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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.
And here's the story from when it was news, last year.
0xB
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
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.
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?