Bill Delaney: Harvard scientist stops light

Bill Delaney

CNN Boston Bureau Chief Bill Delaney reports on the recent breakthrough by a Harvard scientist who figured a way to stop light for the first time in history.

Q: How was light stopped and what are the implications of this scientific feat?

DELANEY: Harvard scientist Lene Hau has created a way in her laboratory in Cambridge, Massachusetts, to stop light for the first time in history.

When you look at a glass of water with a spoon in it, the spoon will look bent from a certain angle. In that example, what you're seeing is light slowing down. Light slows down in certain media, like water, and will create certain effects like the appearance of the bending of the spoon, but it doesn't slow down much.

About a year-and-a-half ago, Lene Hau figured out how to slow light down all the way down to 38 miles per hour from the pace light usually travels at 186,000 miles per second. That was her first breakthrough.

She's now gone a critical step farther. Using a glob of sodium atoms in an intricate device she created -- which looks like a giant pinball machine on a table, a collection of mirrors and lasers -- Hau has now shot a beam of light into this glob of sodium atoms, cooled just above absolute zero, and the light stopped.

The light actually stalled out inside the glob of sodium atoms, particularly at an instant when the light hits the sodium atoms, it is simultaneously hit with another laser -- what's called a coupling laser.

This all sounds pretty abstract, but it has a very practical application in the world of computers. If you can control the vast energy source of light, if you can stop it and therefore manipulate it, you can create -- at least theoretically -- a whole new generation of super-fast computers, lightning-fast computers, known as quantum computers.

Instead of storing information on a disk, these quantum computers would store and transmit information along optical fiber. Light would store information.

Q: Would these quantum computers be available to the average consumer?

DELANEY: Like most technological breakthroughs, they would likely start out on a more sophisticated level of computer, a type of new generation of super computers.

But like so much technology, what starts out on a very advanced level not accessible to the ordinary person could eventually work its way down to the average person using a computer. What it works out to is using optical fiber and light technology to store and send information. Light is a much more powerful source and could store much more information and move at inconceivably fast speeds.

Another advantage of light-based computers, scientists tell us, is that it will be virtually impossible to break into this system and steal information.

It's all very complex, but it all boils down to conceivably a new generation of computers almost infinitely faster than anything we've ever seen.

And it all starts on a lab on the shores of the Charles River in Cambridge, Massachusetts, where for the first time in history of science light has been stopped.

Q: How long has this scientist been trying to stop light?

DELANEY: Lene Hau has actually been working on experiments with light for about three or four years, which is not a very long time when you're talking about experimental science. She's worked very long hours, and had a lot of hit-and-mostly-miss experiments until about a year-and-a-half ago when they figured out a way to slow light down.

It is interesting to ask what happens to light when it's slowed down and when it's stopped.

Q: That's very interesting: What happens to light when it stops? Does it disappear?

DELANEY: It's not too easy for a layman to grasp when Lene Hau begins to talk about the different levels of the atom in explaining how light is stopped.

But, in effect, light does disappear when it's stopped. It stalls out. It can be reactivated by, in effect, opening a gate. I mentioned the coupling laser.

The cloud of sodium atoms must be intermingled with this coupling laser to actually stop the light. The coupling laser slams down into the cloud of sodium atoms to stop the light. When the coupling laser is then slammed off, the light again reactivates itself and begins to travel again.

That's the bare bones of how this works.

Q: What are the ethical concerns in the scientific community with stopping light?

DELANEY: I asked Lene Hau: Are you changing reality? Are you taking this basic fundamental property of all reality -- light -- and obliterating what exists in existing light?

She said what they are doing is a kind of magic, but on the other hand, it needs to be understood that we are dealing with very, very tiny quantities of light. It's not as if this can be extrapolated to mean that the light flowing off a person's face or off a tree could ultimately be captured or stopped -- almost like some kind of science-fiction manipulation of light.

This is a very limited control of light involving this super-cooled sodium that eventually may have implications for super-fast computers.

Harvard Dept. of Physics Faculty - Hau

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