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Scientists Freeze Pulse Of Light
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."
Now if they could only figure out how to stop SPAM
Imagine going out to a club and getting a frozen "light cube" in your drink which releases a stream of photons as it melts.
Could bring a whole new dimesnion to the humble Tequila Sunrise huh?
A little planning goes a long way...
Oh...wait. Voids allow light to travel faster. shame on me. What color is stopped light if it retains its energy?
~mingust
One of the most annoying things about slashdot is their tendency to post completely vacuous science stories. Would it have been that hard to look up the actual paper before posting, or at least any information at all? All this story tells us is that it doesn't involve storing the photons in an atom as other researchers did. Oh, and that it's "very clever". How nice.
Does the laziness of slashdot "editors" truly know no bounds? If you're not interested in doing the work, why not find people who are?
autopr0n is like, down and stuff.
Makes me think of a physics joke.
Q: What is the difference between stopped light and darkness?
A: You know where darkness is.
I thought that light is a visual thing. How does one "eavesdrop" on light?
From excellent karma to terible karma with a single +5 funny post...
The article mentions clearly:
"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.
"I think it's moving us in the right direction," he said. "Moving forward at the speed of light"? uh oh
~mingust
If the NSA supposedly managed to tap into fiber (light) what makes this guy so sure his studies would minimize/cut/halt the risk of eavesdropping? "Splice the line, and you cut off the light, at least momentarily," says Wayne Siddall, an optical engineer at Corning Fiber in Corning, N.Y. Even a second's interruption could be noticed by a cable's operator. Cable companies typically build systems with duplicate lines that take diverging routes, in case one of them is damaged or severed. One retired NSA optical specialist insists that the NSA devised a way to splice a fiber without being detected. "Getting into fiber is delicate work, but by no means impossible," the former specialist says. Neither he nor the NSA will discuss the matter further.
Spy agency taps into undersea cable
NSA Tapping Underwater Fiber Optics
And the list goes on and on. Bear in mind the NSA's date of achieving this, in comparison to the tech growth scale, I'd be willing to say that whatever Harvard is doing in being closely watched, if not already known.
MoFscker
Sounds like you could use it similar to the initial version of electronic memory (sort of a digital delay line), if it could be harnessed.
:-)
A few hundred-thousandths of a second is an eternity(*) for a photon. That's actually pretty impressive
Simon.
(*) Yes, for the pedants amongst us, I realise it's not actually an eternity. It's a figure of speech, for chrissake!
Physicists get Hadrons!
BBC News has an article which speaks a bit more to Quantum crytography.
"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."
"Academicians are more likely to share each other's toothbrush than each other's nomenclature."
Cohen
Could "Slow Glass" be coming? Bob Shaw wrote about glass that could slow down light so that it took years to pass through and the effects it had on society in his 1972 book Other Days, Other Eyes. Anyone interested in this stuff should hunt down a copy.
Like I did here.
More detailed articles about the research can be found here or here.
Larkin's article itself is here.
Any physics nerds want to explain it to us?
This may prove to be a ray of inspiration for dim wits everywhere, beamed from the heavens to shed a new light on these dark times! Don't take it lightly. How we use this enlightenment will be a reflection on us all.
Altogether now: *grrooaaan*
Here's a quote from Terry Pratchett you might like:
"Light thinks it travels faster than anything but it is wrong. No matter how fast light travels it finds the darkness has always got there first, and is waiting for it."
Why were there no pictures of this stopped light? .. oh wait
That just means that if you were, in fact, able to drive your car through their rubidium medium, it might produce somthing akin to cherenkov radiation, another example of massive particles traveling faster than c/n.
I think you're not supposed to be able to go faster than light under the _same conditions_. If someone used forward and backward control beams to time-vary your Rabi-frequencies, I doubt you'd be going anywhere fast.
Officer: "Do you know how fast you were going?"
Heisenberg: "No, but I know exactly where I am!"
paintball
Messeges in Phillip Morris code are automatically subpoenaed by Congress anyway.
God damn, subpoenaed is an ugly word.
paintball
I once read an SF short story that featured windowpanes which light took decades to pass through - thereby letting you look at the past.
The story included the poignant scene of the protagonist looking out at his wife and child playing in the garden - but they had died 15 years earlier. The character used to hang around near the windows, hoping for glimpses of his dead wife, because he, of course, had no control over when he saw her; the windows would "replay the past" in strict linear sequence.
Does anyone know the name & author of the story?
In the story, the windowpanes were made of optical fibre nanotubes that were so tightly coiled up in the windows that the windows could accomodate tubes a few light-years long.
This research suggests more feasibly ways of doing this, though.
Light doesn't actually have "color". Color is our perception of the wavelength of the light. There's another article on BBC that explains the experiment in greater detail. Essentially, they didn't actually freeze the photons, ie. made them stop moving, but used a different method to make the photons bounce back and forth in place. So the "color" should have remained the same.
What do you mean by "then everything is pre-determined?" In one sense, obviously the previse nature of the past events of the past you see are pre-determined, because they already happened. Or do you mean that viewing the past confirms a Deterministic view of the universe? How so?
I am just building my reasoning backwards. To understand what happens to the Photon when it stops, let's first see what happens to the photon when it moves at - well - the speed of light.
From the quickest reference I could dig thru http://www.wired.com/wired/archive/6.07/es_warp.ht ml?pg=3&topic=
So, the faster the photon moves the slower the clocks would appear to move. Then, I guess, the slower the Photon moves the faster the clock would appear to move. And when the photon STOPS, the clock must be moving INSANELY FAST. So how could it be a very brief period of time ? .. I think it is a very very very long period of time.
Guess, it all depends on which perspective you are looking at, and how you are measuring time ...
To see a world in a grain of sand, and then to step back and see the beach where the sand lies
I thought speed of light was linked to time? If this is the case, what happens to time in this experiment? Apologies if I am being a twat.
Paul.
We have the technology to create a lightsaber. I know what I'm asking Santa for Christmas now.
It was just slashdotted, and completely unable to move under the load.
I think you're missing the point.
These experiments are all a stepping stone towards genuine quantum communication. Previous experiment such as those in Paris (by firing rhubidium through a photon of light)showed that scientists can no measure certain properties of light without destroying the photon, and then re-measure it. The problem was that for quantum communication, you need to disentangle 2 separate photons from an entangled state so that any change you make to one makes ann instantaneous change to the other, it's twin if you like and that can be done it seems. But, keeping the light fixed in a certain place is one of the tricky parts. If they ever succeed at refing these crystals to the extent that a photon can be kept in a deterministic state, then all you need is 2 of these crystals - you can imagine them being placed at opposite ends of our solar system, each crystal containing your premade entangled photon bouncing back and forth, with the crystal itself locked in some kind of black box (cavity).
Presumablt the crystals would have small atomic/sub/atomic sized pin holes to fire the rhubidium or other material through one of the crystals. The the phase shif of the rhubidium caused by this firing also occurs at the other photon (because they are entangled). Then when you measure the phase shift of the second crystal, the difference is twice as great (i.e. the first phase shift plus the second phase shift0 - hence you know at the other end of the solar system, that it was fired. Now all you need is a model, to measure
according to time, t. For example, one crystal could measure every odd microsecond, the other at every even microsecond.
Now you have a unary turing machine, communicating between the stars!!!.
What's wrong with 'Does this smell like chloroform to you?'
As for the frozen light, I'm thinking this will herald a new line in novelty items of the type sold at Spencer Gifts, only to be shoved in a cupboard two days later and never seen again.
Could this lead to harvisting light? As in, freeze large areas (100-1000m3) of light and then using the light to produce energy?
Im not pretending to know what im talking about but it sounds as if one day we'll be able to cut light right out of the sky for where we dont need light, like on the moon or other planets. I was going to say antartica or the ocean but then i thought we'd prolly all die in huge freek weather storms or feeze to death.
But being able to harvest light could be a pretty cool advancement for our growing energy needs. Maybe would could harvest it with huge satelites orbiting the sun and have the light transported back as high energy lazers?
Giving IE users a taste of their own medicine since 2005 - http://pods.-is-a-geek.net/
Oops, and forgot to mention,
Though Einstein, Podosky and Rosen were able to monitor the effects of QE (Quantum Entanglement), no scientists yet know how an entangled pair of photons can have this "weird" communication.
Some suspect a quantum bridge of some kind, whatever that would be..!
I like to think it is one of natures gifts, it is wnough that we can dream of its use and who knows, maybe someday use it.
So thats why eavesdropping would be imnpossible!!!
The only hope for an eavesdropper would be to secretly take over the disentanglement process an manufacture a third photon (for his/her self)
Then however communication would break down, because inevitably, the eaves dropper would measure his/her photon, creating an extra phase shift. Now communication between the 2 law-biding parties would have a triple phase shift, so they would immediately know someone is eavesdropping and cease communication. So, QE really would be the perfect way to communicate!
And if we can hook him up to a dynamo and a generator, we've got free energy sorted. Truly, this is an age of wonders.
On the subject securing optical links, quantum crypto is an interesting aproach. It is not useful to transmit a lot of data, but can be used in secure key interchange.
More on this:
here
here
and here
Scitne aliquis remedium potimum crapulae?
http://scienceworld.wolfram.com/physics CherenkovRadiation
what implications would this have?
One actually can travel faster than the speed of light in a certain medium. I hear it is common in nuclear reactors and results in what is termed as a sonic boom of sorts when the light actually catches up to the other particles.
Reading the study you linked to, it says that when the atomic excitation that makes this possible is converted back into light, the pulse can be propagated in either a forward or backward direction.
Which should mean that you could create a sort of time-delayed mirror, wouldn't it?
Hard to see how that would be useful, except perhaps as a gag of some sort.
(Ha! Hard to see! Get it?)
Is this truly the only Earth I can live on?
You've got the right idea, but the Uncertainty Principle puts a lower bound on the mutual uncertainties in time and energy measured, ie,
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.
To-do List: Receive telemarketing call during a tornado warning. Check.
This article gives a few more details, and here is the actual press release.
"this will hopefully help the development of... ways to communicate over long distances without being eavesdropped on"
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.
They've got it all backwards. They're supposed to be working on a way to increase the speed of light. How else are we going to accomplish a practical form of interstellar travel?
Hee-hee. Dying tickles!
no, that's false. the universal speed limitation is the speed of light in a vacuum. Because light passing through matter moves slower than it does through a vacuum, it's perfectly possible to move faster than the "local" speed of light. Physicists have studied this by firing high-speed particles into crystals. Basically the particle creates a shockwave, a sort of optical equivalent of a sonic boom. It's called Cherenkov radiation if you want to look it up.
The author of this post asserts his moral rights.
Correct me if this is wrong but wound't stopped light be dark... So in turn they have effectively made very expensive and complex light switch??
Some people have posted claims that this is similar to the earlier experiments of Lene Hau, where the light pulse was indeed stored as excitations in trapped atoms (either in a BEC as in Hau's case, or in a vapor cell as in Lukin's earlier experiment).
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.
See, the stopped light isn't stored as photons... it's stored as energy in a gas, which will then produce another pulse of light identical to the incoming one when tickled with a laser. If you tried to jam too many photons in there, the gas would stop absorbing the photons, what you'd end up is a gas that's probably rather hot and has lost all the data of the incoming light pulses. Rather useless.
Photons are quanta of energy; they are quite incapable of being split or combined. Consult your local library for books on quantam physics...
The World Wide Web is dying. Soon, we shall have only the Internet.
Sorry friend, but he is correct and you are wrong.
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!
What about a man in the middle attack? You buy your entangled photon pair from my SneakyFactory. What I really sell you is two unrelated photons, while keeping their "actual" twins in my factory. Long before I delivered you your pair, I've set up my end of things to immediately record whatever comes in, and communicate it to the other photon.
Is there anything that stops this sort of attack? The only thing I can imagine is some sort of timing measurement..
-Zipwow
I don't know which is more depressing, that 2/3 didn't care enough to vote, or that 1/2 of those that did are crazy.
Off topic, admittedly, but I just googled 'tequila sunrise recipe' and here are the first three actual recipes returned:
First
Second
third
Battling Beasts
If I remember correctly, there is a very simple reason that communication via light would be secure -
In the quantum world, if you interact with the light, you change it in some way, no matter what, and since eavesdropping would involve interacting with the signal, the signal would not be exactly the same.
-- If an artist saw things as they truly are, they would cease to be an artist.
The generalized uncertainty principle basically says that two non-commuting operators have a commutator [A,B]=iC where i is the sqrt(-1), then a limit on the product of their uncertainties is delta_A*delta_B>=/2. Where delta_A is, as you indicated, a statistical calculation of the uncertainty, or standard deviation. This can be explicitly proven (and was actually one of the questions on my quantum mechanics midterm 2 years ago). (In case anyone is wondering, a commutator [A,B]=AB-BA. It is not generally zero, because A and B are operators, not variables. In programming talk, it's actually very similar to how ++c and c++ differ. Ie, it depends if the increment comes before/after the value is returned.)
This is most popular in terms of position/momentum, where the basic commutator of position/momentum operators is [x,p]=i*hbar. Thus, delta_x*delta_p>=hbar/2. Actually, the fact that [x,p]=i*hbar is one of the fundamental bases upon which most of quantum mechanics is based. (in case people are curious, in position space, momentum is referred to as the generator of translations, and thus will translate the position by some amount when it is measured. That's why position/momentum operators don't commute).
Energy and time are somewhat different. Position and momentum are specific operators. Energy is an eigenvalue of the Hamiltonian operator (sometimes). But time is a parameter, not an operator. So you cannot apply the generalized uncertainty relation here.
Now there is a rough uncertainty principle for energy/time, which goes as delta_E*delta_T>=hbar, but that isn't specifically well defined.
Finally, yes there can be local violations of conservation of energy. And this is due to the energy/time uncertainty. In other words, particles and antiparticles can spontaneously form out of the vacuum on VERY SMALL time scales. Ie, in such a small time scale, you have, at minimum, a large energy uncertainty. And thus within this uncertainty energy is conserved. Thus, local violations of energy conservation.
make world, not war
Nothing travels faster than light, with the possible exception of bad news.
The Foo people of Bar actually tried to use this fact, and built a spaceship entirely powered by bad news, but found that wherever they went they were so extremely unwelcome that there wasn't really any point in being there.