New J. Phys. 15, 053011 (2013)

Trapped ions are a potentially useful tool for applications in metrology and quantum information processing, but collecting their light emission in an efficient manner is a significant challenge. The use of high numerical-aperture optics is one possibility, but it limits the size and scalability of the system. The use of optical fibres to collect their light is hindered by the fact that the dielectric of the fibres can adversely affect the trapping potential applied to the ion. Hiroki Takahashi and co-workers from PRESTO in Japan and the University of Sussex in the UK have now managed to integrate a pair of optical fibres with a radiofrequency ion trap. To avoid disturbing the radiofrequency field around the ion, the researchers housed the fibres in two metallic concentric cylinders that not only shielded the fibres but also functioned as electrodes for an end-cap ion trap. This approach allowed the fibres to be located just 270 μm away from the ion, thus creating a compact and convenient means for capturing fluorescence. Such fibres not only allow the fluorescence to be easily analysed by photomultiplier tube detectors, but also allows the ion trap to serve as a fibre-coupled single-photon source.