Light completely stopped for a record-breaking minute

http://www.newscientist.com/article/dn23925-light-completely-stopped-for-a-recordbreaking-minute.html?cmpid=RSS%7CNSNS%7C2012-GLOBAL%7Conline-news#.UfEVLFM6dEl

by Libertatea • 13 years ago

239 127 13 years ago

newscientist.com

mrt0mat02• 13 years ago

this seems like the coolest thing in the world to see, but yet no pictures? What does stopped light look like?

gilrain• 13 years ago

To the naked eye, nothing. If it's stopped, it can't hit your retina!

mrt0mat02• 13 years ago

my head just exploded trying to grasp this... objects don't move but i can see them, but i can only see them because of light. therefore, if light doesn't move, if the object does, can i see it on the object?

robocaptain• 13 years ago

That is the most mind-blowing thing I have read all day.

egeozcan• 13 years ago

This is so basic but incredible to think about. How do they know that it is there when it's stopped, provided that it neither has mass nor emits "something"? My brain just stopped.

hcarvalhoalves• 13 years ago

If I understood the experiment correctly, it doesn't look anything exceptional. The crystal would just turn opaque after the first laser is shut off, and when they shot the laser at it to turn it transparent again, the photons from the second laser would be re-emitted in the same trajectory. It's not really "light frozen mid-air", but rather a crystal emitting light after being hit by a laser.

DanWaterworth3• 13 years ago

What I want to know is: Does the crystal gain mass with the light stopped inside of it?

dodo53• 13 years ago

well its energy has increased, so yes, but probably not measurably.

Zergy4• 13 years ago

I though light was massless which was the reason it was able to travel at c and that anything with mass would travel at less than c?

If so then how does a massless object add weight to an object by being trapped in it.

belorn2• 13 years ago

Yes. Since light is effect by gravity, it must have a mass. The increase should however be quite small on the crystal.

correction: See below.

Zergy4• 13 years ago

I thought light was not effected by gravity but by the increased distance it had to travel due to warping effect on time/space caused by gravity?

ErsatzVerkehr2• 13 years ago

Since light is effect by gravity, it must have a mass

Sorry, this is completely false. Light is affected by gravity because gravity is really a curvature of spacetime.

* I guess "curvature of spacetime" is perhaps not the most satisfying explanation of why light is redshifted as it moves out of a gravitational potential well (i.e. if you shoot a laser from earth into space). Nonetheless the answer is still "because of relativity".

atondwal4• 13 years ago

Yes, conservation of energy.

amirmc5• 13 years ago

I don't think there's an energy -> mass -> energy transformation going on. Rather the crystal enters a different energy state while it 'has' the photon.

jdmitch• 13 years ago

here is the original paper: http://prl.aps.org/abstract/PRL/v111/i3/e033601

ANH• 13 years ago

It's nice for once to see evolutionary algorithms being used for something completely impractical.*

*mostly tongue-in-cheek

sramsay2• 13 years ago

"To break the minute barrier [they] fired a control laser at an opaque crystal, sending its atoms into a quantum superposition of two states. This made it transparent to a narrow range of frequencies. Heinze's team then halted a second beam that entered the crystal by switching off the first laser and hence the transparency."

Thus continuing my inability to understand what the fuck anyone is talking about whenever the word "quantum" is used in a sentence.

I mean, seriously. This has to be the one area of general reader science journalism in which the journalists -- having about as much as idea as I do about what the physicists are talking about -- just copy down whatever the guys in the lab coats are saying and print it.

I work in research computing. When I start talking to someone from our communications department and use a word like "interoperability," they say, "Whoa, slow down. You have to spell that out for our readers." But "quantum superposition?" Oh, what the hell.

I understand that is this very, very complicated stuff, and that they can't explain the whole thing from top to bottom every time they mention quantum mechanics. But pithy little paragraphs like this explain absolutely nothing.

jcbrand• 13 years ago

There is a Wikipedia article about "Quantum superposition". https://en.wikipedia.org/wiki/Quantum_superposition

In quantum states, you cannot know the actual state something is in unless you measure it. Beforehand, you just have different probabilities of where it might be.

A quantum superposition of two states means that there are two states the atoms can be in, with specific probabilities assigned to each state.

sramsay2• 13 years ago

Right, and issue three of this article's "multiple issues" is "This article may be too technical for most readers to understand. (April 2011)"

amirmc5• 13 years ago

My layman's reading of this.

We used a crystal that is normally opaque (not see-through) and fired laser beams at it because, well... it seemed like fun! Apparently the laser beam affected the crystal and made it see-through but only for a narrow range of light frequencies (e.g. think of a filter that only allows one colour of light through). Then we thought Hey, we know how to make this here crystal see-through for a particular wavelength of light (think 'colour' if wavelength doesn't work for you). What if we (1) made it see-through with the laser, (2) shone some of that colour light in and then (3) turned off the laser so that it's no longer see-through. I wonder what happens? <time passes> zOMG! We trapped light!

In other words, I do think it's possible to get the message across without needing to refer to 'quantum' anything. However, this article is from NewScientist and the intended audience is likely to be vaguely familiar with concepts of superposition via stories of Schrödinger's cat [1]

[1] http://en.wikipedia.org/wiki/Schrödinger's_cat

alanctgardner25• 13 years ago

Your understanding is actually pretty good (lines up with mine, at least), and I liked your explanation except for the needlessly conversational tone. Basically by only cutting things out:

We used a crystal that is normally opaque (not see-through) and fired laser beams at it [which] made it see-through but only for a narrow range of light frequencies (e.g. a filter that only allows one colour of light through). [Then] we made [the crystal] see-through with the laser, shone some of that colour light in and turned off the laser so that it's no longer see-through. We trapped light!

AlisdairSH• 13 years ago

So, the light trapped in the crystal is stationary, and not just "bouncing around" inside, where we can observe it?

I guess the question could be phrased - is the light really stopped, or just confined to a REALLY small area (but the light still vibrates, wobbles, spins, or whatever else light does when trapped in a dark place)?

guizzy• 13 years ago

I'm certainly misunderstanding something (considering they did it), but what I don't understand here is how the change of state of the crystal could have spread faster than light could escape the crystal. Is the information spreading faster than the speed of light in that case?

Jun8• 13 years ago

I think a good way to think about sentences like that is that the word quantum is short for "belonging to quantum mechanics", like how "classical gravitation" doesn't mean that there's anything classic about gravitation. The quantum quantifier is there to differentiate the superposition they mention from "classical" wave superposition.

It's very complicated stuff but not "very, very complicated" stuff, you can read Feynman's QED book (http://www.amazon.com/QED-Strange-Theory-Light-Matter/dp/069..., <$9 used with shipping) and obtain a pretty good working knowledge of things.

Arjuna2• 13 years ago

"Thus continuing my inability to understand [...]"

You will enjoy this beautiful lecture given by Dr. Feynman entitled, "Probability and Uncertainty - The Quantum Mechanical View of Nature." [1] In this lecture, he describes the double-slit experiment, which is tied to the topic of quantum superposition.

This particular section blows me away every time:

"Here are the circumstances: source, strong light source; tell me, behind which hole will I see the electron? You say, 'Well, the reason you can't tell through which hole you're going to see the electron is, it's determined by some very complicated things back here: if I knew enough about that electron - it has internal wheels, internal gears, and so forth - and that this is what determines through which hole it goes. It's 50/50 probability because, like a die, it's set sort of at random - and if I were to have studied it carefully enough, your physics is incomplete: if you get a complete enough physics, then you'll be able to predict through which hole it goes.'

That's the 'hidden variable' theory, so called.

Well, that's not possible.

It is not due to a lack of detailed knowledge that we cannot make a prediction, because I said that if I didn't turn on the light, I should get this interference pattern.

If I have a circumstance in which I get that interference pattern, then it is impossible to analyze it in terms of saying, it goes through here or here, because that curve is so simple, mathematically - a different thing than the contribution of this and this as probabilities.

So if it were possible for you to have determined through which hole it was going to go if I had the light on, the fact that I had the light on hasn't got anything to do with it! Whatever gears there are back here that you observe, which permitted you to tell me whether is was going to go through 1 or 2, you could have observed if I had the light off.

And therefore you could have told me with the light off which hole - each time an electron goes - which hole it's going to go through.

But if you can do this, then that curve would have to be represented as the sum of those that go through there and those that go through there - and it ain't.

Therefore, it's impossible to have information ahead of time as to which hole it's going to go through when the light is out - or when the light is on, or out - in a circumstance where the experiment is set up that can produce this interference pattern.

It is not a lack of unknown gears - a lack of internal complications - that makes nature have probability in it; it seems to be in some sense intrinsic.

Someone has said it this way: 'nature herself doesn't know which way the electron is going to go.' A philosopher once said (a pompous one): 'it is necessary for the very existence of science that the same conditions always produce the same result.' Well, they don't: if you set up electrons in any way - I mean, you set up the circumstance here, in the same conditions every time, and you cannot predict behind which hole you'll see the electron.

They don't - and yet the science goes on in spite of him."

[1] https://www.youtube.com/watch?v=OCFX_NHBefI

rjprins• 13 years ago

This is only true for local hidden variables. It is possible to explain this with hidden variables in broader sense. Which you could also call hidden connections.

jasonzemos• 13 years ago

I'm glad you linked to Part 6. This is the greatest QM lecture ever given.

kineticfocus• 13 years ago

I think the article struck the right balance... Stories like these first appear in the more serious media circles first, and then filter out into the mainstream. A long time ago I remember reading scientific americans that tended to be more technical then whats out in the mainstream nowadays. There's room for news sources that fit between the raw whitepapers and the mainstream.

atondwal4• 13 years ago

APS typically features important results with articles that are not only understandably by the quantitative laymen, but also do a good job of communicated content. (They're supposed to be the least common denominator for interdisciplinary physicists.)

Here's the article for this paper: http://physics.aps.org/articles/v6/80

ohwp• 13 years ago

http://xkcd.com/1240/

mathattack• 13 years ago

I almost feel like this is the one field where if you know enough to explain it, you are working in the field, not in the business of explaining it. If that makes sense...

thangalin• 13 years ago

http://davidjarvis.ca/entanglement/

I wrote a few pages explaining quantum entanglement in rudimentary terms... and without relying on math, which you'll find too much of on the Wikipedia pages.

cmiller15• 13 years ago

I work in a photonics lab and for all of the new fancy techniques you see show up in popular science publications for slowing and stopping light... they're all impractical. In the real world when we need to slow down light we still just use delay coils. Wrap tens to hundreds of kilometers of fiber into a coil (using a pump laser amplifier at some point if it gets too long) and just letting the light spin around in circles for the desired amount of time.

jberryman• 13 years ago

when we need to slow down light

Why do you need to do that? I'd never heard of "photonics" before now.

cmiller15• 13 years ago

Delaying light is sometimes used for a buffer in optical networks and signal processing, it is also used in the internal workings of certain opto-electronic devices such as optical oscillators; sometimes also used for testing and calibration of optical systems, making sure things are coming out as clean and at the same time as they do through the 'test' delay coil.

cheapsteak• 13 years ago

Could you give an example of a real world application for stopping/delaying light?

theorique• 13 years ago

Optical switching?

The trouble is that the power levels required for a nonlinear optical material are often much higher than the light beam being switched. So you might need to use a 1000W beam to switch a 1W beam (for example).

lifeformed3• 13 years ago

How big do 100km bundles of fiber get?

cmiller15• 13 years ago

The dimensions would vary depending on the form factor needed for the particular application, but a spool with a 9 inch by 9 inch spool with a 2 inch hub (which works for 1310nm applications) would hold about 120km

vacri• 13 years ago

Wouldn't that impart an improper spin on the light?

-cough-

lettergram• 13 years ago

This article was pretty poorly written, leading to a couple of questions:

1) It seems to me that the scientists could have simply stored the energy from the light for a period of time? Which would not actually be "stopping" the light.

2) I understand a super position and quantum physics, but I still have vague idea of what happened in the experiment. If I actually understand the terminology and have done various experiments, research, etc. but still don't fully understand, how would the standard reader (without further explanation) understand the article?

atondwal4• 13 years ago

It seems to me that the scientists could have simply stored the energy from the light for a period of time

Strained analogy: It's more like recording a hologram for a minute and then playing it back. It's a one-minute buffer for light, the same way we have video buffers, but for real life.

weakwire• 13 years ago

The ultimate solution for information storage?

datalus• 13 years ago

I look forward to our Middle Earth future.

http://en.wikipedia.org/wiki/Silmarils

Mr_T_• 13 years ago

But why? Why not stop time instead?

balakk• 13 years ago

For how long?

pbhjpbhj• 13 years ago

Now.

lifeformed3• 13 years ago

Someone could already be constantly stopping and resuming time. There'd be no way of knowing.

vog• 13 years ago

Indeed, maybe the guy with the rocks takes a break right now. (https://xkcd.com/505/)

swamp403• 13 years ago

I have a dream of a mirror that reflects the light of yesteryears.

You would look into it and see the reflections of the people and scene from the exact place and time as you were now - but 10, 20, 50, 100 years ago.

It would be a type of city attraction, where people would come to visit daily, so there would always be new and interesting people (and fashions) to see.

We actually have the technology to implement this right now, with video cameras, monitors and hard drives.

But the simplicity and beauty of a device that actually slows down light to accomplish this - now that would be something.

fractallyte• 13 years ago

You're thinking of 'slow glass', from Bob Shaw's short story 'Light of Other Days': http://www.tor.com/blogs/2010/10/slow-glass-seen-from-all-ar...

swamp403• 13 years ago

Analog, 1966 - Well, I guess he didn't get the idea from me, then.

Melancholy synopsis from Wiki:

While on vacation, they visit a slow glass merchant and notice the man's wife and child through the window, playing inside the house. When they enter, however, the house is deserted; only then do they realize that the window is made of slow glass, giving the lonely man his final glimpses of his long-dead wife and child.

It's funny how stories from your youth can permeate into your memories.

fudged71• 13 years ago

We actually have the technology to implement this right now, with video cameras, monitors and hard drives.

Jeez, this sounds really fun to build and exhibit...

redeemedfadi• 13 years ago

Radiolab had a segment about stopping light back in February. It's a great listen: http://www.radiolab.org/2013/feb/05/master-universe/

kibwen• 13 years ago

"Tens of seconds of light storage are needed for a device called a quantum repeater, which would stop and then re-emit photons used in secure communications, to preserve their quantum state over long distances."

That's quite a lot of latency. Assuming many repeaters, does that mean a quantum-encrypted ping from one side of the world to the other might be measured in hours?

stan_rogers• 13 years ago

Not necessarily. It's not so much that a 10-second delay will be introduced at every repeater, but that a practical system/implementation requires that a delay of up to ten seconds may be introduced when required by traffic, etc. A straight-pipe, latency-free, synchronous-only system would require a lot more infrastructure to support (analogous to the earliest direct-connection telephone systems).

xenophanes3• 13 years ago

Wait so is the story basically along the lines of, "Light hits black paint. Absorbed, stops. Comes out later." ?

xenophanes3• 13 years ago

I asked a physicist. The headline and article are both stupid but the science is good. It's like the paint thing except that when light hits paint, the paint affects the light, they interact, the information in the light gets messed up. With the fancy crystal thing they are preserving the information.

qq66• 13 years ago

This is interesting... every time I've read a "light slowed down" article over the last 10 years it's been Professor Lene Hau. This time it isn't.

teeja• 13 years ago

I strongly dislike headlines like this (which all the crappy science news digests, like New Scientist, frequently indulge in).

If light could actually be "stopped", it wouldn't be light any more. It also can't be "slowed down"; it always travels at exactly the speed of light in whatever medium it's in. OTOH, if the light's energy is absorbed by electrons, it's not "light" any more. All matter does this trick all day every day - it's not news.

This sort of sentence only sows confusion in a lot of minds.

Light completely stopped for a record-breaking minute

Related Stories