The 87-Sr optical frequency standard at PTB

TL;DR

This paper reports a highly precise optical frequency standard based on 87-Sr atoms in an optical lattice, achieving a fractional uncertainty of 1.5×10^-16, supporting its role as a secondary standard of the second.

Contribution

The paper presents a new measurement of the 87-Sr optical clock transition frequency with unprecedented precision and confirms its consistency with previous measurements.

Findings

Measured transition frequency: 429 228 004 229 872.9(5) Hz

Fractional uncertainty of 1.5×10^-16

Supports the transition as a reliable secondary standard

Abstract

With 87-Sr atoms confined in a one dimensional optical lattice, the frequency of the optical clock transition 5s^2 ^1S_0 - 5s5p ^3P_0 has been determined to be 429 228 004 229 872.9(5) Hz. The transition frequency was measured with the help of a fs-frequency comb against one of PTB's H-masers whose frequency was measured simultaneously by the PTB Cs fountain clock CSF1. The Sr optical frequency standard contributes with a fractional uncertainty of 1.5 10^-16 to the total uncertainty. The agreement of the measured transition frequency with previous measurements at other institutes supports the status of this transition as secondary representation of the second with the currently smallest uncertainty.