Scientists Freeze Pulse Of Light 343
Smitty825 writes "After slowing down light to slow speeds, scientists at Harvard University have been able to stop light for a very brief period of time without destroying its energy. The article explains how it is different from this previous light-stopping science story - this will hopefully help the development of quantum computers and ways to communicate over long distances without being eavesdropped on."
Apparently, there is energy loss (Score:5, Informative)
"We have succeeded in holding a light pulse still without taking all the energy away from it," said Mikhail D. Lukin, a Harvard physicist.
This is somehow different from "...without destroying its energy." like it is stated in the posting. Maybe a subtle detail, but not quite the same.
However, a briliant achievement. Kuddos.
Another article (Score:5, Informative)
"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."
Well you could have found it (Score:5, Informative)
More links (Score:5, Informative)
Larkin's article itself is here [lanl.gov].
Any physics nerds want to explain it to us?
Re:More links (Score:5, Informative)
Re:If we stopped light, (Score:2, Informative)
Re:If we stopped light, (Score:2, Informative)
Greatest breakthrough ever? (Score:2, Informative)
Re:More links (Score:1, Informative)
but there's a stronger concept at work in this light thing too, indistinguishability. Sometimes, the 'same' photon doesn't mean anything. actually, it never means anything. photon is the observed quanta, and you can only ever make the observation once, same with electrons.
Re:SF story with slow-light windowpanes? (Score:5, Informative)
Re:Interesting note/errata (Score:5, Informative)
Here's a better explanation [dartmouth.edu] than I can muster.
Re:Is brief really very long time for the Photon? (Score:5, Informative)
They're not stopping the photon. They're simply storing it in several atoms quantum spin. Then they hit it again with a laser and get the earlier pulse back out of the quantum spin stored in the atoms. It's rather limited because, quoting from Science News
However your post should be modded funny, because it's a witty, clever response rather than the usual worn jokes which somehow seem to get modded up all too frequently.
Reminds me of a childrens story I read once about a time machine, which was based on a nutty inventor who managed to build a car that got progressively faster. First of all it took a minute to get a specific distance, then 30 seconds, then 1 second, until in fact it took no time at all and then less than no time to get there until it ended up travelling backwards in time...
Links to Quantum Cryptography information (Score:2, Informative)
More on this:
here [dartmouth.edu]
here [qubit.org]
and here [csa.com]
Re:Actually uncertainty applies here. (Score:4, Informative)
4 * pi * uncertainty in time * uncertainty in energy >= Planck's constant
(I believe you can use the standard deviation as the uncertainty here.) This "law" that results from our model for quantum mechanics thus tends to put a limit on how fast a quantum/optical computer can be.
A few more details (Score:3, Informative)
Say what? (Score:3, Informative)
We already have that. Light based fiber runs are impossible to tap into without having to break the connectivity to hook up an additional device. Of course, nothing goes coast-to-coast directly, so they're plenty of chances for the spooks to install their logging equipment at a switching station or router.
The only way to communicate securely without encryption is to totally control physical access to the line, which just plain isn't gonna happen over long distances.
Re:If we stopped light, (Score:5, Informative)
Re:Speed of light inconsistencies (Score:2, Informative)
But interstellar space is mostly vacuum, so n is nearly 1, thus c is mostly correct.
What they're actually doing (Score:3, Informative)
This is quite different from what's going on here. In this experiment, two lasers are used to polarize the atomic vapor as a function of position, and then bouncing light off that polarization gradient. Think of what happens when you put light in between two highly reflecting mirrors, and let it bounce back and forth. Then think about what happens if you nest thousands of these mirrors within each other, so that if the photon leaks out of one, it has to deal with the next one, only one wavelength away. Since the photon is spending so much time bouncing back and forth, it doesn't really have a chance to escape the gas, and so we say that it's trapped.
It's essentially a new way of making a high quality cavity.
Re:SF story with slow-light windowpanes? (Score:4, Informative)
Re:Color != frequency (Score:5, Informative)
He stated the 'color' of our photo receptors. Although our photo receptors pick up C, Y, and M -- it is because their colors (as he said) are R, G, and B.
ie: the Red Photoreceptor reflects RED, that is why it is a red colored photoreceptor. Since it reflects RED, it picks up BLUE and GREEN, which make one of the (secondary) colors you mentioned.
You are also wrong saying that RGB is used for pigment. Pigment gets its color by absorbing color, and you see what is reflected. RGB is used for TVs and Monitors where there is a direct source of light.
Cheers!
Re:Okay... (Score:3, Informative)
What they've really done is created a medium which slows the asorption and emittion of the photons so drastically that it is descernable by the naked eye. What they have NOT done is altered C. In other words, what they've done is the equivalent to shining a flash light through water and saying they've slowed the speed of light. This is drastically different from actually slowing the velocity of the photons through a vaccuum. In their case, their medium is constantly absorbing and re-emitting the photons. In essense, the photons that emerge from the other end are not the same photons that entered it. They are equivalent copies. Such is what happens with glass or any other transparent medium.
Finally, my area of expertise (Score:2, Informative)
First [1worldrecipes.com]
Second [lisashea.com]
third [about.com]
Re:Interesting note/errata (Score:2, Informative)
Re:Man...Imagine the vaccuum (Score:2, Informative)
Normally, we say that the color of light depends on the wavelength of the light, but technically it depends only on the frequency (not the same thing!). We know that:
frequency = speed of light / wavelength
But when light passes through any transperent material (with index of refraction n > 1), the speed of light changes, as well as the wavelength. Coincidentally, they also change by the same amount.
speed of the light = c/n
wavelength of light = L/n
where c and L are the speed and wavelength of the light in a vacuum and n is the index of refraction
Because they change by the same amount, the frequency remains unchanged. At least, this is how it works in normal transperent materials like water, air, and glass. This cutting edge stuff may be different, but the article lacks all the good technical bits for me to be able to tell.