Berlin 2024 – scientific programme

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QI: Fachverband Quanteninformation

QI 19: Superconducting Electronics: Qubits I (joint session TT/QI)

QI 19.5: Talk

Wednesday, March 20, 2024, 16:00–16:15, H 0104

Mapping the lateral positions of individual material defects in superconducting transmon qubits — •Alexander K. Händel, Alexey V. Ustinov, and Jürgen Lisenfeld — Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany

Material defects are limiting the coherence of superconducting circuits and mitigating their effects is vital in the realization of functional quantum devices. With transmon qubits, the spatial distribution of most coherence breaking defects is likely to be inhomogeneous, due to the qubit's electric field strength varying greatly with position, affecting a defects participation ratio. By tuning the resonance frequency of individual defects with static electric fields induced by on-chip electrodes we are able to resolve their positions on the qubit chip. We present first results of mapping the positions of defects in a transmon qubit, distinguishing defects on the qubit capacitor from those residing on the leads of Josephson junctions. Our results identify critical circuit components which contain major defects detrimental for the qubit performance and provide valuable information to improve qubit design and fabrication methods.