Isolated Ion Clock: A New Approach

The exploitation of ions in confined isolation for the development of a new kind of portable atomic frequency standard was first proposed by Major in 1969; it was seen as an approach that promised extraordinary accuracy in a light, compact device suitable for aerospace applications (Major, 1969). Since then, with the advent of the laser, unimagined new technical frontiers opened up extending the field into the regime of optical frequency standards. The original concept of using resonant optical fluorescence to observe a microwave resonance in ions confined in a Paul trap, an approach of severely limited signal-to-noise ratio using the then available conventional lamps, quickly became an eminently fruitful approach when suitable lasers became available much later.