Towards a squeezing-enhanced atomic clock on a chip
Konstantin Ott (LKB)

This thesis describes the conception and construction of an “entanglement-enhanced”
trapped atom clock on an atom chip (TACC). The key feature of this new experiment
is the integration of two optical Fabry-Pérot micro resonators which enable generation
of spin-squeezed states of the atomic ensemble via atom-light interactions and non-
destructive detection of the atomic state.
It has been shown before that spin-squeezed states can enhance the metrological
performance of atomic clocks, but existing proof-of-principle experiments have not yet
reached a metrologically relevant level of precision. This is the first goal of the new
To retain the compactness and stability of our setup, we chose the optical resonator
to be a fiber Fabry-Pérot (FFP) resonator where the resonator mirrors are realized on
the tip of optical fibers. To meet the requirements of our experiment, a new generation
of FFP resonators was developed in the context of this thesis, demonstrating the longest
FFP resonators to date. For this purpose, we developed a “dot milling” procedure using
a focused CO2-laser that allows shaping of fused silica surfaces with unprecedented
precision and versatility. Beyond the TACC experiment these long FFP resonators
open up new applications in other fields as in the ion trapping community or for
frequency filtering.
Incorporating optical resonators in the TACC system necessitates a new atom chip
design, allowing transportation of the atom cloud into the resonator. We present the
design and the fabrication of this atom chip.
The completed setup will enable investigations of the interplay of spin-dynamics in
presence of light mediated correlations and spin-squeezing at a metrologically relevant
stability level of 10^(−13) at 1 s.