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Light Stopped, Held And Re-emitted By A Crystal
Posted by
timothy
on Tue Jan 08, 2002 04:08 PM
from the dark-crystal dept.
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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Magical Crystal = Glow In The Dark Stuff? (Score:2, Redundant)
Re:Magical Crystal = Glow In The Dark Stuff? (Score:2, Informative)
Re:Magical Crystal = Glow In The Dark Stuff? (Score:2, Insightful)
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.
Re:Magical Crystal = Glow In The Dark Stuff? (Score:2)
Re:Magical Crystal = Glow In The Dark Stuff? (Score:3, Insightful)
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)
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."
Parent
Re:Magical Crystal = Glow In The Dark Stuff? (Score:4, Informative)
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.
Parent
Re:Magical Crystal = Glow In The Dark Stuff? (Score:2, Informative)
Re:Magical Crystal = Glow In The Dark Stuff? (Score:2)
OK,
- B
Re:Magical Crystal = Glow In The Dark Stuff? (Score:2)
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.
whats next (Score:3, Interesting)
constant speed of light (Score:5, Funny)
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)
Parent
The Previously Mentioned Method (Score:3, Informative)
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.
Re:The Previously Mentioned Method (Score:2)
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 Crystal of Earendil? (Score:5, Funny)
Colin Winters
...who thinks Galadriel is hot...
War with the Elves? Suicide! (Score:5, Funny)
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.)
Parent
The reason it's old news (Score:5, Funny)
Bob Shaw (Score:2, Informative)
TWW
At long last, no more Dark Crystal (Score:3, Funny)
:-)
Is it just me... (Score:5, Funny)
TheFrood
This page . . . (Score:5, Informative)
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)
They need a catchy marketing name... Something like DyLithium Crystals.
ionization? orbitals? (Score:2)
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.
Re:ionization? orbitals? (Score:2)
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)
My understanding of optics is rather lacking... something is nagging at the back of my mind telling me that this wouldn't work...
DS Theory (Score:2, Funny)
No *real* halting involved (Score:2)
Specifically, "stopping light" has nothing to do with it, though that is what the media in my country keeps calling it.
Re:No *real* halting involved (Score:2)
Hmm...slow glass anyone? (Score:2)
Re:Hmm...slow glass anyone? (Score:3, Interesting)
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?
Network delay generators (Score:2)
- 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)
Perhaps some of the enlightened
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
Re:Holographic Buffer (Score:3, Funny)
"Coherent light... you mean it can talk." - Mr. Taylor Real Genium
How did the material change? (Score:2)
I'm guessing if it were heavier, the difference would be far too small to measure?
Amazing New Material (Score:5, Funny)
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.
Quantum computing? (Score:3, Interesting)
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'
MPAA ban light research. (Score:3, Funny)
Re:It's been done. (Score:2)
Re:It's been done. (Score:3, Interesting)
Re:Which version of the Pentium (Score:3, Funny)
I bet it's the "Quantuim" :)
And the AMD response... (Score:2)
Re:Which version of the Pentium (Score:5, Funny)
Parent
Re:gee, wow..... (Score:2)
Re:gee, wow..... (Score:2)
Re:I'm lost... (Score:2)
Light goes at c (Score:5, Interesting)
A lot of people have been saying that light only goes at c in a vacuum. This isn't quite right.
Light goes always at c, period. When it goes through a solid, a better metaphor is that it has to slalom around the atoms in the solid. Of course due to QM it's really more like that Charles Addams cartoon with a ski track leading up to a tree, splitting around, and continuing on. At this point, classical approximations stop making sense, and you have to start talking about amplitudes. You can get the Feynman New Zealand videotapes here [amazon.com]. It's an excellent but basic and easily understandable introduction to quantum electrodynamics.
In any event, this doesn't seem to be the same mechanism (unless the amplitudes get stuck as if the photon were going in a loop). It appears to be a similar mechanism, as pointed out elsewhere, to glow-in-the-dark paint. Terribly exciting, but not foundation-shattering, unfortunately. It would be a lot of fun if it were.
Another minor wrinkle is that c is very slightly faster than the speed of light in a vacuum, because a vacuum isn't quite empty. Particles come into the vacuum and immediately annihilated each other all the time. You can theoretically get rid of these by putting a vacuum between two plates so close together that these virtual particles can't form.
Parent
Re:Quantum computing misses the mark... (Score:3, Insightful)
The truth is, I'm guessing here, but how else do you build a human interface to a quantum system?
Re:Is this anything like "Slow glass"? (Score:5, Funny)
When I first read a story with "slow glass" in it, I thought "That might be cool." Then I thought about how much energy was somehow stored internally if I left a sheet lying in the desert in direct sunlight for ten years. Then I thought about what would happen if all that energy were discharged at once when the crystal structure (or whatever) was damaged by, say, the neighborhood brat throwing a brick through it. And decided that I wouldn't want any of that stuff in my house!
Parent
Re:Man I need to find a physist (Score:3, Funny)
don't worry, your universe isn't going to explode.
not yet.