Quantum Science Seminar #12 - William D. Phillips
Автор: Quantum Science Seminar
Загружено: 2020-07-09
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William D. Phillips
JQI, NIST and University of Maryland
College Park — Maryland — U.S.A.
A New Measure: the quantum reform of the International System of Units
The metric system began with the French revolution, with the lofty ideal that measurements would be tied to the size of the earth, universally available to all. Soon, practical considerations required units of length and mass based on unique physical artifacts, a near-antithesis to universal availability. Now we are experiencing the greatest revolution in measurement since the French revolution, a revolution rooted in the atomic and quantum view of nature, again offering universal availability. The definitions of the kilogram, ampere, kelvin, and mole were all changed on 20 May 2019, and are now based on chosen and fixed values for 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. In this context I will also discuss the role of precision measurement in the history and future of quantum physics.
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