Calcium Arrays in Penning Traps for Advanced Information processing with Nuclear Quanta

Objective

Recent progress in ion-trap quantum computing has been driven largely by quasi-2D RF trap architectures and ion–photon modules, which already enable high-fidelity gate operations and small-scale algorithms. However, scaling these systems to the fault-tolerant regime remains a key challenge due to increasing hardware overhead and control complexity. Penning traps, which employ strong magnetic fields to stabilize large ion arrays, offer a fundamentally different architecture that has so far been scarcely explored for quantum computation. In this regime, the strong magnetic field modifies the energy structure such that one no longer speaks of hyperfine qubits but rather of nuclear spin or electronic spin qubits. The nuclear spin states of 43Ca+ provide a rich multi-level manifold, enabling more information to be stored per ion and reducing the number of physical qubits required for large-scale processing. In this project, we aim to establish surface Penning traps as a competitive platform for quantum computing through three tightly connected objectives. The first objective is to identify and benchmark the nuclear spin qubit of 43Ca+ under high magnetic fields, providing the foundation for robust state preparation and measurement. The second objective is to explore the qudit manifold of the nuclear spin, implementing single- and two-qudit gates. The third objective is to demonstrate spin-cat states in this manifold, using them as intrinsically error-protected encodings and targeting the first experimental demonstration of error correction in a Penning trap device. All experiments will be carried out in a microfabricated surface Penning trap with individual trapping sites for each ion, enabling flexible geometries and scalability. Supported by close integration of theory, experiment, and industrial collaboration, the project will deliver the first robust multi-level quantum processing in a Penning trap and reinforce Europe’s position in quantum technologies.