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

~~~
amirmc
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](http://en.wikipedia.org/wiki/Schrödinger's_cat)

~~~
AlisdairSH
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)?

~~~
fsniper
For intended purposes like the "Quantum repeater" I believe it does not matter
if the photons really stopped or wobbling in some very small space. For the
repeater they need to time shift photons. (IMHO, I have no idea what I'm
talking about :) )

~~~
gcb0
If they are not halted and then let go, but instead bouncing back and forth,
there's a chance that when you open the Cristal it may exit by the other side.

Also the imprinted image may be lost or fuzzier.

~~~
fsniper
It's never proposed as solving the repeater problem in full.

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cmiller1
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
> when we need to slow down light

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

~~~
cmiller1
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.

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swamp40
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
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...](http://www.tor.com/blogs/2010/10/slow-glass-seen-from-all-around-bob-
shaws-other-days-other-eyes)

~~~
swamp40
_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.

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

*mostly tongue-in-cheek

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

~~~
belorn
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.

~~~
Zergy
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?

~~~
belorn
Correct. Photons are responding to the curvature in space-time, not directly
to the gravitational field. Doing a second check, light has inertia-mass, but
not rest-mass.

~~~
czr80
> Photons are responding to the curvature in space-time, not directly to the
> gravitational field

In general relativity, space-time curvature _is_ the gravitational field, so
I'm not quite sure what distinction you're trying to draw?

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jdmitch
here is the original paper:
[http://prl.aps.org/abstract/PRL/v111/i3/e033601](http://prl.aps.org/abstract/PRL/v111/i3/e033601)

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lettergram
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?

~~~
atondwal
> 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.

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teeja
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.

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kibwen
_" 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
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).

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

~~~
xenophanes
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.

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

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qq66
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.

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datalus
I look forward to our Middle Earth future.

[http://en.wikipedia.org/wiki/Silmarils](http://en.wikipedia.org/wiki/Silmarils)

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mrt0mat0
this seems like the coolest thing in the world to see, but yet no pictures?
What does stopped light look like?

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

~~~
mrt0mat0
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?

~~~
Xurinos
My guess: The object that does not reflect light to you ceases to exist in
your vision. Nothing comes from that direction. Your brain would then attempt
to compensate -- as it does for the blind spot in both your eyes -- and fill
in the void, perhaps with a fuzzy version of continuity of whatever colors and
textures surround the object.

~~~
jerf
We don't need to make wild hypotheses about what an object that doesn't
reflect light looks like. It's so mundane we have a word for it: "black".

~~~
TallGuyShort
It would look black to a light sensor. As he says, your brain does play tricks
and fill-in-the-black more than you might think. If you have a blind-spot you
don't always perceive the absence of light - you may perceive what your brain
is expecting. There are also disorders where it does this too much. I knew a
guy who used to do things like overfill his coffee mug all the time, because
the mug kept looking empty and then suddenly it was overflowing - his brain
just expected the mug to stay empty.

~~~
jerf
A thing that absorbs light is not a "blind spot". It's _black_.

Are you on the good stuff or something? It's _black_. Just because someone
muttered "quantum" does not make this magic. It's _black_. What is so
complicated about this concept? It literally can not get much more normal than
this.

~~~
TallGuyShort
I never implied anything to do with quantum physics or "magic". I also never
said it wasn't black or an absence of light. Both I and the GP comment are
referring to how your brain fills in the gaps and causes you to think you see
things that are not there. So no light reaches you eye, yes, and that is
referred to as being "black". We're talking about what your brain would then
cause you to perceive or "see". Now what is so complicated about _that_?

~~~
jerf
"The object that does not reflect light to you ceases to exist in your vision.
Nothing comes from that direction. Your brain would then attempt to compensate
-- as it does for the blind spot in both your eyes -- and fill in the void,
perhaps with a fuzzy version of continuity of whatever colors and textures
surround the object."

This is gibberish. Unless you're high on acid, when you see a black thing,
your visual system does not go nuts trying to fill in the missing data... it
sees _black_.

You're trying to explain a phenomenon that _doesn 't exist_. Your brain does
not see a black object as a "gap"... it sees it as _black_. There's nothing
complicated to explain here. There's no "illusion". There's no weird
perceptual thing to explain, beyond the usual "what _is_ seeing red, really?"
(red for some reason being the usual color chosen for this question), which is
clearly not what is being referenced. There's no _gap_ here. No optical
illusion. Just black.

I mean, find something in your visual field that is black, and look at it for
a bit. Do you _see_ your brain "filling in the void, perhaps with a fuzzy
version of continuity of whatever colors and textures surround the object"?

The only hard thing about understanding this is that there's no hard thing.

~~~
bobbles
It would be interesting to see some ultrablack material in person
[http://www.wired.com/wiredscience/2009/03/ultrablack/](http://www.wired.com/wiredscience/2009/03/ultrablack/)

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Mr_T_
But why? Why not stop time instead?

~~~
balakk
For how long?

~~~
pbhjpbhj
Now.

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weakwire
The ultimate solution for information storage?

