Quantum Measurement Division, Physical Measurement Laboratory
National Institute of Standards and Technology

The metric system, officially the “International System of Units” or SI has its roots in the French revolution.  Recently we have experienced the greatest revolution in measurement units since the French revolution.  The quantum nature of matter now provides new definitions of the kilogram, ampere, kelvin, and mole.  These quantities are defined by fixing values for the most fundamental quantum constant, Planck’s constant; the quantum of electric charge;  Boltzmann’s constant;  and Avogadro’s number. I will explain how this is possible, why it was necessary, and speculate about future changes in the SI that may take advantage of features of the Second Quantum Revolution.

William D. Phillips received a B.S. from Juniata College in 1970, and a Ph.D. from MIT in 1976;  after two years as a postdoc at MIT, he joined NIST to work on precision electrical measurements and fundamental constants.  There, he founded NIST’s Laser Cooling and Trapping Group, and later was a founding member of the Joint Quantum Institute, a cooperative research organization of NIST and the University of Maryland.  His research group has developed some of the principal techniques used for laser-cooling and cold-atom experiments in laboratories around the world.  Atomic fountain clocks, based on the work of this group, are now the primary standards for world timekeeping.  The group also studies quantum information applications of cold atoms.

Dr. Phillips is a fellow of the American Physical Society, the American Association for the Advancement of Science, and the American Academy of Arts and Sciences.  He is a Fellow and Honorary Member of OPTICA, a member of the National Academy of Sciences, the Pontifical Academy of Sciences, and a corresponding member of the Mexican Academy of Sciences.  In 1997, Dr. Phillips shared the Nobel Prize in Physics “for development of methods to cool and trap atoms with laser light.