We review experimental progress on optical atomic clocks and frequency transfer, and
consider the prospects of using these technologies for geodetic measurements. Today …

Quantum physics has intrigued scientists and philosophers alike, because it challenges our
notions of reality and locality—concepts that we have grown to rely on in our macroscopic …

Extremely narrow optical resonances in cold atoms or single trapped ions can be measured
with high resolution. A laser locked to such a narrow optical resonance could serve as a …

The proton is the primary building block of the visible Universe, but many of its properties—
such as its charge radius and its anomalous magnetic moment—are not well understood …

In the past decade we have witnessed remarkable advances associated with the frequency
stabilization of the comb present in the output of a mode-locked femtosecond laser. While …

1.1. Background This article reports work carried out under the auspices of the Committee
on Data for Science and Technology (CODATA) Task Group on Fundamental Constants. 1 It …

We have measured the 1 S–2 S transition frequency in atomic hydrogen via two-photon
spectroscopy on a 5.8 K atomic beam. We obtain f 1 S–2 S= 2 466 061 413 187 035 (10) Hz …

Recently there has been a remarkable synergy between the technologies of precision laser
stabilization and mode-locked ultrafast lasers. This has resulted in control of the frequency …

Nobel Lecture: Passion for precision* Page 1 Nobel Lecture: Passion for precision*
Theodor W. Hänsch† Max-Planck Institute of Quantum Optics, Garching, Germany and …

1.1. Background This paper gives the complete 2006 CODATA self-consistent set of
recommended values of the fundamental physical constants and describes in detail the …