Atomic Coherence of 2 minutes and Instability of 1.5E-18 at 1 s in a Wannier-Stark Lattice Clock

TL;DR

This paper investigates atomic coherence limits in a 87Sr optical lattice clock, achieving a coherence time of over 118 seconds and demonstrating an instability of 1.5E-18 at 1 second, advancing precision timekeeping.

Contribution

It provides a detailed analysis of decoherence mechanisms and demonstrates near-fundamental limit coherence times in a lattice clock, enhancing clock stability.

Findings

Achieved a 118-second atomic coherence time at reduced density.

Measured a clock instability of 1.5E-18 at 1 second.

Identified key decoherence mechanisms affecting atomic coherence.

Abstract

We explore the limits of atomic coherence and measurement precision in a 87Sr optical lattice clock. We perform a detailed characterization of key effects, including lattice Raman scattering and atomic collisions in a shallow lattice configuration, determining a 174(28) s 3P0 clock state lifetime. Investigation of atomic coherence across a range of lattice depths and atomic densities reveals decoherence mechanisms related to photon scattering and atomic interaction. At a reduced density, we observe a coherence time of 118(9) s, approaching the fundamental limit set by spontaneous emission. Guided by this coherence understanding, we demonstrate a clock instability of 1.5E-18 at 1 s in fractional frequency units. Our results are important for further advancing the state-of-the-art of an optical lattice clock for fundamental physics applications.