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Scientists freeze beam of light

I

iGav

macrumors G3
Original poster
Mar 9, 2002
9,025
1
very, very impressive!

rinky dink link...

http://news.bbc.co.uk/1/hi/sci/tech/3308109.stm


or full article below.

Physicists say they have brought light to a complete halt for a fraction of a second and then sent it on its way.

Harvard University staff held a light pulse still without taking away all of its energy, the journal Nature reports.

Controlling the movement of light particles - so-called photons - to store and process data could lead to the development of quantum computers.

In a 2001 experiment, light pulses were briefly stored when particles of light were taken up by atoms in a gas.

The Harvard experiment tops that achievement by holding light and its energy at a standstill.

Light speed

Light normally travels at about 299,000 kilometres per second (186,000 miles per second), but it slows down when passing through some materials, such as glass.

The team fired a light beam called a signal pulse through a sealed glass cylinder containing a hot gas containing atoms of the element rubidium, illuminated by a strong ray of light known as a control beam.

While the pulse was travelling through the rubidium gas, the researchers switched off the control beam, creating a holographic imprint of the signal pulse on the rubidium atoms.

Earlier experimental methods had then switched on a single control beam to recreate the signal pulse, which then continued on its way.

On the pulse

However, in this latest study, researchers switched on two control beams which created an interference pattern that behaves like a stack of mirrors.

As the regenerated signal pulse tries to continue on its way through the glass cylinder, the photons bounce back and forth, but the overall signal pulse remains stationary. The light beam was essentially frozen.

The researchers were able to keep the photons trapped like this for about 10-20 microseconds.

The research was conducted by Mikhail Lukin, Michal Bajcsy and Alexander Zibrov of the department of physics at Harvard University, Cambridge, US.

Quantum Leap

Mr Bajcsy said that a distant application of controlling light would be in powerful quantum computers.

"In [quantum computers] you would have to transfer the information from photon to photon to photon. And in order to do that you have to make the photons interact with each other such that you control it very precisely," he told BBC News Online.

Professor M. Suhail Zubairy, a physicist at Texas A&M University, said the Harvard team's achievement was a significant step forward in the emerging area of quantum computing and quantum cryptography.

Quantum cryptography might provide very secure forms of electronic encryption, because the process of eavesdropping on an electronic message would introduce errors in the message, garbling it.

"This would allow you to exchange a key on a public channel, but whereas any classical system can be broken by an eavesdropper, in quantum cryptography you would always find out if someone was looking at your message," Professor Zubairy told BBC News Online.
Click to expand...
 
Impressive, very impressive! What's next, cold fusion??? Wait, hasn't that already been done...;)
 
interesting experiment, but i do wish media would be a little less sensationalizing. light didn't "stop" in the ordinary sense of that word. but public will perceive as if light is something that can be stopped if they only looked at the headline...
 
the article doesn't mention it, but i would think that the rubidium must have been supercooled to form a bose-einstein condensate
 
Originally posted by jxyama
i do wish media would be a little less sensationalizing
Click to expand...

Asking the media to stop sensationalistic reporting is kind of like asking an elephant to jump through a hoop, it just isn't going to happen. My favorite: "What you are eating for dinner tonight might kill you, tune in at 11:00"
 
Originally posted by tpjunkie
the article doesn't mention it, but i would think that the rubidium must have been supercooled to form a bose-einstein condensate
Click to expand...
One would think so, but I believe it was done in rubidium plasma.
 
Originally posted by hobbes3113
Asking the media to stop sensationalistic reporting is kind of like asking an elephant to jump through a hoop, it just isn't going to happen. My favorite: "What you are eating for dinner tonight might kill you, tune in at 11:00"
Click to expand...

i know... but it's so rare that a physical science story (not biological/medical science) grabs a headline! i wish they'd do a little better job...

(of course, you can say they wouldn't grab the headline at all unless they could be spiced up a bit...)
 
Originally posted by hobbes3113
Impressive, very impressive! What's next, cold fusion??? Wait, hasn't that already been done...;)
Click to expand...

Sure, if you didn't mind having that huge cold fusion generator being able to power little more than a few lights.
 
yeah, i saw the "hot gas" part but it just doesn't seem like a plasma would be stable enoughto cause this kind of effect without a massive loss of energy, which they said did not occur
 
Well, if it can stop the light from coming into my room in the morning, waking me up, I'm all for it.
So... we can make quantum computers by stopping light... that sounds kinda cool.
 
yeah, the light was trapped, not frozen. And if the rubidium had been super-cooled, only light of the specific frequencies that rubidium can absorb would have any effect on the temperature of the gas. in fact, lasers are what is used to supercool gases to within 1 millionth of a degree of absolute zero.
 
So basically, if I built a hollow sphere that was all mirrored on the inside with a pin hole on either ends, and stuck a lil fiber optic in on side so that the light from the fiber optic bounced around a bunch before finally getting through that little hole on the other end, I'd be pretty much doing the same thing?
 
Originally posted by jxyama
i know... but it's so rare that a physical science story (not biological/medical science) grabs a headline! i wish they'd do a little better job...

(of course, you can say they wouldn't grab the headline at all unless they could be spiced up a bit...)
Click to expand...

"Scientists employ rubidium plasma to leave imprint of photon signal pulse on atoms"

Very catchy...What's more deplorable is that researchers have to "spice up" papers for journals like Nature, as well, and not just the general media.

I must say, though, that I only extremely vaguely kind of see what's going on with this procedure. It sounds fascinating, though. Maybe the actual paper would explain it a little bit better. If someone wants to clarify what the article is trying to say, though, that would be spiffy.
 
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