Speaker
Description
In our cryogenic multi-Penning trap experiment, we aim to contribute to high-precision (anti-)proton $g$-factor$^{[1,2]}$ measurements pursued by the BASE collaboration, providing stringent tests of CPT symmetry$^{[3]}$. To reach precision at the parts-per-trillion level and to gain access to SME coefficients currently unreachable with existing techniques, we are implementing techniques based on quantum logic spectroscopy (QLS)$^{[4,5]}$, where both sympathetic cooling and spin-state detection of the (anti-)proton are mediated with a single $^{9}\mathrm{Be}^{+}$ ion. This will be achieved by coupling the particle motions via Coulomb interaction in a double-well potential.
In a previous experimental phase, we demonstrated several key QLS prerequisites in Penning traps, including optical sideband spectroscopy$^{[6]}$, ground-state cooling$^{[7]}$ of a single $^{9}\mathrm{Be}^{+}$, and fast adiabatic transport$^{[8]}$. In this contribution, we report on our current status, including the implementation of a new Penning trap stack. Within this setup, we aim to load protons, and achieve motional coupling between two $^{9}\mathrm{Be}^{+}$ ions in a symmetric double-well potential. This configuration serves as a proof-of-principle demonstration in which both particles are laser-accessible, before extending the scheme to the coupling of a $^{9}\mathrm{Be}^{+}$ ion to the (anti-)proton in an asymmetric double-well potential due to the 9:1 mass ratio of the particles.
Finally, we highlight recent developments for the future experimental phase, where we aim to sympathetically cool the (anti-)proton. We show simulations$^{[9]}$ describing the proposed cooling scheme, along with progress in the development of a microfabricated coupling trap where this cooling will be implemented. We also show that this cooling scheme could be applied to the vibrational spectroscopy molecular (anti-)hydrogen ions$^{[10]}$.
[1] G. Schneider et al., Science 358 (2017).
[2] C. Smorra et al., Nature 550 (2017).
[3] R. Lehnert, Symmetry 8 (2016).
[4] D. J. Heinzen and D. J. Wineland, Phys. Rev. A 42 (1990).
[5] P. O. Schmidt et al., Science 309 (2005).
[6] J. M. Cornejo et al., Phys. Rev. Res. 5 (2023).
[7] J. M. Cornejo et al., Phys. Rev. Res. 6 (2024).
[8] M. v. Boehn et al., Comms. Phys. 8 (2025).
[9] N. Poljakov et al., arXiv:2602.22826 (2026).
[10] S. Schiller et al., in review (2026).
| Academic level | PhD student |
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