Absolute frequency measurement of a Yb optical clock at the limit of the Cs fountain

• DOI: 10.48550/arxiv.2212.14242
• Publication Date: 2023-05-03
• Authors: Irene Goti; Stefano Condio; Cecilia Clivati; Matias Risaro; Michele Gozzelino; Giovanni A Costanzo; Filippo Levi; Davide Calonico; Marco Pizzocaro
• Keywords: Atomic Physics (physics.atom-ph); 0103 physical sciences; FOS: Physical sciences; Frequency metrology; optical lattice clock; Cs fountain; SI second; frequency metrology; optical lattice clock; Cs fountain; SI second; 01 natural sciences; Physics - Atomic Physics

Abstract We present the new absolute frequency measurement of ytterbium (171Yb) obtained at INRiM with the optical lattice clock IT-Yb1 against the cryogenic caesium (133Cs) fountain IT-CsF2, evaluated through a measurement campaign that lasted 14 months. Measurements are performed by either using a hydrogen maser as a transfer oscillator or by synthesizing a low-noise microwave for Cs interrogation using an optical frequency comb. The frequency of the 171Yb unperturbed clock transition 1 S 0 → 3 P0 results to be 518 295 836 590 863.44(14) Hz, with a total fractional uncertainty of 2.7 × 10 − 16 that is limited by the uncertainty of IT-CsF2. Our measurement is in agreement with the Yb frequency recommended by the Consultative Committee for Time and Frequency. This result confirms the reliability of Yb as a secondary representation of the second and is relevant to the process of redefining the second in the International System of Units on an optical transition.