Mainz 2026 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 4: Quantum Computing and Simulation I

Q 4.2: Talk

Monday, March 2, 2026, 12:00–12:15, P 10

Tailoring spin–spin coupling of trapped ions by electrode shape optimization — •Kais Rejaibi, Patrick H. Huber, and Christof Wunderlich — Universität Siegen, Walter-Flex-Straße 3, 57072 Siegen

Trapped ions are a leading physical platform for quantum information processing. When scaling up such quantum processors, it is advantageous to control the qubit’s coherent dynamics by directly using electronic signals in the (quasi-)direct current (DC) and radio frequency (RF) regime, without conversion of these signals into the optical domain. N-qubit gates (N≥2) controlled by electronic signals are possible when applying a static or RF magnetic gradient field in a Paul trap. The matrix characterizing the interaction between N qubits can be tailored, for instance, by modifying the trapping potential confining the ions. We developed a numerical method to design and optimize electrode shapes that determine the trapping potential in 2D ion traps. From this we obtain the ion positions, mode structure, and effective interaction matrix. These results enter a cost function that measures how well a given design reproduces the desired interaction pattern under constraints such as maximum voltage and trap depth. By minimizing this cost function we obtain electrode geometries that favour the chosen interaction with low control-voltage requirements. While we focus on linear trap segments, the same approach can also be applied to more elements such as junctions in scalable ion-trap chips.

Keywords: Trapped ions; J-coupling matrix; Electrode shape optimization; Boundary element method