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."

Who wants to stop light?

Now if they could only figure out how to stop SPAM

Re:Who wants to stop light?

Is there a such thing as light spam? Because if there is, you know, maybe it would easier to start with that...

Yep. [spam.com]

I can't wait for the future development...

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?

Re:I can't wait for the future development...

"thrust me"

Is that going to be your pickup line at said bar?

Let there be light, baby.

Is that going to be your pickup line at said bar?

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.

Man...Imagine the vaccuum

Oh...wait. Voids allow light to travel faster. shame on me. What color is stopped light if it retains its energy?

Color == frequency

Light doesn't actually have "color". Color is our perception of the wavelength of the light. There's another article on BBC [bbc.co.uk] 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.

Re:Color != frequency

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!

Re:Man...Imagine the vaccuum

Octarine, of course

Okay...

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?

Well you could have found it

Like I did here. [lanl.gov]

Stopped light...

Makes me think of a physics joke.

Q: What is the difference between stopped light and darkness?

A: You know where darkness is.

Speaking of light and darkness...

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."

Reminds me of another physics joke...

Officer: "Do you know how fast you were going?"

Heisenberg: "No, but I know exactly where I am!"

Re:Actually uncertainty applies here.

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.

Re:Stopped light...

"If this sticker appears blue, you're driving too fast." --A red bumpersticker

Very interesting...

development of quantum computers and ways to communicate over long distances without being eavesdropped on.

I thought that light is a visual thing. How does one "eavesdrop" on light?

Back to Entanglement.

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!!!.

Man in the middle?

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

Apparently, there is energy loss

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.

Re:Apparently, there is energy loss

Well, "destroying its energy" would be a rather major accomplishment, if I remember my highschool lessons regarding conservation of energy...

Interesting note/errata

Harnessing light particles to store and process data could aid the still distant goal of so-called quantum computers, as well as methods for communicating information over long distances without risk of eavesdropping.

But today the NSA's snooping capabilities are in jeopardy, undermined by advances in telecommunications technology. Much of the information the agency once gleaned from the air waves now travels in the form of light beams through fiber-optic cables crisscrossing continents and ocean floors. That shift has forced the NSA to seek new ways to gather intelligence -- including tapping undersea cables, a technologically daunting, physically dangerous and potentially illegal task.

In the mid-1990s, the NSA installed one such tap, say former intelligence officials familiar with the covert project. Using a special spy submarine, they say, agency personnel descended hundreds of feet into one of the oceans and sliced into a fiber-optic cable. The mixed results of the experiment -- particularly the agency's inability to make sense of the vast flood of data unleashed by the tap -- show that America's pre-eminent spy service has huge challenges to overcome if it hopes to keep from going deaf in the digital age.

Details of the NSA cable-tapping project are sketchy. Individuals who confirm the tap won't specify where or when it occurred. It isn't known whether the cable's operator detected the intrusion, though former NSA officials say they believe it went unnoticed. Nor is it known whether the NSA has attempted other taps since. Efforts to intercept all sorts of signals -- ranging from military radar to international phone calls -- are among the most highly classified U.S. government operations. Leaking information about interception methods is a federal crime punishable by imprisonment.
[Source [politrix.org]]

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 [com.com]

NSA Tapping Underwater Fiber Optics [slashdot.org]

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.

Re:Interesting note/errata

Good old fashioned history [slashdot.org]... Now only I could get my damn old UID [slashdot.org] back... Taco?

Submarine cable interception

Submarine cables now play a dominant role in international telecommunications, since - in contrast to the limited bandwidth available for space systems - optical media offer seemingly unlimited capacity. Save where cables terminate in countries where telecommunications operators provide Comint access (such as the UK and the US), submarine cables appear intrinsically secure because of the nature of the ocean environment. 49. In October 1971, this security was shown not to exist. A US submarine, Halibut, visited the Sea of Okhotsk off the eastern USSR and recorded communications passing on a military cable to the Khamchatka Peninsula Halibut was equipped with a deep diving chamber, fully in view on the submarine's stern. The chamber was described by the US Navy as a "deep submergence rescue vehicle". The truth was that the "rescue vehicle" was welded immovably to the submarine. Once submerged, deep-sea divers exited the submarine and wrapped tapping coils around the cable. Having proven the principle, USS Halibut returned in 1972 and laid a high capacity recording pod next to the cable. The technique involved no physical damage and was unlikely to have been readily detectable.

The Okhotsk cable tapping operation continued for ten years, involving routine trips by three different specially equipped submarines to collect old pods and lay new ones; sometimes, more than one pod at a time. New targets were added in 1979. That summer, a newly converted submarine called USS Parche travelled from San Francisco under the North Pole to the Barents Sea, and laid a new cable tap near Murmansk. Its crew received a presidential citation for their achievement. The Okhotsk cable tap ended in 1982, after its location was compromised by a former NSA employee who sold information about the tap, codenamed IVY BELLS, to the Soviet Union. One of the IVY BELLS pods is now on display in the Moscow museum of the former KGB. The cable tap in the Barents Sea continued in operation, undetected, until tapping stopped in 1992.

During 1985, cable-tapping operations were extended into the Mediterranean, to intercept cables linking Europe to West Africa. (30) After the cold war ended, the USS Parche was refitted with an extended section to accommodate larger cable tapping equipment and pods. Cable taps could be laid by remote control, using drones. USS Parche continues in operation to the present day, but the precise targets of its missions remain unknown. The Clinton administration evidently places high value on its achievements, Every year from 1994 to 1997, the submarine crew has been highly commended.(31) Likely targets may include the Middle East, Mediterranean, eastern Asia, and South America. The United States is the only naval power known to have deployed deep-sea technology for this purpose.

Miniaturised inductive taps recorders have also been used to intercept underground cables.(32) Optical fibre cables, however, do not leak radio frequency signals and cannot be tapped using inductive loops. NSA and other Comint agencies have spent a great deal of money on research into tapping optical fibres, reportedly with little success. But long distance optical fibre cables are not invulnerable. The key means of access is by tampering with optoelectronic "repeaters" which boost signal levels over long distances. It follows that any submarine cable system using submerged optoelectronic repeaters cannot be considered secure from interception and communications intelligence activity.

Re:Interesting note/errata

That may be how traditional optical communications works. Quantum crypto, otoh, relies on the light being put in a certain polarization state by the sender. It's designed so that a stream of single photons go from sender to receiver; there can be no equipment in-between. If an intermediary views this photon en-route, it disturbs the polarization seen by the receiver. Because of the way the sender and receiver can agree on which photons were correctly measured, any aberrations (intercepted photons) are discarded. The most you can hope for is a denial-of-service.

Here's a better explanation [dartmouth.edu] than I can muster.

Re:Interesting note/errata

No. The lack of eavesdropping refers to the quantum properties of entangled photons used to encrypt communications in a theoretically unbreakable way. See here [eetimes.com]. There was also a slashdot story on this a few years ago.

Light RAM

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!

Another article

BBC News [bbc.co.uk] 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."

Other Days, Other Eyes

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.

Re:Other Days, Other Eyes

Interesting story, I grant you, but if such a thing existed, you'd have to wonder at the temperature the glass would reach after absorbing light for a few years. It'd be possible to do something similar to it using other methods, but I doubt the possibility of doing it using anything similar to the methods described in the book.

More links

More detailed articles about the research can be found here [hackensackhigh.org] or here [sciencenews.org].

Larkin's article itself is here [lanl.gov].

Any physics nerds want to explain it to us?

Re:More links

The light beam is stored (in gas atoms) rather than stopped. It's a bit like sending an e-mail - you don't get the same electrons that were sent to you from the other person's computer, but the electrons that come down your telephone line/DSL/cable are identical in every respect.

Re:If we stopped light,

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.

Darn darn darn

Why were there no pictures of this stopped light? .. oh wait

SF story with slow-light windowpanes?

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.

Re:SF story with slow-light windowpanes?

Bob Shaw, Other Days, Other Eyes. A poster above mentioned it.

Re:SF story with slow-light windowpanes?

The Light of Other Days [amazon.com] is by Steven Baxter and Arthur C. Clark.

Free energy!

According to the Slashdot summary, it is apparently possible to destroy energy!!! Issac Newton may turn in his grave...

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.

Is brief really very long time for the Photon?

have been able to stop light for a very brief period of time

a very brief period of time ? .. I think it depends on what perspective you look at it from.

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 [wired.com] http://www.wired.com/wired/archive/6.07/es_warp.ht ml?pg=3&topic=

Einstein also predicted that time itself must slow down for objects in motion.

The faster you move, the slower your clocks would appear to tick - relative to someone watching from a remote location. If you could actually reach light speed, time would crawl to a stop. It's wildly counterintuitive, but experiments have proved it true.

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 ...

Re:Is brief really very long time for the Photon?

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

So far, Hau and her team report the longest storage time for pulses--about a millisecond. By then, random atomic motion had washed out most pulse information, the researchers suspect. The Harvard-Smithsonian team reports that its pulses' information is erased partly because atoms escape from the region lit by the coupling laser.

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...

Finally

We have the technology to create a lightsaber. I know what I'm asking Santa for Christmas now.

The light particle was never frozen

It was just slashdotted, and completely unable to move under the load.

Harvest time

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?

A few more details

This article [optics.org] gives a few more details, and here [iop.org] is the actual press release.

Say what?

"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.

No, no

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?

Who turned out the lights!

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??

What they're actually doing

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.