Arthur Matveev

TL;DR: The 1S-2S transition frequency in atomic hydrogen via two-photon spectroscopy on a 5.8 K atomic beam is measured, with improvement to a fractional frequency uncertainty of 4.2 × 10(-15) arises mainly from an improved stability of the Spectroscopy laser, and a better determination of the main systematic uncertainties.

TL;DR: The authors obtained the size of the proton using very accurate spectroscopic measurements of regular hydrogen using an asymmetric fit function, which eliminates line shifts from quantum interference of neighboring atomic resonances.

TL;DR: In this paper, the authors achieved a 0.5 Hz optical beat note linewidth with a frequency drift at 972 nm between two external cavity diode lasers independently stabilized to two vertically mounted Fabry-P\'erot (FP) reference cavities with a finesse of 400 000.

TL;DR: The frequency of the extremely narrow 1S-2S two-photon transition in atomic hydrogen is measured using a remote cesium fountain clock with the help of a 920 km stabilized optical fiber with a relative uncertainty of 4.5×10(-15).

TL;DR: Huber et al. as discussed by the authors measured the hydrogen-deuterium isotope shift via two-photon spectroscopy of the $1S\ensuremath{-}2S$ transition, obtaining 670 994 334 606(15) Hz.