In an article published in Nature Communications*, the GPPMM group (XLIM Research Institute of CNRS and University of Limoges, France) in collaboration with Prof. Katori’s team from the University of Tokyo has successfully reached a major milestone towards the advent of highly compact optical clock. Optical clocks are presently very hot research topics as they outperform in precision the microwave atomic clock, and it is projected that an optical clock signal will set the new definition of the second as soon as the technology is sufficiently matured. Within the context of exploring new avenues to develop compact optical clocks, the researchers of the University of Tokyo and the CNRS/University of Limoges have confined, in a “chaplet fashion”, a chain of ultra-cold strontium atoms inside a micro-scaled hollow core of a specialty optical fibre called Kagome hollow-core photonic crystal fibre (HC-PCF). More remarkably, the confinement was achieved with no disruption from the inner wall of the hollow-core. It is this result that raised for the first time that compact optical clock is a realistic objective. Prof. Benabid (GPPMM group leader) said: “The impact of this result is three-fold. Firstly, we proved that we can micro-confine ultra-cold atoms without colliding them neither with the wall nor with themselves. Secondly, because of the fibre configuration we can assemble as many cold atoms as possible to increase the signal-to-noise ratio, which would be a huge leap in the performance of these clocks. Finally, this successful fibre based architecture could signal the path to compact optical clocks.”

*S. Okaba et al. Nature Communications 5, 4096 (2014), http://www.nature.com/ncomms/2014/140617/ncomms5096/abs/ncomms5096.html