, "if it were that easy, we would have already done it"?

      It's not as if physicists collectively have large bets out on the inability to communicate or travel faster than light; indeed, for the person who manages it it's probably a guaranteed Nobel prize and quite possibly public acclaim that physics hasn't seen since Einstein.

      If you want a more technical explanation, go Google for it. I'm tired of explaining it to people who don't want to believe it and use their mighty high-school-dropout physics s
      • Re: (Score:3, Informative)

        by MindStalker ( 22827 )
        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...
        • Tell that to the scientists at IBM and various universities that have been constructing limited quantum computing devices using that very parlor trick.
          • I think my question was more on the lines of communication via entanglement. Either way this was mid 90s so its possible that at the time it seemed useless.
      • by RedDirt ( 3122 ) *
        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. =)

        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 /. (which is why I phrased the qu
    • by Ryan C. ( 159039 )
      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 c
      • by brunes69 ( 86786 )

        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.

        True, according to this once you set the spin of an electron you destory the entanglement.

        but not until *after* that new state was reflected in the other entangled electron, correct? If thi sis the case, can't you ship a billion billion entangled electrons from X to y, and set the spin of ones at X to send a message to Y? Sure, you can only use each entanglement once

        • The problam with that is that when the people at y try to check whether the spin has been set, they will set it themselves and not know if it was set before by the people at X.
      • by RedDirt ( 3122 ) *
        Thank you! My brain neither imploded nor did I further devolve into a gibbering baboon. It is a good day, I have learned something new. =)
  • From the Article at http://www.tudelft.nl/live/pagina.jsp?id=4b3e55d0- 1a34-4388-b3ca-acbe48c87696&lang=en [tudelft.nl]:

    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

    • "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.
    • Re: (Score:2, Interesting)

      by brunascle ( 994197 )
      the article doesnt go into enough detail, but i dont think it's claiming they they're controlling or measuring all the axes at the same time, but just that they're not limited to a single axis. that would seem to make sense, if they're planning to use an electron for a single bit (up=1, down=0).

      i have some other questions though: for one thing, are they realling claiming they can "lock up" an electron? doesnt that imply that they know both its location and momentum (stationary) at the same time?
  • I thought the spin coming from the Republicrats and Democans was bad enough. Why do scientists have to jump on the spin bandwagon?
  • That's nothing. I once saw a guy spinning 20 plates on sticks -- all at one time!

    tone
  • 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
  • by ClassicComposer ( 916856 ) on Thursday August 17, 2006 @04:52PM (#15929915) Journal
    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.
  • Somewhere in my armchair physics wrangling, I read that you can't identify an individual electron, as they're all identical, and magic markers don't stick to them.

    How did these guys know they had a single electron, and it was always the same electron?

  • Surely this is the last step in making a fully function quantum computer!

    We should have one in only a year or two!

    </sarcasm>
  • 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).
    • by zyl0x ( 987342 )
      In order to transfer information between two points, the behaviour of quantum particles have to be predictable when observed. The problem is that scientists have no idea what the spin on those particles will be until the exact second they're measured. All that does is define what the spin on the entangled particle will end up being. This is, of course, only one of many current difficulties with quantum physics and entanglement.
  • 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
  • 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.

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