Stability of a trapped atom clock on a chip

TL;DR

This paper demonstrates a compact, chip-based atomic clock using ultracold rubidium atoms with long coherence times, achieving high stability and detailed noise analysis, paving the way for improved portable timekeeping devices.

Contribution

It introduces a stable, chip-integrated atomic clock with long coherence times and detailed noise characterization, advancing portable atomic clock technology.

Findings

Achieved fractional frequency stability of 5.8×10⁻¹³ at 1 second

Long coherence times enabled high contrast Ramsey interrogation

Identified key noise sources including atom temperature and magnetic field fluctuations

Abstract

We present a compact atomic clock interrogating ultracold 87Rb magnetically trapped on an atom chip. Very long coherence times sustained by spin self-rephasing allow us to interrogate the atomic transition with 85% contrast at 5 s Ramsey time. The clock exhibits a fractional frequency stability of $5.8\times 10^{-13}$ at 1 s and is likely to integrate into the $1\times10^{-15}$ range in less than a day. A detailed analysis of 7 noise sources explains the measured frequency stability. Fluctuations in the atom temperature (0.4 nK shot-to-shot) and in the offset magnetic field ($5\times10^{-6}$ relative fluctuations shot-to-shot) are the main noise sources together with the local oscillator, which is degraded by the 30% duty cycle. The analysis suggests technical improvements to be implemented in a future second generation set-up. The results demonstrate the remarkable degree of technical control that can be reached in an atom chip experiment.