The implementation of Global Navigation Satellite Systems (GNSS) increases the performance requirements in smaller clocks. In addition to past works in the field of optically pumped caesium beam compact clocks (Cs4), SYRTE designs and develops two kinds of clocks within the previous frame:

 CPT, for Coherent Population Trapping. The pulsed CPT interrogation technique (SYRTE) is patented. This innovating method gives a high performance even with thermal atoms. It is currently implemented at ambient temperature with a cell containing caesium vapour and buffer gases. The use of laser cooling will make it possible to suppress the buffer gases and consequently to improve the frequency accuracy and the long term stability, which are currently limited by the thermal sensitivity due to the collisions between the buffer gases and the caesium vapour.

 HORACE for HOrloge à Refroidissement d’Atomes en CEllule (Clock with atom cooling in a cell), based on isotropic cooling. The atomic preparation, the Ramsey interrogation and the atomic detection are realized at the same place by means of an appropriate sequence. The expected performances are about 10-14 for accuracy and a few 10-13 at 1s for frequency stability, which are at least ten times better than for current atomic clocks of similar dimensions.