Measuring Mass in Seconds

Department of Quantum Science, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200, Australia.
Science (Impact Factor: 33.61). 02/2013; 339(6119):532-533. DOI: 10.1126/science.1232923
Source: PubMed
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    ABSTRACT: Historically, time measurements have been based on oscillation frequencies in systems of particles, from the motion of celestial bodies to atomic transitions. Relativity and quantum mechanics show that even a single particle of mass m determines a Compton frequency ω(0 )= mc(2)/ ħ, where c is the speed of light and ħ is the reduced Planck constant. A clock referenced to ω(0) would enable high-precision mass measurements and a fundamental definition of the second. We demonstrate such a clock using an optical frequency comb to self-reference a Ramsey-Bordé atom interferometer and synchronize an oscillator at a subharmonic of ω(0). This directly demonstrates the connection between time and mass. It allows measurement of microscopic masses with 4 × 10(-9) accuracy in the proposed revision to SI units. Together with the Avogadro project, it yields calibrated kilograms.
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