Cold, trapped ions excited to Rydberg states

Science case

We develop methods for the application of trapped Rydberg ions in quantum information processing experiments (see review paper). Trapped Rydberg ions feature several important properties that are unique in their combination: Ions in a Paul trap are tightly bound in a harmonic potential, in which their internal and external degrees of freedom can be controlled in a precise fashion (see here). High fidelity state preparation of both internal and motional states of the ions has been demonstrated, and the internal states have been employed to store and manipulate qubit information, see our Quantum Computing project.

But additionally to regular trapped ions, Rydberg states come with strong dipolar interactions, a high polarizability and all this may be used to explore many-body effects. We reported the first excitation of trapped ions to their Rydberg states (see PRL2015 and PRL2021). By laser coupling to Rydberg states, the polarisability of the ions can be both enhanced and tuned (see NJP 2023) for plaquette interactions (NJP2015). Excitation to Rydberg state may present an attractive alternative for fast entangling operations for a future quantum computer or a quantum simulator (see PRL2019).


We have fruitful collaborations with the research groups of

Peter Zoller, Innsbruck, Igor Lesanovsky, Tübingen, Marcus Hennrich, Stockholm

ERyQSenS, QuantERA project on Entangled Rydberg matter for quantum sensing and simulations, in collaboration with Marcus Hennrich, Stockholm , Nikolay V. Vitanov, Bulgaria , Jean Michel Raimond, ParisMichel Brune, Paris , Igor Lesanovsky, Tübingen/Nottingham  and Weibin Li, Nottingham .

Giant interactions in Rydberg Systems (GiRyd) network with Tilman Pfau, Stuttgart and Jan M. Rost, Dresden.

Funding Organisations

This research has received funding from the EU's Horizon 2020 research and innovation programme under grant agreement No. 640378 (RYSC) and is funded by Marie-Skłodowska-Curie grant agreement No. 796866 (Rydion).

Additional funding has come from DFG SPP 1929 “Giant interactions in Rydberg Systems” (GiRyd), and the EU-co funded programme through ERA-Net QuantERA for the project ERyQSenS.


Alexander Schulze-Makuch
Dr. Han Bao
Dr. Jonas Vogel
Prof. Ferdinand Schmidt-Kaler

Open positions

We offer BAC, Master, PhD, Postdoc projects in the project! Work focuses on new aspects of Rydberg physics, entanglement operations, possibly setting up a cryogenic trap for enhanced lifetimes. This offers unique opportunities for doing experiments with trapped ions and gaining visibility in high rank collaborations. Requests for further information and applications can be directly sent via email to Prof. Schmidt-Kaler.