Daniel Kleppner

Professor Emeritus Daniel Kleppner is a principal investigator in the Research Laboratory of Electronics (RLE) at the Massachusetts Institute of Technology (MIT) and Co Director of the MIT-Harvard Center for Ultracold Atoms. . He 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. From 1987 to 2000, he was Associate Director of RLE. From 2001 to 2001, he was Interim Director of RLE.

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 Professor Kleppner was a pioneer in the physics of Rydberg atoms. These highly excited atoms have a wide range of remarkable properties. He employed these atoms to demonstrate the inhibition of spontaneous emission from atoms. This was an early step inthe development of Cavity Quantum Electrodynamics, a field concerned with the radiative properties of atoms in confined spaces. Kleppner’s investigations of Rydberg atoms in high electric and magnetic fields provided new physical insights into the connections between quantum mechanics and classical chaos.

Professor Kleppner and RLE colleague Professor 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 RLE alumni Eric Cornell and Carl Weiman, and RLE’s Wolfgang Ketterle, of BEC in alkali atoms. These include the technique of evaporative cooling, demonstrated in collaboration with Harald Hess. In their quest to observe BEC, Professor Kleppner and his colleagues helped pioneer  a major 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 these research achievements, Professor Kleppner has been a dedicated teacher, advising many Ph.D. students who have gone on to attain positions in major universities. Some of these students have received the highest scientific awards for their own work, including two Nobel Prizes (RLE alumni Carl Wieman, B.A. 1973 and William Phillips, Ph. D.  1997). In collaboration with colleagues at RLE and the Harvard Department of Physics , Professor Kleppner founded the MIT-Harvard Center for Ultracold Atoms. Professor Kleppner has also served on numerous national committees charged with investigating key scientific or social issues.