Quantum Information, 2 Volume Set, 2nd Edition

36 Quantum Logic‐Enabled Spectroscopy

Piet O. Schmidt^1,2

¹ Physikalisch‐Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany

² Leibniz Universität Hannover, Welfengarten 1, 30167 Hannover, Germany

36.1 Introduction

Laser spectroscopy (LS) has a long history and many applications in fundamental and applied science. Determining the transition frequency between electronic states in isolated atoms using LS represents the most accurate measurement of a natural constant we can currently perform. Today, these measurements approach 18 significant digits in optical clocks and can no longer be stated in hertz, since the unit hertz (based on a hyperfine transition in atomic cesium) can only be realized with an uncertainty ...