Chu, Steven
Chu, Steven (1948-), an American physicist, developed a method to slow down atoms and make them easier to study. For his work with cooling and trapping atoms with laser light, Chu shared the 1997 Nobel Prize in physics with Claude Cohen-Tannoudji of France and William Daniel Phillips of the United States.
Chu attended the University of Rochester, where he received degrees in mathematics and physics. In 1970, he enrolled in graduate school at the University of California at Berkeley, with the intention of becoming a theoretical physicist. He was awarded a Ph.D. degree in 1976 and remained at Berkeley for two more years as a postdoctoral fellow. Chu joined the technical staff at Bell Laboratories (now part of Lucent Technologies) in 1978.
In the 1980's, Chu conducted experiments where he used laser beams to cool atoms to within a few millionths of a degree of absolute zero (-459.67 F or -273.15 C), causing the atoms to become nearly motionless. However, the atoms lingered for no more than half a second. To keep them for a longer time, Chu and his colleagues trapped them with optical tweezers —another intense beam of light. The atoms were then captured and could be studied or used for experiments.
These manipulation techniques may improve the accuracy of atomic clocks to within one second every 3 billion years. Such precise timing may improve the accuracy of satellite-based global-positioning systems, which are navigational aids that monitor earthquakes and volcanoes.
In 1983, Chu was named head of the quantum electronics research department. In 1987, he accepted an offer to become professor of physics and applied physics at Stanford University in Palo Alto, California. He held the chair of the physics department there from 1990 to 1993. Chu took a leave from Stanford in 2004. He then became a professor at the University of California at Berkeley and the director of the Lawrence Berkeley National Laboratory. In 2008, Stanford made him an emeritus professor. In 2009, United States President Barack Obama appointed Chu as his secretary of energy.