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
And here's the story from when it was news, last year.
0xB
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
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?
The energy itself isn't really "stopped", it's transformed into a different form. When the photons of light impact an atom, it leaves an imprint (in the form of a spin). So, each unique wavelength of light leaves a unique imprint which can then be fetched at a later date by another laser pulse (or so the article says) Hope that sheds some light on the subject. :P
From what I understand this is more akin to storage and retransmission.
The energy itself I believe is lost, though the waveform of the light, and its pattern is stored in the arrangement/orientation of the atoms. Shining another light into the atoms causes the eminating light to be of the same waveform/pattern.
A better analogy would be intercepting a streaming movie going across your network, waiting a while, and then re-transmitting it. You're not sending the same electrons, but you're sending the same bits.
Stop light? This is nothing new. We have stop lights at every major intersection.
So it truly is vaporware!
And the people shall be oppressed, every one by another, and every one by his neighbour Isaiah 3:5
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 |
My read is that it's just the information about the light that's stopping: wave amplitude and frequency. This information is imprinted on a non-moving medium (spin states of the atoms) and then released later when the atoms are excited: a wave released with the same properties of the incoming wave that was absorbed.
:) ] of the story. I'm not a physics guy either and sometimes I think they try too hard to mystify and dramatize the terminology when it's moved from math to English (especially on "Isn't it a wonderful time to be alive"-NASA press releases).
I can't see what the technical reason is for saying dramatically that this information is "stored" and not "absorbed" - looks like it's just arguing about the spin [
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?
"Light of Other Days"
Bob Shaw
First came out in '66
Still gives me a lump in my throat just thinking about it.
You either believe in rational thought or you don't
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 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!
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."
... not many Slashdotters killed.
[cf. Small Earthquake in Peru for the humor impaired moderators]
--
E_NOSIG
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?
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.