Precision spectroscopy with two correlated atoms

TL;DR

This paper presents techniques for high-precision laser spectroscopy using two trapped ions, leveraging entangled states or common phase noise to achieve long coherence times, and demonstrates applications in measuring atomic properties and laser linewidth.

Contribution

It introduces methods utilizing decoherence-free subspaces and phase noise correlation for enhanced spectroscopy with two ions, expanding beyond entanglement-based approaches.

Findings

Successful measurement of the electric quadrupole moment of 40Ca+

Linewidth measurement of an ultrastable laser with two ions

Demonstration of long coherence times in two-ion spectroscopy

Abstract

We discuss techniques that allow for long coherence times in laser spectroscopy experiments with two trapped ions. We show that for this purpose not only entangled ions prepared in decoherence-free subspaces can be used but also a pair of ions that are not entangled but subject to the same kind of phase noise. We apply this technique to a measurement of the electric quadrupole moment of the 3d D5/2 state of 40Ca+ and to a measurement of the linewidth of an ultrastable laser exciting a pair of 40Ca+ ions.