An Atomic Clock with 10 –18 Instability

Abstract

Tick, Tick, Tick…: Many aspects of everyday life from communication to navigation rely on the precise ticking of the microwave transitions of the atoms in atomic clocks. Optical transitions occur at much higher frequency and so offer the opportunity to reduce the scale of the ticks even more. Hinkley et al. (p. 1215 , published online 22 August; see the Perspective by Margolis ) compare the ticking of two optical clocks and report an instability near the 10 ⁻¹⁸ level. Such performance will improve tests of general relativity and pave the way for a redefinition of the second.