Measuring absolute frequencies beyond the GPS limit via long-haul optical frequency dissemination

TL;DR

This paper demonstrates surpassing GPS frequency dissemination limits by using a long optical fiber link to a remote atomic clock, enabling high-precision measurements without local atomic clocks and significantly improving frequency accuracy.

Contribution

It introduces a fiber-optic link method to achieve high-precision frequency dissemination beyond GPS limits without local atomic clocks, and reports a two-order magnitude improvement in transition frequency accuracy.

Findings

Successfully addressed the $^1$S$_0$---$^3$P$_0$ transition in ultracold $^{173}$Yb.

Achieved frequency measurement precision exceeding GPS-based methods.

Improved the accuracy of the transition frequency by two orders of magnitude.

Abstract

Global Positioning System (GPS) dissemination of frequency standards is ubiquitous at present, providing the most widespread time and frequency reference for the majority of industrial and research applications worldwide. On the other hand, the ultimate limits of the GPS presently curb further advances in high-precision, scientific and industrial applications relying on this dissemination scheme. Here, we demonstrate that these limits can be reliably overcome even in laboratories without a local atomic clock by replacing the GPS with a 642-km-long optical fiber link to a remote primary caesium frequency standard. Through this configuration we stably address the $^1$S$_0$---$^3$P$_0$ clock transition in an ultracold gas of $^{173}$Yb, with a precision that exceeds the possibilities of a GPS-based measurement, dismissing the need for a local clock infrastructure to perform high-precision tasks beyond GPS limit. We also report an improvement of two orders of magnitude in the accuracy on the transition frequency reported in literature.