Dresden 2026 – scientific programme
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QI: Fachverband Quanteninformation
QI 11: Implementations IV
QI 11.3: Talk
Wednesday, March 11, 2026, 10:15–10:30, BEY/0245
Universal Pulses for Superconducting Qudit Ladder Gates — Boxi Li1,2, Francisco Cárdenas-López1, Andrian Lupascu3, and •Felix Motzoi1,2 — 1Forschungzentrum Jülich, Institute of Quantum Control — 2Universität zu Köln — 3University of Waterloo, Institute for Quantum Computing
In this work (PRX Quantum 6, 03035), we present a universal pulse construction for generating rapid, high-fidelity unitary rotations between adjacent qudit levels, thereby providing a prescription for any gate in SU(d). Control errors in these operations are effectively analyzed within a four-level subspace, including two leakage levels with approximately opposite detuning. By identifying the optimal degrees of freedom, we derive concise analytical pulse schemes that suppress multiple control errors and outperform existing methods. Remarkably, our approach achieves consistent coherent error scaling across all levels, approaching the quantum speed limit independently of parameter variations between levels. Numerical validation on transmon circuits demonstrates significant improvements in gate fidelity for various qudit sizes aiming for 10^-4 error. This method provides a scalable solution for improving qudit control and can be broadly applied to other quantum systems with ladder structures or operations involving multiple ancillary levels.
Keywords: Qudit; Decoherence; Universal pulses; Transmon; Leakage