Science case
Trapped ions in Rydberg states come with strong dipolar interactions and a high polarizability, which can be used to explore many-body effects. By utilizing a cryogenic Penning trap, longer observation times can be achieved and with a higher scalability (Penning systems are naturally 2D, whereas Paul systems are 1D). As part of the OPEN-2QS collaboration, our group at Mainz will design, construct, and operate a quantum simulator to take advantage of all these features. This Rydberg-excited 40Ca-ion cryogenic Penning trap quantum simulator will consist of 3D trap electrodes fabricated in-house using SLE, a custom-built 1.5T permanent Halbach magnet, and 2-photon Rydberg excitation scheme with deep UV lasers. This challenging yet novel combination of technologies will result in a platform sensitive to interesting new physics, such as quantum glasses, exploring non-equilibrium phenomena, etc. For more details, see our first paper (PRX2026) on the physics reach. We are looking for Master/PhD/postdocs who are excited to take up the challenge. Please contact Prof. Ferdinand Schmidt-Kaler for details! Currently we're in the design/construction phase, so hardware skillsets are particularly desired.
Previous research focussed on developing 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). We reported the first excitation of trapped ions to their Rydberg states (see PRL2015 and PRL2021). By laser coupling to Rydberg states, the polarizability 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).
Collaborations
The OPEN-2QS project is a collaboration with the groups of Igor Lesanovsky (Tübingen) and Marcus Hennrich (Stockholm).
We have also had fruitful collaborations with many other research groups:
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- ERyQSenS and QuantERA: projects on Entangled Rydberg matter for quantum sensing and simulations, with Marcus Hennrich (Stockholm) , Nikolay V. Vitanov (Bulgaria) , Jean Michel Raimond (Paris), Michel 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).
- Peter Zoller (Innsbruck)
Funding Organizations
Research for OPEN-2QS is funded by an ERC Synergy Grant 2025.
Additional funding has come from: the EU's Horizon 2020 research and innovation programme under grant agreement No. 640378 (RYSC); Marie-Skłodowska-Curie grant agreement No. 796866 (Rydion); DFG SPP 1929 “Giant interactions in Rydberg Systems” (GiRyd); and the EU-co funded program through ERA-Net QuantERA for the project ERyQSenS. 
Team members
Dr. Larisa Thorne
Dr. Guillaume Coeuret Cauquil
Om Pote
Prof. Dr. Ferdinand Schmidt-Kaler
Past:
Santiago Bogino
Dr. Han Bao
Open positions
We offer Bachelor, Master, PhD, and postdoc projects! Work focuses on new aspects of Rydberg physics, including 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.
Please send your application including a brief motivation statement and CV electronically to Prof. Ferdinand Schmidt-Kaler