Regensburg 2022 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 27: Quantum Coherence and Quantum Information Systems (joint session TT/DY)

TT 27.6: Talk

Thursday, September 8, 2022, 10:45–11:00, H22

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

In superconducting quantum bits, material defects at the surface of circuit electrodes and the substrate constitute a major source of decoherence. In our experiment, we detect individual defects with a transmon qubit while tuning their resonance frequencies with applied static electric fields. We fabricated samples that feature on-chip gate electrodes that are placed close to the qubit island. By measuring the coupling strength of each detected defect to various electrodes, we are able to deduce the defect's position on the qubit chip. Our goal is to create two-dimensional maps of defect distribution over qubit electrodes. This will help to identify circuit components which contain majority of coherence-breaking defects and improve fabrication methods towards more coherent qubits.