Optical atomic clocks

TL;DR

Optical atomic clocks have achieved unprecedented precision in timekeeping, enabling advanced scientific measurements and potential redefinition of the SI second, driven by developments in laser stabilization and frequency comb technologies.

Contribution

This paper reviews the evolution, current state, and future prospects of optical atomic clocks, highlighting technological advances and their implications for fundamental physics.

Findings

Optical clocks now approach 10^-18 precision.

Potential redefinition of the SI second based on optical standards.

Applications in tests of fundamental physics.

Abstract

In the last ten years extraordinary results in time and frequency metrology have been demonstrated. Frequency-stabilization techniques for continuous-wave lasers and femto-second optical frequency combs have enabled a rapid development of frequency standards based on optical transitions in ultra-cold neutral atoms and trapped ions. As a result, today's best performing atomic clocks tick at an optical rate and allow scientists to perform high-resolution measurements with a precision approaching a few parts in $10^{18}$. This paper reviews the history and the state of the art in optical-clock research and addresses the implementation of optical clocks in a possible future redefinition of the SI second as well as in tests of fundamental physics.