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TT: Fachverband Tiefe Temperaturen

TT 16: Poster Session Superconductivity, Cryogenic Particle Detectors, Cryotechnique

TT 16.39: Poster

Montag, 16. März 2020, 15:00–19:00, P2/EG

Two-level-systems spectroscopy in Transmon qubits. — •Serhii Volosheniuk¹, Alexander Bilmes¹, Alexey V. Ustinov^1,2, and Jürgen Lisenfeld¹ — ¹Physikalisches Institut, Karlsruhe Institute of Technology, Karlsruhe 76131, Germany — ²Russian Quantum Center, National University of science and Technology MISIS, Moscow 1190449, Russia

Despite the announcement of achieving quantum supremacy, we are still far away from a superconducting quantum processor. One of the principal causes is low qubit fidelity due to parasitic material defects. These act like two-level-systems (TLS) which limit qubit coherence and create environmental fluctuations.

To understand how TLS are forming during sample fabrication, we seek information on their location in a given qubit circuit. For this, TLS are tuned with applied elastic strain and dc electric fields, allowing us to distinguish defects in Josephson junction tunnel barriers from those at film interfaces[1,2].

Here we present our latest results and ideas on TLS spectroscopy with E-field tuning in qubits. One goal is to obtain two-dimensional maps of defect locations in the vicinity of the qubits Josephson junctions to elucidate and mitigate the role of junction lithography on defect formation.

[1] J. Lisenfeld et al., npj Quantum Inf 5, 105 (2019)

[2] A. Bilmes et al., arXiv:1911.08246 (2019)