Contact info:
Lawrence Berkeley National Laboratory
One Cyclotron Road, 50A4119
Berkeley, California 94720
USA

Location: Bldg. 50A, Room 4133
Phone: (510) 486-5111
Email: schu@lbl.gov
Group website: Steven Chu Group

Research Summary

Atomic physics:
The Chu Group is continuing to develop new methods of laser cooling and trapping and to apply those methods in a variety of problems. Examples of applications include the use of an atom interferometer to measure the fine structure constant to unprecedented accuracy, the use Bose condensates in optical lattices to study many body effects related to condensed matter systems. More details -->

Biological physics:
The Chu Group applies single molecule techniques such as fluorescence resonance energy transfer, atomic force microscopy and optical tweezers, we study enzyme activity, and protein and RNA folding at the single bio-molecule level. Systems being studied include how the ribosome reads m-RNA and manufactures proteins, how vesicles fuse into the cell wall at the synapse of neurons, how cells adhere to each other via adhesive molecules, and how RNA molecules fold into active enzymes. More details -->

Technical biography

Steven Chu is the director of the Lawrence Berkeley National Laboratory and a faculty member of the University of California, Berkeley in the Physics and Molecular and Cellular Biology Departments. Formerly, he was the Theodore and Frances Geballe Professor of Physics and Applied Physics at Stanford University. Professor Chu's research is in atomic physics, polymer and biophysics.

His thesis and postdoctoral work at Berkeley, under Professor Eugene Commins, was the observation of parity non-conservation in atomic transitions in 1978. This experiment was one of the earliest atomic physics confirmations of the Weinberg-Salam-Glashow theory that unifies the weak and electromagnetic forces.   

While at Bell Laboratories he and Allen Mills did the first laser spectroscopy of positronium, the most fundamental atom (consisting of an electron and its anti-particle) in 1982. They went on to measure the 1s-2s energy difference of that atom to an accuracy of a few parts per billion, at that time, one of the most precise tests of quantum electrodynamics. They also made the first measurement of the corresponding transition in muonium, an atom consisting of m+ and an electron. Chu demonstrated that light pulses are able to propagate in absorbing medium where the velocity of the pulse can reach infinity and even become negative. (A negative velocity is defined where the peak of the pulse exits the sample before it enters the sample.)

In 1985, he led the group that showed how to first cool and then trap atoms with light. The optical trap was also used to trap microscopic particles in water: these so-called "optical tweezers" are widely used in biology. The first optical trapping was followed by the demonstration of the magneto-optic trap, the most commonly used atom trap. Since joining Stanford in 1987, Chu developed the theory of laser cooling of multi-level atoms (also done independently by Claude Cohen-Tannoudji and Jean Dalibard) in order to explain how atoms could be cooled to temperatures below the limit derived for two-level atoms. Chu and co-workers constructed the first atomic fountain that led to the current time standard used around the world. They developed an atom interferometer based on optical pulses of light to spatially separate and recombine atom matter waves. His group went on to use the atom interferometer to measure the acceleration due to gravity with a relative uncertainty of < 100 parts in a trillion. Using similar methods, his group has pioneered an atom interferometer method to measure the fine structure constant.

Using the optical tweezers, Chu invented methods to simultaneously visualize and manipulate individual bio-molecules in 1989. With this new technique, his group discovered that identical polymer molecules placed under identical conditions would follow different paths to a new equilibrium state. His group is also applying methods such as fluorescence energy transfer, optical tweezers and atomic force microscope methods to study the biology at the single molecule level. Current studies include single molecule studies of RNA folding, the synthesis of proteins by the ribosome, and vesicle fusion responsible for molecular signaling at the synapse of neural cells, the mechanics of cell adhesion, and the study of transcription initiation. 

Chu was co-winner of the Nobel Prize in Physics with William Phillips and Claude Cohen-Tannoudji (1997). In addition, he was awarded a number of prizes such as the Herbert Broida Prize for Spectroscopy (American Physical Society, 1987), Richtmyer Memorial Prize Lecturer (APS/AAPT, 1990), co-winner of the King Faisal International Prize for Science (1993), the Arthur Schawlow Prize for Laser Science (APS, 1994), the William Meggers Award for Laser Spectroscopy (Optical Society of America, 1994), the Science for Art Prize (Louis Vitton - Möet Hennesey, 1995), and. Chu received a Humboldt Senior Scientist award (1995) and the Guggenheim Fellowship (1996).

He is a member of the National Academy of Sciences, the American Philosophical Society, the American Academy of Arts and Sciences, and the Academia Sinica. He is also a foreign member of the Chinese Academy of Sciences and the Korean Academy of Science and Engineering.

Chu also serves on the Boards of the William and Flora Hewlett Foundation, the University of Rochester, NVIDIA, and the (planned) Okinawa Institute of Science and Technology. He has served on numerous advisory committees including the Executive Committee of the NAS Board on Physics and Astronomy, NIH Advisory Committee to the Director, and the NNSA Advisory Committee to the Director. Professor Chu received his A.B. and A.B. degrees in mathematics and physics from the University of Rochester, a Ph.D. in physics from the University of California, Berkeley, and a number of honorary degrees.

more about Director Chu -->