Wolf Prize Laureate in Physics 2005
Affiliation at the time of the award:
Massachusetts Institute of Technology (MIT), USA
“for groundbreaking work in atomic physics of hydrogenic systems, including research on the hydrogen maser, Rydberg atoms and Bose-Einstein condensation”.
Professor Daniel Kleppner has made fundamental contributions to atomic physics and quantum optics, mainly using hydrogen and hydrogen-like atoms. He built new devices, performed spectroscopic tests of extreme precision and investigated novel quantum phenomena.
In 1960, along with Norman Ramsey, he developed the Hydrogen maser, later used as an atomic clock of unprecedented stability. Applications of this early work range from coordination of radio-signals in long base-line radio astronomy, to satellite-based global positioning systems.
In the 1970’s Kleppner was a pioneer in the physics of Rydberg atoms. These very excited atoms have a wide range of remarkable properties. His proposal and demonstration of the inhibition of spontaneous emission from Rydberg atoms was an early step in Cavity Quantum Electrodynamics, concerned with the radiative properties of atoms in confined spaces. Kleppner’s investigations of Rydberg atom spectra in high electric and magnetic fields provided deep physical insight into the implications of classical chaos for quantum systems.
Kleppner and MIT colleague Thomas Greytak, were among the first to look for quantum degeneracy effects in ultra-cold gases. After a 20-year long quest, in 1998, they achieved Bose-Einstein condensation (BEC) in hydrogen. In the meanwhile, they developed tools instrumental to the 1995 discovery, by Eric Cornell, Carl Weiman and Wolfgang Ketterle, of BEC in alkali atoms. These include the technique of evaporative cooling, demonstrated in collaboration with Harald Hess. In their tour de force hydrogen BEC work, Kleppner and his colleagues pioneered a whole new field of physics. Bose-Einstein condensates and fermionic degenerate samples of cold atoms, currently created under various forms in many laboratories around the world, represent a new form of matter at the lowest temperatures ever achieved. Their study opens fascinating perspectives for applications in both fundamental and applied research.
In addition to his outstanding research achievements, Kleppner has been a dedicated teacher, advising many Ph.D. students who have gone on to attain prestigious positions in major universities. Some of these students have received the highest scientific awards for their own work, including a Nobel Prize (William Phillips, 1997). Kleppner, a statesman of science who is always willing to serve the common good, has served on numerous committees charged with investigating key scientific or social issues.