KEYNOTE: Review of Fieldable Optical Clocks for Precision Timekeeping Applications

Optical atomic clocks have been steadily improving in accuracy and reliability since the development of the optical frequency comb accelerated their widespread development in the early 2000s. Over the past several years, several demonstrations of fielded optical clocks have been reported based on multiple different types of atoms, optical transitions, and interrogation methods. These transportable systems enable remote frequency comparisons that can validate the performance of optical frequency standards, which is an important step toward the planned redefinition of the second in the International System of Units. Transportable optical clocks also make possible new applications like chronometric geodesy and ultra-low phase noise signal synthesis. Compact commercial versions of optical atomic clocks are also entering the precision timekeeping landscape. This talk will present a snapshot of the status of the field of transportable and commercial optical clock systems.