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Science

Light Stopped, Held And Re-emitted By A Crystal 366

Posted by timothy from the dark-crystal dept.
nherc writes: "An article in Nature talks about an incredible new crystal that can actual stop and hold light to be later emitted. It's mentioned light has previously been "slowed" by super cooled gases, but this certainly blows that away. They mention this could be a major step towards quantum computing."
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Light Stopped, Held And Re-emitted By A Crystal More

Light Stopped, Held And Re-emitted By A Crystal

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  • Uerm.. correct me if I'm wrong, but doesn't glow-in-the-dark stuff "stop and hold light to be later emitted"?
    • Um.. you are wrong, so I'll correct you. "Glow in the dark" stuff glows because a chemical reaction is happening, and generating light. This is something completely different. These guys actually brought light to a hault, so that a pulse of light stopped in the crystal


      • These guys actually brought light to a hault, so that a pulse of light stopped in the crystal


        Well, no. It's hard to tell from the lack of detail in the Nature article, but from it's description, it sounds like this material can be made to absorb light, and somehow another laser is later used to extract it. (Same wavelength and phase?) It's not like there are photons standing still somewhere.
      • If you want to bring a pulse of light to a halt, just put something black in its path... :-p
      • Um.. you are wrong, so I'll correct you. "Glow in the dark" stuff glows because a chemical reaction is happening

        These guys actually brought light to a hault

        Um.. you are wrong, so I'll correct you. Glow in the dark [wisc.edu] stuff glows because its electrons are easy to bump into higher orbitals (by absorbing photons), then slowly come back down (by emitting other photons).

        These guys have a special supercooled substance that -- guess what -- absorbs photons into electron orbitals, then emits other photons! It's the same damn thing, except that in this case the photons coming out are the same color and have the same direction as the ones that went in.
    • Um. Yes, It stores energy, then releases it later. But, this sounds like it actually holds the photons and releases them later. Or at least that's what the submission infers.

      The article seems a bit sketchy and makes a connection that I don't think is 100% valid, how can this possibly relate to quantum computing? This has nothing to do with electron spin. It has alot to do with trapping photons, then later releasing them by exciting the atoms.

      My guess is that the fundamental difference is the wavelength of the light emitted when it is released is the same as the wavelength of the light that was stored in the crystal.

      • Re:Magical Crystal = Glow In The Dark Stuff? (Score:5, Informative)

        by br0ck ( 237309 ) on Tuesday January 08, 2002 @05:31PM (#2806134)
        how can this possibly relate to quantum computing?

        From http://www.sciam.com/2001/0701issue/0701hau.html [sciam.com]

        "Another application for slow and stopped light could be quantum computers, in which the usual definite 1's and 0's are replaced with quantum superpositions of 1's and 0's called qubits. Such computers, if they can be built, would be able to solve certain problems that would take an ordinary computer an enormously long time. Two broad categories of qubits exist: those that stay in one place and interact with one another readily (such as quantum states of atoms) and those that travel rapidly from place to place (photons) but are difficult to make interact in the ways needed in a quantum computer. The slow-light system, by transforming flying photons into stationary dark state patterns and back, provides a robust way to convert between these types of qubits, a process that could be essential for building large-scale quantum computers. We can imagine imprinting two pulses in the same atom cloud, allowing the atoms to interact, and then reading out the result by generating new output light pulses."

      • Re:Magical Crystal = Glow In The Dark Stuff? (Score:4, Informative)

        by GreyPoopon ( 411036 ) <[gpoopon] [at] [gmail.com]> on Tuesday January 08, 2002 @05:38PM (#2806187)
        But, this sounds like it actually holds the photons and releases them later. Or at least that's what the submission infers.

        Based on the article, it appears more like the complete energy from the photons is absorbed by the atoms. The photons can then be emitted later by changing the intensity of the laser that is causing the atoms to hold onto it. I don't see this as really trapping light. It looks more to me like the energy from the "holding laser" plus the energy from the photons manages to push the electrons to a higher valence level and leave them there, even when the incoming photon supply is turned off. Then I would suspect that lowering the intensity of the holding laser would allow the electrons to drop to a less excited state and thus release the energy in the form of photons. It really sounds just like a fluorescent light except that you now have control over when the photons are actually generated by the excited atoms.

        Feel free to correct me vigorously. I haven't thought about this kind of stuff in earnest for more than 15 years.

      • Since this is not a spontaneous process, the wavelength of the emitted photon can be identical to that of the original photon without violating conservation of energy. In fact, all the characteristics of the photon--wavelength, polarization, phase, etc.-- are stored in the crystal and can be recovered, so that the emitted photon is identical to the original.
    • Sort of, but not exactly... To my knowledge, you can't control when the phosphorescent material will re-emit the light that came in. Nor can you guarantee anything about polarization, etc. of the outcoming light - it's not the same light coming out that went in.

      OK,
      - B

    • I'm not sure why you got voted funny, but basically, you're right. From the article:

      A light pulse that is brought to a standstill is not destroyed. The atoms 'remember' it, so the pulse can be regenerated by changing the intensity of the coupling laser to allow the atoms to re-emit photons - the particles of which light is composed.

      That's pretty clear, if you understand that "light pulse" isn't quite the same as "light" or "photon." This is, of course, a tremendous scientific and technological accomplishment. In terms of basic physics, though, it's roughly similar to glow-in-the-dark paint, or the behavior of a neon or fluorescent bulb, for that matter. The photon is destroyed, but I presume the amplitudes of the atom get stuck in a state where they are exactly the same as if they were entangled with a photon just like it. So, when you fire a laser into it, you get a result that is exactly the same as if you fired a laser at the atom when the original photon was coming at it, and the interference between the amplitude of the laser and that of the atom therefore produces an amplitude just like the one of the original photon, so you see it. Really, really cool trick, but the trickiness is getting the amplitudes stuck in such a way that they keep so much information, not really in stopping light.

    • Uerm.. correct me if I'm wrong, but doesn't glow-in-the-dark stuff "stop and hold light to be later emitted"?

      Glow in the dark stuff is made up of phosphors - similar material as what's in your CRT monitor. Phosphors emit visible light when excited.

      The phosphors in your monitor are delicately excited by the electron gun in the back. The phosphors in glow in the dark stuff are excited en masse by normal light.

      See How Stuff Works [howstuffworks.com] for more details.

      J.J.

  • whats next (Score:3, Interesting)

    by emptybody ( 12341 ) on Tuesday January 08, 2002 @05:10PM (#2805894) Homepage Journal
    optical ram that is a crystal matrix that actually holds the image and energy?

    • Re:whats next (Score:2, Interesting)

      by ianaverage ( 168691 )
      I have a question...

      Does anyone know how long the crystal is able to hold this energy/information and/or what kind of energy is required to perform this experiment? It does not say it in this article, and I dont recall it being mentioned in the SciAm article (although that was quite a while ago that I read it).

  • constant speed of light (Score:5, Funny)

    by totallygeek ( 263191 ) <sellis@totallygeek.com> on Tuesday January 08, 2002 @05:10PM (#2805896) Homepage
    E=0?


    No, really, I know light speed changes. c is just for light in a vacuum... This is really neat stuff, and I hope this becomes a leap forward in understanding quantum mechanics.

    • Light speed doesn't change (Score:5, Informative)

      by UberQwerty ( 86791 ) on Tuesday January 08, 2002 @05:45PM (#2806248) Homepage Journal
      Only average lightspeed changes. The speed of light (photons - same speed as all massless particles) is always c (about 300kk in m/s). However, the light can be delayed. When a photon hits an atom, it usually transfers its energy to an electron, which jumps to a higher orbital. The electron then nearly instantly drops down to its old orbital and gives off the energy in the form of (guess what) a photon. A constant rate of interception and expulsion by atoms can cause the average speed of the light to be slowed, but the photon is always moving at c. The crystal/laser combination mentioned in the article just keeps the energy from the light a LOT longer than the picoseconds it spends in electrons normally
      • What I'm really curious about is: Where does the photon go when it transfers it's energy to an electron? Isn't a photon energy? Or is it matter? Or does it turn from matter into energy and back again?

        I know it's a strange question, but I'm not trolling, I'm just genuinely curious.

      • Only average lightspeed changes. The speed of light (photons - same speed as all massless particles) is always c (about 300kk in m/s). However, the light can be delayed. When a photon hits an atom, it usually transfers its energy to an electron, which jumps to a higher orbital.


        I think that there may be a problem with this idea. I vaguely remember from E&M (that's electricity and magnetism, for you non-EE's) class that the speed of light in a medium depends upon its dielectric constant. Vacuum had the ``fastest'' dielectric constant, thus c is the upper limit. It was the change of speed which caused the refraction when light moves from one medium to another.


        I'm quite sure that I remember from antennas lab that the speed with which electric, magnetic and electro-magnetic waves propagated depended upon the sort of coax or wave guide you were running them in. There couldn't be any question of photon absorption there, could there?


        Another post also says that the re-emitted photon has random direction, which seems an insurmountable difficulty.

      • As you might know from basic physics or chemistry, atoms can only absorb photons of specific wavelengths. In most solids there is sufficient flexibility that it can absorb a significant range of energies, but this still doesn't give the answer.

        Light can be thought of as the propagation of transverse electric and magnetic fields (centered on the photon). As they move through a material the travelling fields cause electrons (and atoms) to vibrate in response for a short period of time. However, the material has an inertia and the acceleration of charged particles generates a counter impulse of electric and magnetic fields. The response has exactly the right characteristics to impede the motion of the light's field, but typically at much lesser amplitude. The difference in magnitude of the response explains why light is typically slowed and not stopped.

        Oh, and in the case in question, they are presumably converting the energy of the photon into a vibrational excitation within the material rather than an excited electronic configuration.

  • The Previously Mentioned Method (Score:3, Informative)

    by TRoLLaXoR ( 181585 ) <trollaxor@trollaxor.com> on Tuesday January 08, 2002 @05:11PM (#2805909) Homepage
    Fucntioned by super cooling a special gas in a chamber, and then shining a specialized laser (yeah, I don't know the specifics) through the gas, opening a pathway through it.

    Light was then shined through this pathway, then the laser was cut, "trapping" the light in the gas. What actually happened was that this left an "imprint" in the cooled gas, and when the laser was beamed through the gas again, the imprint of light activated and the beam of light continued.

    There was a serious issue with degradation though. The longer the light was trapped in the gas, the poorer the quality the beam of light was when it was reanimated.

    Seems like this new method has improved immensely upon that weakness.
    • Actually, they don't say anything about the degradation in the article. Since the light is trapped/distributed among the atoms in the crystal, my guess is that degradation time will be increased, as the extra energy trapped in the atoms has to escape through a rigid matrix, vs. a gaseous flexible matrix as was previously mentioned.

      What I can't figure out is what they're really doing. Without the 2nd laser, the effect doesn't occur. Therefore, are they doing some sort of destructive interference, rather than "storing" light? Or, are they using the 2nd laser to tune the yttrium silicate+Nd atoms to "accept" extra light energy without releasing it? Normally you put that much extra energy into an atom, and it will try to release that energy to get back to ground state. The energy can be released as heat, light, or kinetic energy. I wonder how hot the crystal gets while its holding the light? Also, they don't say what the quantum yield is of the light after release. I'm guessing it must be high, otherwise they wouldn't be promoting this.
      • The second laser performs as an energy pump. A photon of the correct configuration could raise an electron to a new energy state. A second laser, emitting photons of another configuration, could raise the new energy state to a higher level. It might be the means used to keep the electron from falling immediately to the base energy level. If all of this sounds like the process is somewhat more complex than the simple description in the article, that is correct. If the developers have succeeded in stopping, then restarting light after a measurable time delay, even a very short one, they have made progress. Getting atoms and electrons to stabilize in desired states at room temperature is not a simple lab exercise, and achieving it is a major accomplishment.
      • Disclaimer: IANAQP (I Am Not A Quantum Physicist)

        My impression from the Scientific American article a couple months back was that the 2nd laser allowed the ultracold sodium gas atoms to convert the photon to a wobble in the spin rather than raising electrons to higher energy levels. This spin wobble then traveled as a wave through the gas. When the second laser was shut off, the spin no longer traveled, and was kept in place. After the second laser was turned back on, the wave traveled again. Only once the wave exited the gas, was it reconverted to a photon.

        However, I don't know whether or not they are using a similiar method for the solid crystal, or whether I got the wrong impression at all from the first article. As I said, I am not a quantum physicist.

  • The Crystal of Earendil? (Score:5, Funny)

    by Colin Winters ( 24529 ) on Tuesday January 08, 2002 @05:17PM (#2805991)
    Is this basically what the crystal Galadriel gives to Frodo does? Stores light, until it's needed in his "darkest hour?" If it is, it means that those damn elves are still decades ahead of us in technology! We must find them, take their tech, and destroy them!

    Colin Winters
    ...who thinks Galadriel is hot...

    • War with the Elves? Suicide! (Score:5, Funny)

      by ColGraff ( 454761 ) <maron1 AT mindspring DOT com> on Tuesday January 08, 2002 @05:54PM (#2806304) Homepage Journal
      Vietnam aside, I really don't like the chances of any army against one with significantly superior technology - and the US army is heavily trained to rely on the superiority of its tech.

      Futhermore, the peaceniks would have a field day with this - I doubt the Elf War would be very popular on the home front. It would take a really strong president to overcome this...

      Vote Sauron in 2004!
      (This post was a paid message from the Committe to Elect Sauron, a not-for-profit organization dedicated to America's future as the stronghold of the Dark Lord.)
    • Once upon a time Feanor (employee) created the Silmarils, and they were pretty nice. The gods (management) took notice of Feanor's creation and said, "Hey Feanor, we've got a project for which the Silmarils would come in really handy, so would you kindly hand them over". Feanor then said, "Fuck you, I made these on my own time and if you want them then make some up for yourselves!" The gods then replied, "Were sorry,
      but were afraid that were going to have to let you go for your attitude unless you come off of the Silmarils." Feanor replied, "Fine, then let me go." The gods then said, "We'll also make sure that you never work in this town again." Feanor laughed, " Good I don't want to work here anyways." The gods then left Feanor with a final admoninition, " Oh yeah, well see about that! Who will pay you more than we did for the kind of work you do here? You'll really miss the paycheck if nothing else about this job." Feanor was silent; yes he would miss the paycheck, but the Silmarils were worth it!

  • The reason it's old news (Score:5, Funny)

    by ch-chuck ( 9622 ) on Tuesday January 08, 2002 @05:19PM (#2806003) Homepage
    is that they've not only stopped light, but made it go backwards, reversing time, so this 'discovery' got projected into the future, where we're reading about it now as if it were new, altho it's been done some time ago.

  • Bob Shaw (Score:2, Informative)

    by nagora ( 177841 )
    Other Days, Other Eyes [compuserve.com] (half way down). Out of print at the moment but worth getting.

    TWW

  • At long last, no more Dark Crystal (Score:3, Funny)

    by kryzx ( 178628 ) on Tuesday January 08, 2002 @05:20PM (#2806020) Homepage Journal
    At last, we can get some light into that thing. I was getting really tired of The Dark Crystal [imdb.com]
    :-)

  • Is it just me... (Score:5, Funny)

    by TheFrood ( 163934 ) on Tuesday January 08, 2002 @05:20PM (#2806026) Homepage Journal
    ...or does the picture at the start of the article make everyone else think of "Missile Command"?

    TheFrood

  • This page . . . (Score:5, Informative)

    by OverlordQ ( 264228 ) on Tuesday January 08, 2002 @05:23PM (#2806054) Journal

    helps to explain [aip.org] how they're achieving this with a graphic representation. Still a little technical for me, but it kinda makes sense.

  • Needs a better name... (Score:3, Funny)

    by macemoneta ( 154740 ) on Tuesday January 08, 2002 @05:24PM (#2806060) Homepage
    "a crystal of yttrium silicate containing a few atoms of the element praseodymium"

    They need a catchy marketing name... Something like DyLithium Crystals.
  • To quote Groundskeeper Willy: "I a-doon't git it."

    They 'shackle' the light pulse to an atom so that it can be released later, and all it's "energy is transferred to the electron."?

    I thought that could only be done by: causing an electron to jump to a higher orbital (thus higher energy), or adding another electron through ionization.

    So can they boost an atom to a higher orbital without filling the lower orbitals? Like bumping an S-1 up to a P-2 or something? Maybe you compare what the energy level is as opposed to what it should be (e.g. three orbitals above normal) and that represents the data (plus spin, too?)

    Gee, it's fun to speculate when ZERO DETAILS are given in the article.
    • I agree. The experiment looks neat, but I need more details. If they put the light energy into the atoms and jump it up to an excited state, how do they keep it there and prevent it from coming back down to ground state and letting the light go? My guess is that the Neodynamium (Nd) atoms have something to do with it. Perhaps they can handle the light energy and stay in an excited state for longer. Or, perhaps the energy is converted electrons in the outer shells of the Nd atoms, thus changing their oxidation state in the crystal. Its not unheard of for light to change oxidation states in crystals so this could be the route/mechanism which allows this to occur.

      I agree most of all with the speculation bit. I do not see how this will open up quantum computing. Unless they can show that the stored light energy causes energy states of the atoms to entangle and become coherent, thus doing calculations based on the coherence or lack of coherence of the energy states/orbitals, I fail to see how this sort of energy storage is the breakthrough on the way to quantum computing.

  • Power Industry? (Score:3, Interesting)

    by skroz ( 7870 ) on Tuesday January 08, 2002 @05:39PM (#2806192) Homepage
    Could this be used to create more efficient solar panels? The photons are converted directly into energy, "stored" in the atoms. Rather than re-release the photons as light, would it be possible to capture that energy and convert it into something more useful?

    My understanding of optics is rather lacking... something is nagging at the back of my mind telling me that this wouldn't work...

    • I actually don't think so. It looks like this process requires a coupling laser. If you change that laser, you can retrieve the earlier packets of light. So unless you're willing to shoot a laser at your solar panel, this method really wouldn't work. There's also all that extra energy you need because of the coupling laser. With this particular process, you probably wouldn't see any increase in efficiency. You're better off with better materials for your solar panels.

  • Anything that brings us closer to proving Dark Sucker Theory [netcom.com] is okay in my book.
    • That link is just downright hallarious and well with the innovations of virus programmers I can believe that this is completely relevant.

      What ever happened to the old idea of "Computer programmers can make viruses, but choose not to". We need to quit making these people celbrities and start going back to the old hacker code of ethics.

      So read the link and mod the parent up.

      Signed AC because it's more fun ...

  • The light is converted to another representation than light inside the crystal, so technically, the light is not being halted. Rather, it is being converted to another form, and then later converted back to light again.

    Specifically, "stopping light" has nothing to do with it, though that is what the media in my country keeps calling it.
  • Wasn't there a series of science fictions stories about "Slow Glass" - glass which can hold light for years before emitting it? I love when nature imitates art.
    • I was going to post this as well, AFAIK it was a short story in which the main character went to somebody who manifactured these.

      These 'slow glasses' were put close to beautiful spots and left there to soak up the imagery, then you could buy them and put them in your living room and see what they saw for a few years (wouldn't it be way cool to have a huge 'picture window' of a waterfall that freezes in winter etc.)

      IIRC the story ended with the character noticing that the artisan had some glasses of his family when his wife was still alive.

      Does anybody remember the title/author of this story?
    • Qengho mentioned Bob Shaw's "The Light of Other Days" I'm not sure if this was the same as "Other Days, Other Eyes". I believe he has used the concept in at least one other short story, as have other authors.

      There was also the short story (probably published in F&SF magazine?) where the local bordello went out of business, and everybody bid up the mirrors to amazing prices after hearing a rumor of 'slow glass' type image extraction from antique mirrors...

  • Currently, if you want to do network testing in the lab, you have two options for emulating the delay [internet2.edu] of a real WAN:
    • An electronic delay generator that simply buffers packets;
    • Fiber loops.
    Fiber loops are better (they introduce no jitter [internet2.edu]), but more expensive and cumbersome. Maybe in a few years you'll be able to get a short strip of fiber that'll generate tens of milliseconds of delay.

    I wonder whether there's any signal degradation in the light that passes through the crystal.

  • Holographic Buffer (Score:5, Informative)

    by Vortran ( 253538 ) <aol_is_satan@hotmail.com> on Tuesday January 08, 2002 @05:57PM (#2806321) Homepage
    You guys don't get this, do you? It is not a "light capacitor" or a new twist on "glowies". What has been done here is to use subatomic particles to store information about coherent light signals.

    Perhaps some of the enlightened /. geeks remember stirrings that show up from time to time in cyberspace regarding holographic 3D memory. The premise is that, using holographic media, it is theoretically possible to store massive (a terabye in 10 sq. cm) amounts of data in an extraordinarily small space without electron lag which is a problem in high-speed microelectronics.

    In optoelectronic computing systems and quantum computing systems the ability to store photons and photon signals is tantamount to the realization of full scale optoectronic (and quantum-based) computing.

    I digress. This is awesome and I am very enthusiastic. Once again, it doesn't stop light, bend time, slow light, warp space or anything else like it. And it doesn't glow in the dark. It's like a single-channel holographic buffer and it is absolutely wonderful!

    Vortan out
    • What has been done here is to use subatomic particles to store information about coherent light signals.

      "Coherent light... you mean it can talk." - Mr. Taylor Real Genium

  • I'd be really curious to know if the medium was at all heavier, once it was holding trapped light.

    I'm guessing if it were heavier, the difference would be far too small to measure?

  • If we can stop the emission of light and trap the little photons, then what is to say we can't determine their spin, hence have a good look at everyones wonderful quantum encrypted messages. Stuff a crystal of this in the fiber and start to monitor the structure of the data packets, pick out your favourite light encrypted message, pass on, then look at the trail it made.

    I'm old, my brain is addled, but being able to stop light, or its immediate emission, has to have counter intelligence uses.

  • Amazing New Material (Score:5, Funny)

    by istartedi ( 132515 ) on Tuesday January 08, 2002 @06:20PM (#2806472) Journal

    Amazing New Material! Stores Light!!!

    Buy our amazing new Oak Light Trees (TM) today. So attractive, so easy to use. Just follow these simple instructions:

    1. Put Oak Light Trees (TM) in ground.

    2. In most climates, do nothing for 5-100 years or more depending on how much light you need and when. In some climates, you may need to water the ground in the viscinity of the Oak Light Tree (TM).

    3. Cut the base of the Oak Light Tree (TM) with a chain saw or axe, or simply have someone knock it over with a bulldozer, then cut into smaller pieces.

    4. Allow to dry for 1 year.

    5. Light the smaller units of the Oak Light Tree (TM) with a match or lighter until they begin to emit light on their own. Add larger and larger pieces until the light is satisfying.

    Amazing!!! And not only do they provide light, but heat as well. Buy today. Only $20/piece.

  • Gee, I didn't know that MS already has Windows XP installed onto a crystal. That's the only explanation. XP is the only thing that suck that hard.

  • So could I create a laser, fire it into this crystal, then release it later?
    Thus putting the massive equipment it takes to generate that laser energy in one place, charging a crystal, put it into my blaster clip, then fire it later?

    Can I store light, then later release it into a solar collector or cell? if so this has great potential to be "the perfect" battery.

    As I sit here typing, I have about100 other ways this could be used. Time to fire up the ol' patent lawyer!
  • Were this experiment conducted in conjunction with one measuring the quantum entaglement of those particles in the medium used to "store" the light, I wonder what effect it would have on the spin of the particles on the other end?

    A little simpler: a) Quantum entangle the Rb particles (or some of them) with those at a distance. Observe spin.

    b) perform this experiment (the one used to "store" light).

    c) Observe the spin of the remote particles.

    Any change? This would further explain the effects of Quantum Entanglement because not only would the spin of those particles not included in the experiment theoretically change, but one would know it wasn't a change caused by observation alone.
    • Now, if you were able to induce change using quantum entanglement with stopped light in these crystals, couldn't you theoretically make an instantaneous communications system that transmits data via encoding using the changes in spin? (and has no connection as we know it between them, wired or RF)
  • How long can they keep the light stopped without too much degradation of the signal?
  • if it is stored in the crystal, and I walk past the crystal, it is no longer traveling a c in respect to my perspective, so wht does this do to relativity?
    Will the proton decay?
    If light is an effect of another dimension, does the other dimension feel any effect when we stop light?
  • e=mc2
    c is now 0 for this light particle

    e=m02
    e=m0
    e=0

    if there is no e, then how do they expect it to "represent" a bit of information?
    • Binary is either a 0 or a 1 - an "on" or an "off"

      Pretty much, light is the switch for this bit, instead of an electrical pulse.

      Where the paticle is trapping light, it exists in a "0" state according to your equation. (I'd say that while it traps light it exists as a 1 state, simply because it's obviously holding something, but we'll go from your equations.)

      Therefore, where C' = C, the actual speed of light, your crystal would have a "1" state, where it had energy.

      Binary represntations right there - just what computers use now.

      I'd switch the definitions if I were you, but logic gates could be constructed either way I'm sure.
    • c is the constant of the (maximum?) speed of light in a vacuum, not the actual speed of light.

      don't worry, your universe isn't going to explode.

      not yet.

  • Is it possible? Can you calculate and model such a thing?
  • thinking what I'm thinking? LIGHTSABERS!!!!

    A light pulse that is brought to a standstill is not destroyed. The atoms 'remember' it, so the pulse can be regenerated by changing the intensity of the coupling laser to allow the atoms to re-emit photons - the particles of which light is composed.

    This sounds like it came straight out of the a Star Wars technical manual! Maybe when Star Wars Ep III comes out, Lucas will be able make his billions by packaging a tiny lightsaber in every happy meal.

  • First they speed [msnbc.com] it up now this!

    Actually, I noticed someone earlier [above] saying that the light somewhat went 'back in time'.

    This is nothing new as it's be a theory for years that particles move back in time for a moment.

    Read more here [stanford.edu] if you want more info.

    It's actually a mind bender, but I haven't read the page above. Another source would be a book called "In Search of Schrodinger's Cat?" [google.com]. A review here. [cix.co.uk]


    Other than the Discovery channel crap I studied no Q. Physics. That book was an easy read for anyone who's taken algebra, and I finished it in less than a month. [not bad, I read it when I took a shit... you know]

  • Quantum computing? (Score:3, Interesting)

    by 2nd Post! ( 213333 ) <gundbear.pacbell@net> on Tuesday January 08, 2002 @07:36PM (#2806901) Homepage
    I actually don't see how this can be applied to quantum computing, yet.

    This sounds almost exactly like an optical transistor, except that a transistor actually is an amplifier.

    To make it more like a transistor, imagine a 2 part crystal; part A is continually primed to be discharged, laser like. Part B is the light capturing component. A 'gate' laser turns B on and off, an input laser is the signal, and the lazed output is the output.

    Quantum computing and quantum mechanics deals with superposition and tunneling, to my understanding, so unless they can feed in 4 inputs, freeze the crystal, and then get one 'correct' output when they unfreeze it, I fail to see how this is quantum.

    Given that I described a transistor, I can see this as being critical to an optical computer :)

    Source = input
    Gate = freezing laser
    Drain = output

    You can make an optical and gate this way:

    Combine input A and B into one beam. If they are in phase (both true) their output signal amplitude doubles. If they are out of phase (one true, one false) their output amplitude is zero. Pass this combined signal through two crystals.

    Pass a *second* 'clock' signal as well that happens to be out of phase and half the amplitude of a true signal. The first crystal fires true when the clock and input signal cancel to produce a '1'. The second crystal fires false when the clock and the input signal combine to produce a '-1'
    • I think this is useful for memory storage, not processing power. If you're going to build an optical computer. you're going to need to have optical memory as well (or take a giant speed hit while accessing electronic memory).

  • cloaking device? (Score:2, Funny)

    by Anonymous Coward
    so if these crystals stopp light, coudl i cover my car with these and make a clocking device?

  • MPAA ban light research. (Score:3, Funny)

    by t_allardyce ( 48447 ) on Tuesday January 08, 2002 @08:48PM (#2807218) Journal
    The MPAA announced today that it has worked with the US government to ban light research under the Digital Millenium Copyright Act. A spokes person said "We are happy that we have nipped this little thing in the bud. Controlling light would allow people to create special viewing devices that could delay light at one end and allow people to watch previously 'recorded' films. We think that such a device could even be incorporated into a pair of glasses." They then went on to speculate that quantum computers could be built that were so fast, they could generate DVD decryption keys in fractions of a second, and that there were many other uses that pirates could come up with.
  • I once read a sci-fi story about some stuff called 'slow glass' which did something like this... it slowed down the light so the photons took about 6 months to get through the glass. The upshot was that you could have a window which looked out onto a midsummer garden in the middle of winter. I never thought they'd actually work out how to do it, though.

    Heck, even if they could make it delay only a few seconds it'd make a cool effect!
  • Hmm.. this is interesting...

    Some of you may remember that uncrackable quantum encryption [slashdot.org] can be created by using a pair of photons. The problem is that the transmitter and receiver would have to be line of sight, or possibly over fiber. I wonder if two of these crystals can be used to trap the photons individually for later analysis.. Don't know if the process of entrapment within the crystal will destroy the quantum effect that makes this sort of crptography possible, IANAQP....

    -fc

  • Just a thought... (Score:2, Interesting)

    by Viceice ( 462967 )
    I'm nowhere near qualified to ponder this, but...

    If they could store light in a medium, in this case the yttrium silicate crystal, then one other property of light being that it is infinitely compressable, does that mean that we can use that same crystal as a battery that we could charge an infinite amount of energy into? Think laptop battary with the life of 1 year. (Or if the crystal becomes unstable at one point because of the amount of energy in it, make a bomb that releses pure energy and leaves no trace of itself?)
  • The last science headline that had any science beyond the headline was around the time Neal Armstrong stepped onto a soundstage in the Nevada desert.
  • If they've actually stopped the light, then the velocity is 0, therefore wouldn't the uncertainy in position be infinite (delta p)*(delta x) > (h-bar), so if that were true, how would you get the light to come back out the same crystal?

    I'm not a physicist or anything I just have a high school physics backgrounds, and I'm just wondering.
  • I mentioned this technology in the summer. I've been expecting it to be 'discovered' by the private sector for about a year now.

    It's old. 'Crystal Matrix' technology has been used successfully in real military data and power applications for at least a decade. -That's 'real military' as opposed to the highschool production version of it currently unfolding in the Middle East.

    From my perspective, I see one aspect of it working like this:

    Get everybody addicted to data technology. --Almost done. Note the introduction of the Euro, ("Citizens: To avoid confusion, try to only use credit and debit cards. Thank you. -Yours truly, The New Europe.") and the ever-growing specter of bio-metrics. (Down at my local business supplies warehouse outlet, you can already buy thumb print readers designed to lock all but 'favored users' out of computers or whatever.)

    For those of you who don't see why this is bad, consider how much fun it would be to have yourself locked out of the economy for having dissident political views. --Or for failing to pay a traffic ticket. You only get to buy bread if you heartily agree that Arabs are evil. Mm. Fun!

    After we spend the next few years allowing this paradigm to settle into place, new computer systems will be introduced which EVERYBODY must upgrade to, and which industry/government will be able to design from the ground up with the objective of making it impossible to flip on your computer without the goons being able to look over your shoulder. -That 'Encrypting Hard Drives' thing from last year? A dry run in order to learn the proper P.R. population handling techniques. They won't screw it up twice, and it's the second time that will count.

    Whatever. It's just an elaborate show. Nothing to be scared of. Sit back and enjoy.

    As such, being a lover of geek toys, my favorite part about Crystal Matrix technology is its ability to store industrial strength power in very small batteries. --Military vehicles powered by batteries the size of cigarette packs. Neat stuff. Old, but neat.


    -Fantastic Lad --"He's just making it up, right guys? He's just crazy, right? Guys. . ?"

  • Of course we've been using materials that simply *store* and *re-emit* light for a long time (phosphor anybody? glow in the dark?). But I think the real break through here is that these crystals not only store the amplitude of the light, they actually "store" the whole function, so that the same pulses over time can be retrieved. Would this imply a larger crystal could be used for permanent data storage? I can imagine sending one of these things out into space instead of a chiseled plate. It would seem a lot more intuitive than sending, say, a DVD or hard drive ;p

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