A clock directly linking time to a particle's mass

Shau Yu Lan, Pei Chen Kuan, Brian Estey, Damon English, Justin M. Brown, Michael A. Hohensee, Holger Müller

Research output: Contribution to journalArticlepeer-review

89 Citations (Scopus)


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 ω0 = mc 2/ℏ, where c is the speed of light and ℏ is Planck's constant h divided by 2π. A clock referenced to ω0 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 ω0. 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.

Original languageEnglish
Pages (from-to)554-557
Number of pages4
Issue number6119
Publication statusPublished - 2013 Feb 1

All Science Journal Classification (ASJC) codes

  • General


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