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Quantum Mechanic

Nobel Laureate Steven Chu is working to save the earth one molecule at a time.

by William Nakayama

ou would think that a guy who won a Nobel Prize for cooling something as tiny as a single sodium atom down to 240 millionth of a degree above absolute zero by zapping it with lasers would be able to cool something as big as the earth.

     So does Steven Chu. Like many greats rats Chu is motivated by the grand ambition of saving the earth from the center of the clean energy movement. That's why in 2004 he left a prestigious research and teaching post at Stanford to head up a multi-disciplinary effort at UC Berkeley to develop technologies aimed at reversing climate change.

     Chu's altruism isn't limited to concerns on the planetary scale. His other motivation for jumping across San Francisco Bay to Cal was to help his alma mater retain its traditional leadership in the physical sciences. Public schools like Cal, he felt, were falling behind well-endowed private universities like Stanford, and he wanted to help reverse that trend as well.

     Chu's official title is Professor of Physics and Molecular and Cellular Biology and Director of the Lawrence Berkeley National Laboratory. In addition to the scientists at Lawrence Berkeley, Steven Chu commands the resources of oil industry giant BP and the University of Illinois under a research pact that includes a new $400 million Lawrence Berkeley lab to expand energy-related molecular work. A $160 million Energy Biosciences Institute is also being built to house a solar energy program personally headed by Chu.

     Chu's most famous work — the work that won him the 1997 Nobel Prize in Physics — focused on cooling and trapping sodium atoms. The Prize recognized him for pioneering a novel technique for cooling them down to 240-millionth of a degree above absolute zero. What takes the feat beyond ordinary comprehension is how it was done: by firing an array of six lasers at the target atoms.

     To try to diminish the energy of atoms by bombarding them with concentrated beams of electromagnetic energy is totally counter-intuitive to anyone with a smattering of physics knowledge. But hardcore physicists like Chu know that matter and energy follow different rules on the atomic level. While ordinary objects appear to absorb energy along an uninterrupted continuum, individual atoms are governed by the laws of quantum mechanics which restrict energy changes to discrete jumps. Chu ingeniously exploited Doppler shifts in wavelengths produced by moving objects to create what he calls an "optical molasses" effect. The lasers are tuned to a wavelength which, when doppler-shifted, can be absorbed by atoms moving toward the laser, thereby progressively slowing them until most of their kinetic energy has been lost. The laser has no effect on atoms with little motion along the laser's axis.

     In devising his elegant solution to the cooling problem, Chu attained something of a holy grail of atomic physics — a method for trapping high densitities of atoms into relatively small spaces. Chu came up with the simple but novel approach of cooling atoms first before trying to trap them. This was a revelation to scores of scientists who had been trying without success to do it in reverse order.

     Chu's breakthrough also created a bonanza for inventors and engineers working on everything from more precise atomic clocks to better equipment for locating mineral deposits from airplanes. Laser-cooling is still in its infancy, but its potential to create and revolutionize new industries could ultimately rival the laser.

     Steve Chu was born February 28, 1948 in St Louis, Missouri where his China-born father was teaching chemical engineering. He grew up in Garden City, New York. After kindergarten he began building model airplanes, then graduated to erector sets in the fourth grade. That led to chemistry experiments and model rocketry. Chu did also participate in sports like touch football, baseball, basketball and tennis, but his life work would be an extension of his boyhood love of tinkering.

     As a freshman at Rochester he assumed that he would become a theoretical physicist, generally considered the field's more glamorous side. For graduate school Chu chose Berkeley with an eye toward following in the footsteps of the great theoretical physicists, especially Feynman. As he entered the upper division he reconciled himself to his natural love for experimental physics with all its extravagant tinkering. One of his post-doc Berkeley experiments involving table-top lasers ignited his interest in working with what was then an exciting experimental technology.

     After finishing both his graduate and post-doc, Chu moved to Bell Laboratories in 1978. By 1983 he had established himself as head of Bell Labs' Quantum Electronics Research Department at Holmdel, New Jersey. That was where Steve Chu met Art Ashkin. Ashkin had pursued efforts to trap atoms with lasers, but had had funding cut four years earlier. In 1987 he left Bell Labs and became a professor of Physics at Stanford where he chaired the Physics Department from 1990-1993 and 1999-2001. He was appointed as the director of Lawrence Berkeley National Laboratory in 2004.

     When he isn't immersed in molecular physics, Chu gets physical by swimming, cycling and playing a little baseball. Shortly after Chu received the Nobel Prize he married Jean Chu, an Oxford-trained physicist and the ex-wife of a Stanford colleague.

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STEVEN CHU

Quantum Mechanic