High-accuracy ion-based optical clocks

The SI second is currently defined as the transition between the two hyperfine levels of the ground state of the caesium-133 atom. These atomic clocks are accurate to around 10^-15 and provide essential time and frequency services in a wide range of areas including electricity grids, finance, telecommunications, global positioning and the internet. Recently, optical clocks based on single trapped ions have been developed that display accuracy below 10^-18, raising the possibility of their use to redefine the SI second. However, these clocks currently require weeks of averaging time to reduce measurement uncertainty. Optical clocks using multiple ions or ions with higher frequencies could improve this situation but require developing and testing before use as primary standards of time and frequency.

Building on the work of EURAMET projects CC4C, TSCAC and TOCK  this project will develop multi-ion optical clocks with four or more ions. This will include the production of new methodologies for trapping and cooling large ensembles of ions using ion-traps and ion confinement in engineered static electric and optical fields. These are anticipated to improve performance by at least a factor of two over single ion clocks, which will be verified via intercomparisons To compliment this thorium-229 and Hydrogen Chloride based clocks, which show minimal sensitivity to external perturbation, will also be investigated. As well as providing a basis for a redefinition of the SI second – which will benefit all industries dependent on accurate timing - the project outputs will also contribute to improvements in fields such as quantum computing and quantum information processing.