Slashdot Mirror
Stopping Light
Jon Abbott writes "NASA is reporting that physicists at Harvard University have managed to stop light altogether. The implications of this discovery are rather staggering -- quantum encryption and quantum computers might be just around the corner! " Well, I don't think this will mean any immediate changes - but it is a significant step.
The implications of this discovery are rather staggering - quantum encryption and quantum computers might be just around the corner!
Yeah...very, very, very slow quantum computers.
;)
-Waldo Jaquith
But what happens when light stops? It just doesn't sit there patiently for the next command, does it? I'm not a physics guy, but if light is energy, you just can't stop energy.
Colour me confused.
Karma: Excellent Birds (mostly as a result of listening to Laurie Anderson)
And here's the story from when it was news, last year.
0xB
There was an old sci-fi story about "slow glass" where people would let these light-storing windows in interesting places and then sell them.
This really sounds like a cool way of storing holographic data (which means storing a LOT of information in a small space)
this story was stopped, held, and reemitted...
-m
You catch enchiladas by picking them up behind the head and holding them underwater until they don't kick anymore -VeGas
wow... so they finally found the light switch... -Cyko
This message was brought to you by the death of 30 brain cells.
Ok this is just a point of fact: they did not stop light! They stored the information contained initially in a light wave in a new medium that they had control over, then were able to stimulate the medium to get it to re-emit.
It was not destroyed or absorbed, but rather stored -- ready to emerge intact at the scientists' bidding.
I can just see physicists getting calling people into the lab, turning out the lights and commanding, "Let There Be LIGHT!!!" at every available opportunity
--
"Outlook not so good." That magic 8-ball knows everything! I'll ask about Exchange Server next.
They tend to call them "Red Lights" though. I wanna transporter, now.
What, me worry?
Wasn't this story just on /. a few weeks ago?
I watched C-beams glitter in the dark near the Tannhauser gate.
it lends a whole new meaning to breaking something by "letting the smoke out".
:-)
Light isnt actually stopped it is absorbed by the atoms in the medium.
So those atoms go on a higher energy state, as a result of the light they have absorbed.
When they shine another laser on the medium the atoms emit the energy they had previously absorbed, in the form of the same kind of light that came in.
Stop light? This is nothing new. We have stop lights at every major intersection.
There weren't a girl and a gold watch involved, were there?
I watched C-beams glitter in the dark near the Tannhauser gate.
They stopped light last year. Theres even a guy whos trying to rewind light.
This is just old news, The way light was stopped before was they used extreme cold to slow light down until it stopped.
If you use Linux, please help development of Autopac
So it truly is vaporware!
And the people shall be oppressed, every one by another, and every one by his neighbour Isaiah 3:5
could this be used for really high density portable storage?
Would shaking the storage container make atoms discharge and ruin the whole thing?
What's worse is that he removed the end of my story submission to make room for the quip. FWIW, this is how the original story submission went:
Jon Abbott writes "NASA is reporting that physicists at Harvard University have managed to stop light altogether . The implications of this discovery are rather staggering -- quantum encryption and quantum computers might be just around the corner! <coffee-talk>Discuss.</coffee-talk>"
Slashdot's first reaction to VMware
Do you have any idea how many atoms you can fit in something the size of a CD? That's a lot of data to store MP3's on!
"Derp de derp."
I just don't believe they stopped the light.
is not that it's a year old Slashdot repeat; we're used to that. The problem is that the whole "stopping light" headline that all the mainstream journalists (who should know better) carry on it is baloney.
If a photon (light) hits an atom (matter), causing it's electrons to move to a more excited energy level, I defy you to "show me the light". You can't. You can show me a really excited electron, and if you're really clever like these folks at Harvard you can even get that atom to release the exact same light with the exact same waveform, but you haven't stopped light.
It's annoying. How hard is it to say you've "trapped" light?
He means that it won't mean any significant changes in how we build computers--that is, quantum comptuers are still a ways away. But it is a VERY significant step. If you read the article, they explain how they stopped a laser beam and turned it into information, stored in the up-and-down patterns of the vapor's atom's spin axes.
I mean, you don't have to be a scientist to imagine the possibilities of a vaporous hard drive, with a huge capacity, that gets written to by a laser that changes the state of the atoms within. Drool...
And the best part is no more annoying spinning noise!
c-hack.com |
There are a handful new (or at least vastly improved) technologies that will be developed and put into use in the near future that will rival the changes ushered in by the developement of the microchip. This could happen much sooner than most people think, maybe as soon as 4 or 5 years. Quantum computing will be one. It will be crude and a lot of people will look upon it the same the that the Altair or the GUI developed by Werox PARC, but advances will happen fast once things get moving. Nanotechnology will be another. Tiny machines that can clean out clogged arteries will be "neat" but this will really be useful in materials developement. Once we can custom build materials at the atomic level, things will get interesting in a hurry. Being able to stop light is something that sounds pretty obscure, but then so was a little hunk of silicon Bell Labs touted 50 some years ago. I've talked to some people who were working in the electronics industry when the transistor was first talked about. A lot of them at the time thought "Well, that's neat, but that thing will never be able to handle any serious current. Intel made a real gamble in the 70's with their little "calculator-on-a-chip", the microprocessor, that they made in the hopes of selling it to a Japanese calculator manufacturer. It will be interesting to see what comes down the road from what these people did with stopping light.
I've noticed a couple of people wondering why this discovery important. Some other people know that it is useful for quantum computing, but they don't know how it would be useful. I'll see if I can help.
The most common way qubits are stored in quantum computers is as spin, which can be thought of as angular momentum, quantum-style. The particle usually used for this task is the electron. So, now we've got the qubit stored as spin, but how do we get the different particle's spin states to interact? If we can't get them to interact, we can't do any computation, so this is a very important question.
The most successful quantum computers (those with 7 qubits) so far use Nuclear Magnetic Resonance (NMR) to make the qubits interact. This has it's problems, and would not be appropriate for a real quantum computer. So, to make a real (ie. Desktop) QC, we need something better.
This story talks about a method of turning information stored in light (as amplitude, IIRC) into spin. This sort of translation is exactly what is needed to make quantum computers work. An example QC could use a bunch of atom's as the memory system, with all of the qubits encoded as spin on the electrons orbiting the atoms. The CPU would be a bunch of optical components (beam splitters, polarizers, mirrors, etc.) that operate kind of like transistors. And the wires would just be fiber optics. Now, this is a little simplified, because it assumes we can make atomic scale optical components, but I am confident that it will happen soon.
Hope this helps some people understand why this is Stuff that matters.
Yes, I'm still a junky. Are you still a bitch?
We've known that light can slow down since 1850. The speed of light does change when traveling through various things, depending on its index of refraction. So, you are not correct -- light can be and is slowed down easily.
This is the four thousandth time this article has been posted here and it is still doesn't follow. Nobody is freezing photons, they're just getting them stuck in the middle of some molecules so they have to wait for another laser to be able to knock the photons loose again. Stopping photons is not the same as trapping them.
I'm a loner Dottie, a Rebel.
my @quanta;
@quanta=;
foreach $quanta (@quantum)
{
warn "DAMN! destroyed my data by reading it again!\n";
}
-- Two men say they're Jesus. One of them must be wrong. - Dire Straits
Slashdot and articles in general on the net are so misleading when it comes to anything related to physics. Where do you people come from? Leave the physics to physicist. Anyway, they didn't "stop" light. This is nothing more than a simple setup (in theory) that's based on what any grad physics student must do (time dependant pertubation theory). The light perturbs the spin 1/2 states of the Rb with off diagonal matrix elements that mix states. The polarization of the light with respect to the Rb is also very important. The physics going on here is what you could call Rabi flops. It's a simple time dependant pertubation theory problem that is exactly solvable and can be reduced to two by two subspaces. As far as the physics goes, they've done nothing all that new or exciting. The only advances they've made are perhaps technical advances in setting things up.
Slashdot is so silly sometimes it makes my head hurt.
Headline: Physicists Stop Light
Slashdot: The implications for quantum computing are staggering!
Headline: Transparent Aluminum Invented
Slashdot: The implications for case mods are staggering!
Headline: Secret of Time Travel Discovered
Slashdot: Yay! We don't have to wait 2 years to see the rest of [insert name of trilogy]!
Headline: Scientists Cure Cancer
Slashdot: The implications for quantum computing are staggering!
Headline: Terrorists Nuke South Dakota
Slashdot: The implications for quantum computing are staggering!
but this phase information is quickly lost as the atoms move around in a thermal equilibrium. think about it as sky-writing. the information is written there, but as the particles move around the infomatino is quickly lost.
most of these experiments have been done with UltraCold atom clouds, and the most recent ones (presented at DAMOP last year) were done in Bose-Einstein Condensates.
due to the very short "coherence time", this phenomena is most likely not very useful for quantum computing.
the buzzwords to look for when it comes to quantum computers (i.e. the things most likely to work) are "trapped ions" and "optical lattices". i promise, one of those two will be used in the first functional quantum computer.
muerte
Actually, the biggest problem is the conversion of sunlight to a more useful form of energy. Photovoltaics suck big time in the cost and efficiency departments. Places with no shortage of sunlight (like Arizona) can't use solar power for even a modest fraction of their power generation needs.
Is this really news, or hasn't this been done...
before?
or before?
-D
Damn, it seems we're getting close to the Improbability Drive.
"That's a good name --- ground! I wonder if it will be friends with me?" Thud!
Miko O'Sullivan
This was published in Nature over a year ago (25 January 2001 to be precise). This article (PDF format) is a nonspecialist introduction to this work, and this article (PDF format) is the peer-reviewed research article from Nature.
"It take 9 months to bear a child, no matter how many women you assign to the job."
The Smith family (complete with mom, dad and 2 children) is taking a 4-hour trip to Grandma's... Kid 1: Mom, are we there yet? Mom: No (Repeat 15x) Kid 2: How long's it going to be? Dad: Ok kids, if you don't keep quiet back there I'll split you up into an uncountable number of atomic particles and stow you away in your Ronald McDonald sippy cup until we get there! Kid 1: ...
Kid 2: ...
... not many Slashdotters killed.
[cf. Small Earthquake in Peru for the humor impaired moderators]
--
E_NOSIG
You might be surprised how many Slashdotters are in South Dakota.
We're going down, in a spiral to the ground
Assume you make an incredibly good mirror: it's 99.999999% reflective. (How you're going to manage to do this while still pumping light in from the outside is unclear- 1/2 silvered mirrors are exactly that.) No mirror is even close to this value, BTW- the best around can do about 99.99% or so.
Assume you have a 1 m diameter ball. Light travels 300,000 km/sec: 3e8 m/s. Thus, you get 3e8 collisions with the mirror every second. Total saved light= 0.99999999^3e8 ~= 0.05. In other words, after 1 second only 5% of the light remains.
"Photon torpedoes" supposedly use matter-antimatter as a power source: pure mass-> energy conversion- why bother with light at all?
Eric
"Seven Deadly Sins? I thought it was a to-do list!"
I know you were joking, but you really can do Quantum computing with Perl
-- Will quantum computers run imaginary-time operating systems?
i hate to be a dick, but i have to agree with this guy. kind of reminds me of the reaction to the "jump to conclusions" mat in Office Space.
...is how they release it? Anyone has clues?
They can absorb light into a container, alter the qubits (how?), and then, how do they send it off again? Opening a quvalve?
Some quEstions require quAnswers.
These bozos need to document a bit more if I'm to build one myself (ok... maybe I'm optimistic).
In other news, the RIAA filed suit today against God for failing to include Digital Rights Management technology with each atom, in violation of the SSSCA, and for providing an anti-circumvention mechanism within His "Laws of Physics" prodict.
"This will destroy the music industry as we know it!" exclaimed an unnamed music industry representative, "Evil Hackers will be able to use this technology to pirate music off of even protected CD's, because they're all made of atoms!"
God was contacted for comment on these developments, but apparently prefers only to listen, and not reply.
The thing about things we don't know is we often don't know we don't know them.
I've been doing that for years. Ever since I learned how to use the light swtich.
someone else has just discovered how to let light in. It is not know yet if their product's name will be contested by Microsoft Corp.
The article mentions experiment from 1999 where light was slowed to the "bicycle speed". This was accomplished by shining light trough "Bose-Einstein" condensate. Bosons are particles with integer spin (e.g. photons). In 1924 it was predicted that an ensemble of bosons could, under certain conditions, undergo a phase transition. This is analogue to vapor condensation or crystallization of liquid. In order to create Bose-Einstein condensate it is necessary to achieve temperatures less than one millionth of a degree above absolute zero. First successful experiment was performed in 1995 utilizing laser cooling. One of the properties of BE condensate is that the light propagates trough it with speed that is 20-million-fold slower than a speed of light in vacuum.
h tm l,
The article is not very informative about actual physics involved in the newest experiment. However there is a nice description at: http://www.aip.org/physnews/update/521-1.html.
Also there is a an interesting site about Bose-Einstain condensation at
http://www.colorado.edu/physics/2000/bec/index.
with some nifty Java applets
The Palestinian-Israeli conflict will be resolved, global warming reversed, and world hunger ended. I am definitely staggered.
(having one of those days when these sorts of breakthroughs seem ever so slightly irrelevant to the future of life on Earth - could you tell?)
Next they reduced the intensity of the signal laser until the polariton was 100% atomic. There were no photons left inside the chamber.
There were no photons, people. They didn't stop light. Halted light would mean there are photons in there, moving at exactly zero meters per second. There were no photons left.
That that is is that that that that is not is not.
One step closer to a working light saber. Thank you Harvard!
Blearf. Blearf, I say.
AFAIK light always goes at the same speed, but it takes longer to get through certain media than others - this is because it doesn't go in a straight line (and why when someone quotes the speed of light they use the speed of light in a vacuum as a reference).
Light isn't 'stopped' in the sense that it hangs there waiting for something to happen (which doesn't make sense if my (limited) understanding of physics is even close to correct), it's simply absorbed into another particle then that particle emits light some indeterminate time later.
btw. Not all galaxies have a red shift. Andromeda has a blue shift (it's coming towards us apparently).
Am I the only one who thinks it's strange that while we get told about all these fantastic things that can be done which weren't possible a year ago, people still say convincingly that "you can't get the state from the system without leaving finger prints" ?
I'm sure we can't today. And I'm equally sure that someone is going to figure out a way to touch the system so insignificantly that the "reading" cannot be measured.
Like when reading from a hard-drive: Of course the head will alter the state of the platter when passing by - it's just so insignificant that it doesn't matter, and it would probably be hard to measure if anybody tried.
While this is fascinating and all, I just don't buy into the "can't cheat with this one". Many years ago, everyone agreed that you couldn't split an aton - which was natural, because "the atom" itself was a relatively new idea in itself at that time.
I find it hard to believe that the progress stops here.
... on New Year's Day. Millions of hungover people will thank them for stopping that godawful light ...
Doesn't matter anyway though because such equations only apply to particles with mass. Since light travels at the speed of light, it cannot have momentum or mass.
Einstein was a pretty smart guy...
int func(int a);
func((b += 3, b));
Said it better than I could...
Always curious why people post good stuff AC.
int func(int a);
func((b += 3, b));
Headline: Terrorists Nuke South Dakota
Slashdot: The implications for case mods are staggering!
-
- - You can't take something off the Internet! That's like trying to take pee out of a swimming pool.
This is really old news and not even "technology." Following the examples in California and this ENRON thing, it's clear that stopping light isn't so much a technical marvel as it is poor management.