PTB is the national institute for science and technology and the highest technical authority of the Federal Republic of Germany for the field of metrology and certain sectors of safety engineering. PTB comes under the auspices of the Federal Ministry of Economics and Technology. A fundamental task of PTB is to realize and maintain the legal units in compliance with the International System of Units (SI) and to disseminate them, above all within the framework of legal and industrial metrology.

The realization of time and frequency is among the most prominent activities of PTB. For nearly 50 years PTB has developed and operated primary cesium clocks and has contributed to the realisation of international atomic time TAI. PTB has long-standing experience in operating an Yb+ single-ion clock. PTB’s Time and Frequency Department presently operates two primary Cs fountain clocks and femtosecond frequency combs for absolute frequency and frequency ratio measurements.

At PTB in Brauschweig an ion trapping experiment for Th+ has been set up, including several tunable laser sources for resonance lines of Th+ and for two-photon excitation of the isomeric state. The laboratory is integrated into the infrastructure of the time and frequency department, including optical and microwave frequency standards. Staff includes experienced technicians and workshops for electronics, optics, mechanical and vacuum systems.