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?
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.
So it truly is vaporware!
And the people shall be oppressed, every one by another, and every one by his neighbour Isaiah 3:5
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?
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
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."
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?