# Rostock 2019 – wissenschaftliches Programm

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# Q: Fachverband Quantenoptik und Photonik

## Q 57: Poster: Quantum Optics and Photonics III

### Q 57.29: Poster

### Donnerstag, 14. März 2019, 16:15–18:15, S Fobau Physik

**Optimization of the cooling process in a mixed species ion Coulomb crystal** — •Leon Schomburg, Dimitri Kalincev, André P. Kulosa, and Tanja E. Mehlstäubler — PTB, Braunschweig, Germany

We report on laser cooling of multiple ions forming a so-called Coulomb crystal, which is confined in a linear rf Paul trap. In particular, we investigate the use of a mixed In^{+} - Yb^{+} crystal, where indium is used as a clock ion and is sympathetically cooled with ytterbium [1].

Increasing the number N of ions benefits clock spectroscopy as the averaging time decreases with 1/N, but it raises the challenge to maintain the control over systematic shifts of a single particle in ion chains. Our system supports excellent control over a crystal with tens of ions, reaching systematic clock uncertainties of 10^{−19} [1].

The efficiency of the cooling dynamics strongly depends on trap parameters and the crystal configuration. Similar results have been reported in [2]. Experimentally determined heating rates allow for the calculation of equilibrium temperatures, effective cooling rates and shifts for different configurations. We combine experimental data and theoretical simulation in order to find optimal configurations regarding cooling times and clock shifts. Interesting extensions of the theory include micromotion, as discussed in [3].

[1] J. Keller, arXiv:1803.08248v2 (2018), accepted for publication in Phys. Rev. A

[2] Tomasz P. Sakrejda and Boris B. Blinov, arXiv:1809.00240 (2018)

[3] H. Landa, arXiv:1809.10519 (2018)