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Dolores Beasley
Headquarters, Washington              May 21, 2003
(Phone: 202/358-1753)

Jane Platt
Jet Propulsion Laboratory, Pasadena, Calif.
(Phone: 818/354-0880)

RELEASE:  03-176

FROZEN LIGHT: COOL NASA RESEARCH HOLDS PROMISE

     NASA-funded research at Harvard University, Cambridge, 
Mass., that literally stops light in its tracks, may someday 
lead to breakneck-speed computers that shelter enormous 
amounts of data from hackers.

The research, conducted by a team led by Dr. Lene Hau, a 
Harvard physics professor, is one of 12 research projects 
featured in a special edition of Scientific American 
entitled "The Edge of Physics," available through May 31.

In their laboratory, Hau and her colleagues have been able 
to slow a pulse of light, and even stop it, for several-
thousandths of a second. They've also created a roadblock 
for light, where they can shorten a light pulse by factors 
of a billion.

"This could open up a whole new way to use light, doing 
things we could only imagine before," Hau said. "Until now, 
many technologies have been limited by the speed at which 
light travels."

The speed of light is approximately 186,000 miles per second 
(670 million miles per hour). Some substances, like water 
and diamonds, can slow light to a limited extent. More 
drastic techniques are needed to dramatically reduce the 
speed of light. Hau's team accomplished "light magic" by 
laser-cooling a cigar-shaped cloud of sodium atoms to one-
billionth of a degree above absolute zero, the point where 
scientists believe no further cooling can occur. Using a 
powerful electromagnet, the researchers suspended the cloud 
in an ultra-high vacuum chamber, until it formed a frigid, 
swamp-like goop of atoms.

When they shot a light pulse into the cloud, it bogged down, 
slowed dramatically, eventually stopped, and turned off. The 
scientists later revived the light pulse and restored its 
normal speed by shooting an additional laser beam into the 
cloud.

Hau's cold-atom research began in the mid-1990s, when she 
put ultra-cold atoms in such cramped quarters they formed a 
type of matter called a Bose-Einstein condensate. In this 
state, atoms behave oddly, and traditional laws of physics 
do not apply. Instead of bouncing off each other like bumper 
cars, the atoms join together and function as one entity. 

The first slow-light breakthrough for Hau and her colleagues 
came in March 1998. Later that summer, they successfully 
slowed a light beam to 38 miles per hour, the speed of 
suburban traffic. That's two million times slower than the 
speed of light in free space. By tinkering with the system, 
Hau and her team made light stop completely in the summer of 
2000. 

These breakthroughs may eventually be used in advanced 
optical-communication applications. "Light can carry 
enormous amounts of information through changes in its 
frequency, phase, intensity or other properties," Hau said. 
When the light pulse stops, its information is suspended and 
stored, just as information is stored in the memory of a 
computer. Light-carrying quantum bits could carry 
significantly more information than current computer bits. 
Quantum computers could also be more secure by encrypting 
information in elaborate codes that could be broken only by 
using a laser and complex decoding formulas.

Hau's team is also using slow light as a completely new 
probe of the very odd properties of Bose-Einstein 
condensates. For example, with the light roadblock the team 
created, they can study waves and dramatic rotating-vortex 
patterns in the condensates. 

The Harvard research team includes Hau; Drs. Zachary Dutton, 
Chien Lieu, Brian Busch and Michael Budde; and graduate 
students Christopher Slowe, Naomi Ginsberg and Cyrus 
Behroozi. More information about Hau's research is available 
on the Internet, at:

http://www.physics.harvard.edu/fac_staff/hau.html

For information about NASA's Fundamental Physics Program on 
the Internet, visit:

http://spaceresearch.nasa.gov

http://funphysics.jpl.nasa.gov

Hau conducts research under NASA's Fundamental Physics in 
Physical Sciences Research Program, part of the agency's 
Office of Biological and Physical Research, Washington. 
NASA'S Jet Propulsion Laboratory, Pasadena, Calif., a 
division of the California Institute of Technology, 
Pasadena, manages the Fundamental Physics program.

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