Re: [rumori] pho: NYT: Stop Light

From: Chris Ball (
Date: Fri Jan 19 2001 - 12:13:42 PST

It's so musical!

I wonder if they stopped it for 4 minutes 33 seconds.

I think quantum computing would be the tip of the iceberg.

----- Original Message -----
From: "Don Joyce" <>
To: "mark hosler" <>
Sent: Friday, January 19, 2001 9:31 AM
Subject: [rumori] pho: NYT: Stop Light

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> >Date: Thu, 18 Jan 2001 09:28:29 EST
> >Subject: pho: NYT: Stop Light
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> >
> >Quantum computing in your lifetime. Fiber (or other photonic conduits?)
> >everywhere. Extraordinary.
> >
> >Really.
> >
> >
> >January 18, 2001
> >Scientists Bring Light to Full Stop, Hold It, Then Send It on Its Way
> >
> >Researchers say they have slowed light to a dead stop, stored it and then
> >released it as if it were an ordinary material particle.
> >
> >The achievement is a landmark feat that, by reining in nature's swiftest
> >most ethereal form of energy for the first time, could help realize what
> >now theoretical concepts for vastly increasing the speed of computers and
> >security of communications.
> >
> >Two independent teams of physicists have achieved the result, one led by
> >Lene Vestergaard Hau of Harvard University and the Rowland Institute for
> >Science in Cambridge, Mass., and the other by Dr. Ronald L. Walsworth and
> >Mikhail D. Lukin of the Harvard-Smithsonian Center for Astrophysics, also
> >Cambridge.
> >
> >Light normally moves through space at 186,000 miles a second. Ordinary
> >transparent media like water, glass and crystal slow light slightly, an
> >effect that causes the bending of light rays that allows lenses to focus
> >images and prisms to produce spectra.
> >
> >Using a distantly related but much more powerful effect, the
> >team first slowed and then stopped the light in a medium that consisted
> >specially prepared containers of gas. In this medium, the light became
> >fainter and fainter as it slowed and then stopped. By flashing a second
> >through the gas, the team could essentially revive the original beam.
> >
> >The beam then left the chamber carrying nearly the same shape, intensity
> >other properties it had when it entered. The experiments led by Dr. Hau
> >achieved similar results with closely related techniques.
> >
> >"Essentially, the light becomes stuck in the medium, and it can't get out
> >until the experimenters say so," said Dr. Seth Lloyd, an associate
> >of mechanical engineering at the Massachusetts Institute of Technology
who is
> >familiar with the work.
> >
> >Dr. Lloyd added, "Who ever thought that you could make light stand
> >
> >He said the work's biggest impact could come in futuristic technologies
> >called quantum computing and quantum communication. Both concepts rely
> >heavily on the ability of light to carry so-called quantum information,
> >involving particles that can exist in many places or states at once.
> >
> >Quantum computers could crank through certain operations vastly faster
> >existing machines; quantum commmunications could never be eavesdropped
> >For both these systems, light is needed to form large networks of
> >But those connections are difficult without temporary storage of light, a
> >problem that the new work could help solve.
> >
> >A paper by Dr. Walsworth, Dr. Lukin and three collaborators 'До Dr. David
> >Phillips, Annet Fleischhauer and Dr. Alois Mair, all at Harvard-
> >'До is scheduled to appear in the Jan. 29 issue of Physical Review
> >
> >Citing restrictions imposed by the journal Nature, where her report is to
> >appear, Dr. Hau refused to discuss her work in detail.
> >
> >Two years ago, however, Nature published Dr. Hau's description of work in
> >which she slowed light to about 38 miles an hour in a system involving
> >of light shone through a chilled sodium gas.
> >
> >Dr. Walsworth and Dr. Lukin mentioned Dr. Hau's new work in their paper,
> >saying she achieved her latest results using a similarly chilled gas. Dr.
> >Lukin cited her earlier work, which Dr. Hau produced in collaboration
> >Dr. Stephen Harris of Stanford University, as the inspiration for the new
> >experiments.
> >
> >Those experiments take the next step, stopping the light's propagation
> >completely.
> >
> >"We've been able to hold it there and just let it go, and what comes out
is t
> >he same as what we sent in," Dr. Walsworth said. "So it's like a freeze
> >frame."
> >
> >Dr. Walsworth, Dr. Lukin and their team slowed light in a gas form of
> >rubidium, an alkaline metal element.
> >
> >The deceleration of the light in the rubidium differed in several ways
> >how light slows through an ordinary lens. For one thing, the light dimmed
> >it slowed through the rubidium.
> >
> >Another change involved the behavior of atoms in the gas, which developed
> >sort of impression of the slowing wave.
> >
> >This impression, actually consisting of patterns in a property of the
> >called their spin, was a kind of record of the light's passing and was
> >to allow the experimenters to revive or reconstitute the original beam.
> >
> >Both Dr. Hau's original experiments on slowing light, and the new ones on
> >stopping it, rely on a complex phenomenon in certain gases called
> >electromagnetically induced transparency, or E.I.T.
> >
> >This property allows certain gases, like rubidium, that are normally
> >to become transparent when specially treated.
> >
> >For example, rubidium would normally absorb the dark red laser light used
> >Dr. Walsworth and his colleagues, because rubidium atoms are easily
> >by the frequency of that light.
> >
> >But by shining a second laser, with a slightly different frequency,
> >the gas, the researchers rendered it transparent.
> >
> >The reason is that the two lasers create the sort of "beat frequency"
> >occurs when two tuning forks simultaneously sound slightly different
> >
> >The gas does not easily absorb that frequency, so it allows the light to
> >through it; that is, the gas becomes transparent.
> >
> >But another property of the atoms, called their spin, is still sensitive
> >the new frequency. Atoms do not actually spin but the property is a
> >quantum-mechanical effect analagous to a tiny bar magnet that can be
> >by the light.
> >
> >As the light passes through, it alters those spins, in effect flipping
> >Though the gas remains transparent, the interaction serves as a friction
> >weight on the light, slowing it.
> >
> >Using that technique, Dr. Hau and Dr. Harris in the earlier experiment
> >light to a crawl. But they could not stop it, because the transparent
> >"window" in the gas became increasingly narrower, and more difficult to
> >through, as the light moved slower and slower.
> >
> >In a recent theoretical advance, Dr. Lukin, with Dr. Suzanne Yelin of
> >Harvard-Smithsonian and Dr. Michael Fleischhauer of the University of
> >Kaiserslautern in Germany, discovered a way around this constraint.
> >
> >They suggested waiting for the beam to enter the gas container, then
> >reducing the intensity of the second beam.
> >
> >The three physicists calculated that this procedure would narrow the
> >slowing the first beam, but also "tune" the system so that the beam
> >passes through.
> >
> >The first beam, they theorized, should slow to an infinitesimally slow
> >finally present only as an imprint on the spins, with no visible light
> >remaining. Turning the second beam back on, they speculated, should
> >reconstitute the first beam.
> >
> >The new experiments bore those ideas out.
> >
> >"The light is actually brought to a stop and stored completely in the
> >Dr. Harris said. "There's no other way to do that. It's been done 'До
> >very
> >convincingly, and beautifully."
> >
> >Copyright 2001 The New York Times Company
> >

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