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Slow Light = Fast Computing

Posted by Zonk on Fri Jan 19, 2007 12:45 PM
from the yay-light-beams dept.
Sci-Fi Science Technology
yohaas writes "The Washington Post is reporting that scientists have been able to slow the speed of light while still maintaining its ability to transmit information. The researchers have even developed a way to 'tune' the process, modulating how fast or slow the light goes within controlled circumstances. From the article: 'Scientists said yesterday that they had achieved a long-sought goal of slowing waves of light to a relatively leisurely pace and using those harnessed pulses to store an image. Physicists said the new approach to taming light could hasten the arrival of a futuristic era in which computers and other devices will process information on optical beams instead of with electricity, which for all its spark is still cumbersome compared with light.'"
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  • Ahem. (Score:5, Funny)

    by Hawthorne01 (575586) on Friday January 19 2007, @12:48PM (#17683500)
    We don't say "slow light" anymore. We say "Luminescentally Challenged".

  • Future performance whores will brag... (Score:5, Funny)

    by Anonymous Coward on Friday January 19 2007, @12:48PM (#17683504)
    ...in terms of how small their underclock of c is.
  • worst pun ever

  • Hothouse? (Score:4, Interesting)

    by LordPhantom (763327) on Friday January 19 2007, @12:56PM (#17683648)
    Well...ok, but...

    Howell and his colleagues created a four-inch-long chamber filled with cesium gas heated to about 212 degrees Fahrenheit.

    I'm guessing that this isn't going to be coming to the desktop anytime soon.... even a major datacenter might balk at the energy costs of doing this versus a parallel traditional solution.
    • So it turns out that a slashdot title is a gross oversimplification/mischaracterization of an issue? Say it ain't so!
    • We already have a household appliance that can reach much higher temperatures than that. Just hook your computer up to your kitchen stove and you're good to go!

        • Re:Why not? (Score:4, Insightful)

          by ceoyoyo (59147) on Friday January 19 2007, @01:58PM (#17684652)
          Why's that? 212F is just the boiling point of water, heating up cesium gas isn't all that hard and you wouldn't need to maintain a very large volume at that temperature. A regular processor will quite rapidly get more than hot enough if you don't spend lots of energy cooling it.

    • Just line the chamber with Pentiums.

    • It will have to come to the desktop since we will be running short on electrons soon. Photons, storing bits in single electrons, ... Why do you think all this is being researched these days? They don't want to admit it, but you just have to read between the lines.
  • We are already worried about data center power usage. I'm pretty sure it costs a bit to have cesium gas hanging around the data center.

  • It should be called.... (Score:3, Insightful)

    by julesh (229690) on Friday January 19 2007, @01:02PM (#17683764)
    Slow glass [technovelgy.com]

  • Meanwhile, scientists at.. (Score:5, Funny)

    by LM741N (258038) on Friday January 19 2007, @01:03PM (#17683790)
    UC Santa Cruz have achieved a 1/1000 slowdown of light by passing a beam through a cloud of marijuana smoke.

    • Re: (Score:3, Insightful)

      by drinkypoo (153816)
      UC Santa Cruz have achieved a 1/1000 slowdown of light by passing a beam through a cloud of marijuana smoke.

      The results were invalidated, however, when it was pointed out that the atmosphere of Santa Cruz is typically a cloud of marijuana smoke, and the control experiment failed to take this into account.

    • UC Santa Cruz have achieved a 1/1000 slowdown of light by passing a beam through a cloud of marijuana smoke.

      Yeah, but I hear they've been doing that since the 60's. :-P

  • The future is now! (tm) (Score:5, Insightful)

    by Itninja (937614) on Friday January 19 2007, @01:10PM (#17683876) Homepage
    Physicists said the new approach to taming light could hasten the arrival of a futuristic era
    I hate statements like this. How does a 'futuristic era' arrive? Correct me if I'm wrong, but isn't it impossible to hasten the arrival of the future? And when the future does indeed arrive, will it not then be simply 'the present'?
    • Clearly slowig down light speeds up time, G'ah.

      It also changegs the behavour in gravity, but you guys have relized that yet.

      -- Futuristic era man.

    • Physicists said the new approach to taming light could hasten the arrival of a futuristic era
      I hate statements like this. How does a 'futuristic era' arrive? Correct me if I'm wrong, but isn't it impossible to hasten the arrival of the future? And when the future does indeed arrive, will it not then be simply 'the present'?
      Not if you can get Doctor Emmett Brown to pomp your DeLorean.

    • Re:The future is now! (tm) (Score:5, Funny)

      by Atzanteol (99067) on Friday January 19 2007, @02:16PM (#17684980) Homepage

      And when the future does indeed arrive, will it not then be simply 'the present'?

      Dark Helmet: What the hell am I looking at?!
      Colonel Sandurz: Now. You're looking at now, sir. Everything that is happening now is happening now.
      DH: What happened to then?
      CS: We passed it.
      DH: When?
      CS: Just now. We're at now now.
      DH: Go back to then!
      CS: When?
      DH: Now!
      CS: Now?
      DH: Now!
      CS: We can't!
      DH: Why?
      CS: We missed it.
      DH: When?
      CS: Just now.
      DH: When will then be now?
      CS: Soon.

    • Re: (Score:3, Informative)

      by julesh (229690)
      The key difference is that IBM's approach didn't actually slow the light down, but rather channeled it through rather long conduits. You couldn't store an image that way, because the light was constrained to move in a single dimension inside a cavity. This can store images, because it is completely three dimensional.

  • Moo (Score:4, Interesting)

    by Chacham (981) on Friday January 19 2007, @01:11PM (#17683914) Homepage Journal
    FTA:

    Howell and his colleagues created a four-inch-long chamber filled with cesium gas heated to about 212 degrees Fahrenheit. When they sent pulses of laser light through that gas, the cesium atoms put the brakes on the leading edge of that wave, creating a photonic traffic jam.
    So Cesium slows things down....

    Yet, this artcle [nytimes.com] which was reported on Slashot here [slashdot.org], says

    In the most striking of the new experiments a pulse of light that enters a transparent chamber filled with specially prepared cesium gas is pushed to speeds of 300 times the normal speed of light. That is so fast that, under these peculiar circumstances, the main part of the pulse exits the far side of the chamber even before it enters at the near side.
    I'm a bit confused. Does Cesium speed thing up or slow things down?
    • I'm a bit confused. Does Cesium speed thing up or slow things down?

      I'm not surprised you're confused. You've read an article on weird quantum effects in the popular press as if anything that was described in it were true. No, light does not travel faster than c in the experiment described. It does do bizarre stuff, though.

    • Re:Moo (Score:5, Informative)

      by exp(pi*sqrt(163)) (613870) on Friday January 19 2007, @01:33PM (#17684248) Journal
      The latter article is about phase velocity. Phase velocity is the speed at which the individual peaks and valleys of the signal appear to travel. But peaks and valleys aren't actual 'things' and you can't transmit information using them. (See here [netspace.net.au].) This latest story is about the rate at which you can transmit information, so it's about group velocity [wikipedia.org].

      Despite the fact that the theory was worked out more well over a century ago, almost every modern pop science story about manipulating the speed of light leaves out these crucial points.

      • To strengthen this arguement, the product of the phase velocity and the group velocity is the speed of light squared. Or alteratively, the speed of light is the geometric mean of the phase velocity and the group velocity. So passing the light through Cesium must speed up the phase velocity by the same ratio that it speeds up the group velocity.

        Somewhat off topic... The last page of Physical Review is accelerating down the book shelf at a rate limited by the ability of the physics community to publish pap

  • Call me when they slow down darkness. (Score:5, Funny)

    by bad_fx (493443) on Friday January 19 2007, @01:20PM (#17684022) Journal
    "No matter how fast light travels, it finds the darkness has always got there first, and is waiting for it."

    • "No matter how fast light travels, it finds the darkness has always got there first, and is waiting for it."
      Goldstaff, Sorcerer of Light, I will have my vengeance!
  • Three guesses what that image was...

  • A much better scientific description here (Score:3, Informative)

    by viking80 (697716) on Friday January 19 2007, @01:27PM (#17684144) Journal
    Here is a half decade old article that describes the process well. It also uses units such as nm and Kelvin instead of thigs like "seven times around the earth" and "about 450 degrees below zero"

    http://www.physics.hku.hk/~tboyce/sf/topics/lightf reeze/lightfreeze.html [physics.hku.hk]
  • Is the light really being slowed down here, or are the photons just taking the scenic route to their destination instead of going in a straight line?
  • (no, not slow Windows--I have that already)

    Could this be used to make a window to look out of that would show me what happened five minutes ago?

  • It's been done already. Light slows down whenever it passes through anything. It only manages to get up to 299 792 458 ms-1 in a perfect vacuum. Even air slows it a little bit.

    Whenever a beam of light moves from one medium, eg. air, to another, eg. glass, its speed changes. If it enters on the skew, so the speed of one side of the beam changes before the other side, then the beam changes direction; just like a vehicle with a binding brake, it swings towards the side that slows down first. When it comes out of the glass back into air, it speeds up again and changes direction again, exactly the reverse way to what would have happened on the way in (since a beam of light always follows the same path, whichever end it's shining from); unless it's travelling at such an angle there's no way it could ever have got to be travelling in that direction by going through the surface and slowing down a bit sooner on one side than the other. In which case it simply bounces off like a pool ball hitting the cushion and tries to escape somewhere else. This is how fibre optics work.

    It also means that when you blast a pulse of light into one end of a long fibre optic, some of it comes straight along the middle and out of the other end at the speed of light in whatever stuff the fibre is made out of; but some of it takes a longer journey, bouncing off the walls, and some of it bounces more times than others. So you get a longer pulse at the far end than you originally put in (and dimmer, since the same amount of energy is now being spread over more time). If you're sending many pulses at a high enough frequency, there comes a point when the first pulse hasn't finished arriving at the far end before the second pulse goes in, and the receiver won't be able to tell which is which. Also, if the fibre goes through a bend, sometimes some light that you thought was going to bounce off the walls actually strikes at such an angle as it can get out. With modern, highly flexible materials, this can actually happen without you bending the fibre enough to break it.

    If you want maximum bandwidth out of your fibre, you have to take these phenomena into account. You can buy cheap acrylic fibre, with LEDs and phototransistors that screw-couple onto it; these can often be used for RS232 links with no additional components, using the transmitter to light the LED and the phototransistor to pull down the voltage at the receiver, but you'll be lucky to get more than 9600 baud through such a link. With just some simple signal conditioning, you can make it run much faster.
    • It's been done already. Light slows down whenever it passes through anything. It only manages to get up to 299 792 458 ms-1 in a perfect vacuum. Even air slows it a little bit.

      They slowed it to 17m/s (which had been done years ago, the not losing information part might be new?). That's a little different than what air manages...

  • ...their computer will never be as fast as Hex.

    +++Out of Cheese Error+++ +++Please Reboot Universe+++ +++Redo from Start+++

  • Implications for cameras (Score:4, Interesting)

    by pHatidic (163975) on Friday January 19 2007, @04:14PM (#17687384) Homepage
    Does this mean we could take, say, one second worth of light coming into a camera and then slow it down so that we could get a picture at a super high shutter speed at any point during that one second period?

    • Re: (Score:3, Informative)

      by ThanatosMinor (1046978)
      Perhaps they meant only one photon at a time. The interference pattern that light creates on a screen does not depend on whether you send one photon through at a time or an entire beam.

    • One possible method for that... (Score:5, Interesting)

      by tpjunkie (911544) on Friday January 19 2007, @01:05PM (#17683820) Journal
      Is that the stencil is actually a fourier transform hologram, printed out on film. This would look like a pattern of seemingly random dots, but a focused beam of light would resolve the hologram image, even if sent photon by photon over time on a detector.

    • Re:*cough*bullsheet*cough* (Score:5, Informative)

      by julesh (229690) on Friday January 19 2007, @01:16PM (#17683974)
      There's no way a single photon makes a stencil image.

      There's a well-known effect that when you perform Young's double-slit experiment with single photons, the interference patterns still remain. If a single photon can interfere with itself, I'm sure it can make an image.

        • Re:Interference (Score:4, Interesting)

          by Lord Crc (151920) on Friday January 19 2007, @05:02PM (#17688200)
          It's not a single photon interfering with itself.

          The interference pattern will occur even if there's only one photon in the apparatus at a time (that is, a photon hits the detector before a new one is generated).

          See this page [princeton.edu] for instance.
    • I don't know why you say this. Unless you're thinking that a photon is a particle and concieving of that particle as a speck of dust of grain of sand. Photons, like electrons, don't always act like a particles. Sometimes they act like waves.

      • Re: (Score:3, Informative)

        by mhall119 (1035984)
        Yes, but when they contact something, the act like a particle. Even in a dual slit experiment, a single photon will produce only a single contact, not a pattern. The pattern arises from the non-uniform distribution of multiple single photon contacts. The original comment's confusion was thinking that the hologram was produced by a single photon, rather than a succession of individual photons.

    • Re: (Score:2, Funny)

      by Anonymous Coward
      Rest assured we will. :)

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