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Physicists Watch Individual Electrons Flow 120

SG writes "Physicists at the Tokyo Institute of Technology have developed the world's most sensitive ammeter yet. The device allows current to be measured at the attoampere level and is expected to be of use in nanoelectronics, calibration devices, quantum computation and biology."
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Physicists Watch Individual Electrons Flow

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  • Picture (Score:5, Funny)

    by Anonymous Coward on Tuesday June 20, 2006 @09:41PM (#15573468)
    Here's a picture of the ammeter in action [newportharbor.us].
  • Shweet (Score:1, Interesting)

    by Joebert ( 946227 )
    According to the team, combining the ammeter with a device that converts photons or electron-spins to electronic charges could also lead to the development of sensitive detectors for light or magnetic fields.

    Would be nice if this could mean gigapixel cameras & the answer to the age old question of ghosts.
  • So... (Score:5, Interesting)

    by RyanFenton ( 230700 ) on Tuesday June 20, 2006 @09:50PM (#15573501)
    Would it have to change the flow by measuring it? How much by pure quantum "observation" effects?

    As a non-phyisics grad (Computer science), I'm wondering.

    Ryan Fenton
    • Re:So... (Score:5, Insightful)

      by MindStalker ( 22827 ) <mindstalker&gmail,com> on Tuesday June 20, 2006 @10:00PM (#15573536) Journal
      If you read this is simply a device that channels electrons into a single file channel then measures the movement through the channel. Akin to putting a dam in water then putting a very small pipe in the dam and putting a meter on that. What you are ultimatly changing is the amount of electrons that get through, so I'm guessing to measure a current of any size you would have to have millions or more of these???
    • Re:So... (Score:5, Informative)

      by agentcdog ( 885108 ) on Wednesday June 21, 2006 @03:05AM (#15574422)
      Apparantly, it uses quantum effects to do its measurements. There are two very small electron "cages" and the electron must tunnel across from one "quantum dot" (their words) to the other. In answer to your question ALL ammeters affect the systems that they measure. Mostly it isn't a big deal because they have very low resistance. There are some situations where it is very difficult to measure current. One scenario is when the resistance of the circuit is very small. The other is when the current is very small. The reason it is so hard to measure small currents is that there is thermal movements of electrons in the metal. When you amplify the current it amplifies the noise. There are various ways of getting around this. According to TFA this technique introduces very little noise, which allows it to measure very small currents. The whole heisenberg effect is more a matter of indeterminacy for individual particles. The scale of the measurements appear to be big enough that the sum of the individual particles should be an accurate representation of the flow. If anyone reading the article can add clarity, I would welcome it.
  • Cool! (Score:5, Funny)

    by Crazyscottie ( 947072 ) on Tuesday June 20, 2006 @09:51PM (#15573507)
    So now ol' Ben Franklin can finally see which direction electrons really flow!
    • Re:Cool! (Score:3, Informative)

      by ookabooka ( 731013 )
      Electrons do move from negative to positive, but the "current" as defined by Ohm's Law [wikipedia.org] does "flow" from positive to negative. Way back when they didnt know which direction stuff moved, so they defined it as moving from positive to negative for the sake of their mathematical calculations. Right hand rule, left hand rule. . bah semantics.
      • It's funny that the same mistake was made with the Earth. The North pole is actually near the Earth's magnetic _south_ pole. Except we call the magnetic south pole the magnetic North pole, but it's a south pole.....

      • Electrons in a normal conductor don't really don't move that fast anyway. Something like a slow walking pace.
  • Current, tunneling ? (Score:5, Interesting)

    by karvind ( 833059 ) <karvind@NOspam.gmail.com> on Tuesday June 20, 2006 @09:52PM (#15573510) Journal
    I RTFA and it employs two quantum dots to distinguish the direction of the flow. As the article mentions: scientists already know how count single electrons travelling through an individual quantum dot

    My question is if I want to measure current (assume an ideal current source) then I will hook it up to this new invention. The mechanism of current in this new measuring device is quantum tunneling. Is there any reason that the current source in question employs the same mechanism. It may still be conventional drift-diffusion with very very low fields (and probably very low mobility). Now when I interface it with this double-quantum device, does the change in mechanism ensures current quantity ? If answer yes, what is the intutive answer. I can understand current continuity when it is drift and diffusion.

  • Nanoelectronics, calibration devices, quantum computation.... and the world's smallest abaci.
  • I can think of a lot of smart, witty, even sarcastic jokes about this article... but this is truly a 'Wow' moment if you fully understand the implications of this.
  • by vldragon ( 981127 ) on Tuesday June 20, 2006 @10:05PM (#15573551)
    Before you read any of the article and just say the headline: "Physicists Watch Individual Electrons Flow" did anyone think of a bunch of guys in white lab coats looking down at a table with money in their fists betting on electron races? Because I did... And boy was it disturbing... Gambling physicists can be very rude. (At least the ones in my head are)
  • So does this mean... (Score:3, Interesting)

    by Audent ( 35893 ) <(moc.stiucsibevoli) (ta) (tnedua)> on Tuesday June 20, 2006 @10:14PM (#15573585) Homepage
    that we can finally see just what happens with that light box experiment with waves/particles of light?

    Someone with a clue help me out here. Does this mean we'll get a definitive answer on how a single particle of light can actually be in two places at once?
    • At least not until you get into wave or string theory stuff and that's based on the very thing you're trying to look at so not exactly going back to basics.
    • This won't help because light behaves as both a particle and a wave, depending on how you are observing it.
      From Wikipedia [wikipedia.org]:

      when the particle could be passing through either of the two slits, it will actually pass through both, and so an interference pattern results. But if the particle is detected at one of the two slits, then it can no longer be passing through both - it must exist at one or the other, and so no interference pattern appears.

    • Nope. Because it's only in two places at once if you're not looking at it.
    • Try this http://www.vega.org.uk/video/subseries/8 [vega.org.uk]. If you don't have the bandwidth you can buy them from the University of Auckland.
    • by Savantissimo ( 893682 ) on Tuesday June 20, 2006 @11:06PM (#15573740) Journal
      We already know the answer to that. "Wave propagation" and "particle interaction" are redundant expressions; "wave interaction" and "particle propagation" are oxymoronic. "Waves" and "particles" are not entities or properties but rather behaviors - wave propagation is the constant or increasing lack of information about the quantum relative to the observer/instrument/indicator and particle interaction is the creation or transmission of information relative to the observer/instrument/indicator.

      Single particle interactions are never in two places at once. The information that originally was one quantum may be distributed across space as it propagates as a wave or distributed across ensembles of different quanta in entangled states, but the interactions (particles) themselves are always strictly local.
      • by Memnos ( 937795 ) on Wednesday June 21, 2006 @07:06AM (#15574864) Journal
        I think that a plausible explanation (or at least one that deserves more research) is the Pilot Wave theory proposed by de Broglie-Bohm. See http://plato.stanford.edu/entries/qm-bohm/ [stanford.edu] and other numerous sites for a discusion of this proposition. (Disclaimer: I have never been a big fan of the Copenhagen Interpetation.) Nonetheless, I feel that an explanation which obviates the "observer problem" and explains decoherence merits looking at.
        • by hawkfish ( 8978 )
          You link looks broken, but this [washington.edu] description (where it is called the "Guide Wave Interpretation") points out that it is incompatible with Bell's inequality.

          For a pretty thorough discussion of various interpretations, have a look at the containing article [washington.edu].
        • As another non-fan of the Copenhagen Interpretation, I suggest that you try looking at the Many Worlds Interpretation. It has an elegant explanation of the observer problem: Different versions of the observer observe different results. The results seem random to these observers because they all occur, and different observers see different things. This interpretation is beautifully elegant once you really understand it.

          Basically, the Many Worlds interpretation simplifies to the Copenhagen interpretation if y
    • by fulvioc ( 983942 ) on Tuesday June 20, 2006 @11:43PM (#15573853) Homepage
      You're talking about the double-slit experiment or two-slit experiment consisting of letting light diffract through two slits producing fringes on a screen. These fringes or interference patterns have light and dark regions corresponding to where the light waves have constructively and destructively interfered. The experiment can also be performed with a beam of electrons or atoms, showing similar interference patterns; this is taken as evidence of the "wave-particle duality" predicted by quantum physics. Note, however, that a double-slit experiment can also be performed with water waves in a ripple tank; the explanation of the observed wave phenomena does not require quantum mechanics in any way. The phenomenon is quantum mechanical only when quantum particles - such as atoms, electrons, or photons - manifest as waves. I doubt the machine will be able to distinguish whether one electron goes through one slit and/or vice/versa. Remember, observing the behavior of these particles causes the wave pattern to collapse. They're almost there, but they're very far off at the same time.
      • You misunderstand what the double slit experiment involves.
        In the double slit experiment, the light or particle source that is used is turned down so low that at any given time, there is no more than 1 particle going through the barrier.
        This cannot be replicated in a ripple tank. A ripple tank, or any kind of macro scale wave inherently cannot produce the same result as the double slit experiment because it can not be proven that any individual particle is the wave is interfering with itself.
        • In the double slit experiment, the light or particle source that is used is turned down so low that at any given time, there is no more than 1 particle going through the barrier.

          Also, isn't it that the collapse of the wave function depends on what you put after the barrier?

          That is, if you put a single particle detector at one of the slits (or a very sensitive screen), you will get "pings" that eventually "build up" to show the interference pattern fringing. However, if you put a particle detector in front o

      • My education on these matters is sadly limited (for now), but I'm not quite so sure they're "almost there", or if they'll ever be "there" for that matter.

        Any observation of a quantum particle requires some sort of interaction with that particle. Once you interact with the particle, the wave function collapses.

        Unless I'm horribly mistaken, this breakthrough only allows us to observe particles with less interaction to them. Regardless of this fact, any observation imlies a collapse of the wave function.
        • If sunlight is replaced with a light source that is capable of producing just one photon at a time, and the screen is sensitive enough to detect a single photon, This experiment can, in theory, be performed one photon at a time -- with identical results. If either slit is covered, the individual photons hitting the screen, over time, create a pattern with a single peak. But if both slits are left open, the pattern of photons hitting the screen, over time, again becomes a series of light and dark fringes. T
    • Swap the word 'particle' for 'packet' and it's often easier to understand. It appears as though it's a partical because they are of fixed units (1, 2, but never 1.5). So in effect, it's a 'packet' of energy... the energy travels in packets of set sizes, so it looks like particles, but it's not. The packet of energy may spread out as it travels, but it's still the same packet.

  • Am I the only one to notice that that would be full of TITs ?!?!

    Sigh...I need to get some soon.
  • and the rest of us are forced to watch GOLF on TV.
  • more info (Score:3, Informative)

    by Anonymous Coward on Tuesday June 20, 2006 @10:34PM (#15573650)
  • Great. (Score:1, Insightful)

    by s800 ( 940543 )
    Except that charge is what's moving, not necessarily electrons.
    • Re:Great. (Score:1, Informative)

      by Anonymous Coward
      Except that charge is what's moving, not necessarily electrons.

      I think you'll find that the majority of charge carriers are in fact electrons.
      • but let's not forget those minority carriers. they're present, even in your lamp cord.
        • generally minority carriers means the less common of conduction band electrons or valance band holes, but holes aren't physical items they are just representative of missing electrons (a good analogy for hole current is moving your overdraft from one bank to another, its still money thats moving between banks).

          the only things that carry charge in a normal conductor are electrons, ions can also do it but only really in soloutions afaict.
  • by this great guy ( 922511 ) on Tuesday June 20, 2006 @10:48PM (#15573695)
    For an unknow reason, their device automatically falls into sleep mode after having counted too many electrons.
  • but can they hustle?
  • Okay, sure it may be a really sensative ammeter, but sensativity isn't everything. I'd have two questions.

    Is it auto ranging? Because that makes things a lot easier/faster

    Will it shut itself off automatically, even if you forget to turn the dial back to "off" because I gotta tell ya...I've killed more batteries that way. I mean, it's so annoying, you take out your meter and it's dead because you didn't turn the dial back. UG!
  • I always thought it was a waste to have all those electrons flow just to represent a '1' instead of a '0'.

    Now they only need one electron - cool :)
    • You don't even need the electron. You can have EM waves without electrons.
      • ..but then what would they use this new device for?
      • by Anonymous Coward
        The whole business about what is being observed is somewhat academic. We don't really know that any of these things exist as such, but only that the world seems to behave as if they did. We have no way to perceive reality directly, but only to probe how she behaves indirectly.

        And that's good, because it means that we can throw out old theories with impunity once better ones are devised. If we were to ever observe the TRUTH, we would no longer have the freedom to do that, and it would be the end of Scienc
  • by Anonymous Coward
    Finally!

    Something I can measure it with!

    Thank you, God!

    Muhaha!
    It's alive! It's alive!
  • What would be the gain-bandwidth for a current amplifier built with this technology?
  • When you get down to zepto and yocto, that's when things really start happening!
  • How exactly is this "watching"?
  • by fahrbot-bot ( 874524 ) on Wednesday June 21, 2006 @02:59AM (#15574410)
    Physicists Watch Individual Electrons Flow

    ...paint dry.

    Ahh, the wayward electron...

    An Electron's Longings [netfunny.com]
    The electron
    at the edge of the valence band
    said:

    I stand upon the edge
    Condemned by fate's cruel hand
    To lie in a state of perpetual freeze
    With energy lacking to do a trapeze
    Across to freedom's higher land

    There are many who have risen beyond
    Coulombic forces. They blisfully exist
    Unshelled. Their orbitals know no bond.
    With carefree abandon they diffuse and drift.

    Will no photon shine a light ?
    Will no dopant lend a hand ?
    To conquer Fermi's improbable height
    To leap into the conduction band !
  • What a waste of money. The other night I drank one $7 bottle of sake and I was able to see individual quarks moving.
  • I can remember from my Lab days (boy, has it been really 20 years?!) a Burr-Brown amm-meter that had an electron-count mode where it would display "electrons per second" (actually unit-charges) instead of femto-amperes. Sure, it only counted in about 100-electron steps, but I think that's fair enough... :-)

Whenever people agree with me, I always think I must be wrong. - Oscar Wilde

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