The "Quantum Sensors with Cold Ions" group is one of the 7 independent Junior Research Groups of QUEST. The group investigates the potential of ultra-stable optical clocks and frequency standards with improved short term stability based on laser cooled ions for applications in navigation and geodesy.

Novel ion-trap chips with integrated electronic circuits are being developed, that will allow to scale up the number of ions in micro-structured and segmented traps. In such arrays of up to 100 trapped and laser cooled ions a fractional frequency resolution of up to 10^-18 can be achieved with a significantly reduced integration time. This would allow to probe local gravitational fields in a differential frequency measurement due to the relativistic red-shift with a height resolution of only 1 cm. With such a sensor geodetic measurements of the geoid can be performed as well as tests of general relativity.

For the ultra-precise trap structures we develop laser cutting and sputtering techniques with µm tolerances and well defined surface roughness.  In these chip traps coulomb crystals of indium and ytterbium ions are then cooled and investigated spectroscopically at temperatures below 1mK.