Developing the systems needed to improve the measurement of the SI second.
Precise measurement of time are essential in many areas including international time distribution, telecommunications, global positioning satellite systems and high-speed banking. Since 1967 the SI second has been defined by the energy transitions or ‘oscillations’ occurring in Caesium133 ‘atomic clocks’. Optical clocks now exist, where atoms or ions are ‘trapped’ by lasers, that have a measurement uncertainty two orders of magnitude lower than the best Caesium clock. However, no leading candidate for a new primary standard for time has been identified. Combining two or more optical clocks into a ‘composite clock’ would allow each to calibrate the other in the system but this poses special experimental challenges. Techniques such as quantum-logic spectroscopy, that removes the requirements for such things as efficient cooling, are needed to explore the potentials of these systems.
This project will develop techniques that enable composite clocks, or different clock types, to stabilise one common oscillator, including optimising signal links and real-time data processing. Systems that are distributed over two or more different locations will be examined; and the accuracy of single-species atomic clocks will be improved by the establishment of reference transitions in composite clocks. Two-species composite systems will be investigated to enable clock operation with currently inaccessible atomic systems such as highly charged ions.
Project outputs will benefit all sectors relying on precise time measurements and input into the selection of suitable reference systems for a redefinition of the SI second, an essential contribution to fundamental metrology and to the long-term development of the SI system of units.