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Precise timing is vital in many sectors – an EMPIR project on optical clocks has made lasting ties between industry and metrology institutes

Since 1968 the SI second is defined upon caesium hyperfine transition and caesium atomic clocks have been the backbone of the Coordinated Universal Time (UTC).

Advances in fields which rely upon accurate timekeeping, such as telecommunications, satellite navigation, and fundamental physics have placed an increasing need for more accurate realisations of the second.

Optical clocks, based upon atoms such as ytterbium (Yb) and strontium (Sr) or ions such as Al+, Yb+, Sr+ offer the potential to be up to 2 orders of magnitude more accurate in comparison to the best caesium clocks.

However, to fully exploit optical clocks potential it is necessary to overcome some barriers including improving the stability of the laser frequency, which is affected by thermal noise from the mirror coatings of the reference cavity, and overcoming the ‘quantum projection noise’. An innovative technique to overcome the laser noise limitation was successfully addressed by the German National Metrology Institute PTB in the EMPIR project Ultra-stable optical oscillators from quantum coherent and entangled systems (17FUN03, USOQS).

This project implemented, studied and characterised both established and brand-new methods for the development of optical clocks and was based upon work in a previous EMRP project QESOCAS.

After completion of the USOQS project in 2022, members of the consortium and industrial stakeholders continued collaboration in two new European Commission Horizon 2020 projects: Project HORIZON-CL4-2021-DIGITAL-EMERGING-02-20 AQuRA and H2020-MSCA-ITN-2019 MoSaiQC.

The AQuRA is an industry-led project which aims to deliver the world’s first industry-built, rugged, transportable optical clock and demonstrate its usefulness in applications including telecommunications, geodesy and metrology.

The MoSaiQC project will train 15 early-stage researchers in innovative quantum, atomic clock technology, with training covering all aspects of technology, from theory to the development of innovative systems to applications in industrial sectors.

The coordinator of this highly success full project, Filippo Levi, from INRiM, commented on this:

“Within the USOQS project we tested different innovative avenues to improve optical clocks. Some of them were indeed successfully. Finding the way to overcome a fundamental limit is always a big challenge and a great scientific satisfaction.”

This EMPIR project is co-funded by the European Union's Horizon 2020 research and innovation programme and the EMPIR Participating States

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