Robust artificial clock transition by continuous dynamical decoupling in multi-ion calcium crystals

authored by
Lennart Pelzer

Optical atomic clocks reach astonishingly low frequency uncertainties. Therefore, they are a valuable tool for applications even beside time determination. Predicted extensions of the standard model of particle physics can be tested using these clocks. For this reason, they can help to uncover unresolved discrepancies between these models and the observed universe. A low frequency uncertainty also enables height measurements according to general relativity. Clock comparisons over long distances might be used to refine geodetic models of the earth’s gravitational potential. A variety of atomic species and techniques are in competition for realizing the most accurate clock. The aluminium single ion clock is, at the moment, the most accurate clock. But it is impeded by long averaging times due to the quantum projection noise limit. For some of the aforementioned applications, this is a serious drawback. Larger ion crystals offer an increased signal-to-noise ratio, but maintaining their frequency accuracy is demanding, as the strong confinement potentials shift the atomic resonance. This thesis reports on the experimental realization of a continuous dynamical decoupling technique. Designed coupling of Zeeman sub-levels by radio-frequency fields is used to mitigate major frequency shifts in 40Ca+ crystals. The obtained artificial clock transition has the potential to compete with more promising clock transitions of different atomic species regarding its low sensitivity to magnetic field fluctuations as well as suppressed quadrupole and tensorial ac-Stark shifts. Long coherence times in multi-ion 40Ca+ crystals are obtained for the artificial transition. Thus, the system’s potential for a low statistical uncertainty makes it promising as a replacement for a lattice clock in a compound clock or for applications where frequency differences must be determined on a short timescale.

QUEST-Leibniz Research School
Doctoral thesis
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