Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 40: Superconductivity: Qubits 1

TT 40.3: Vortrag

Mittwoch, 3. April 2019, 10:00–10:15, H48

Tuning decoherence sources in Transmon qubits by electric fields — •Jürgen Lisenfeld¹, Alexander Bilmes¹, Georg Weiss¹, Rami Barends², Anthony Megrant², Julian Kelly², John M. Martinis², and Alexey V. Ustinov^1,3 — ¹Physikalisches Institut, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany — ²Google Inc., Santa Barbara — ³Russian Quantum Center, National University of Science and Technology MISIS, Moscow 119049, Russia

A major part of decoherence in superconducting quantum bits arises from their interaction with microscopic material defects forming parasitic two-state quantum systems, so-called TLS. For the further advancement of quantum processors, it is thus vital to gain a better understanding of TLS properties and how they are formed.

Here we demonstrate a new technique to tune the resonance frequencies of defects by exposing a transmon qubit circuit to a DC-electric field generated by electrodes surrounding the sample chip.

Our experiments indicate that about 50% of over 200 individually observed TLS are tuned by the electric field, as it is expected from defects residing on qubit circuit electrodes or at substrate interfaces. In comparison, practically all TLS respond to mechanical strain that is generated by a piezo actuator. Our statistical analyses of the defect's coupling strengths to the qubit, strain, and electric field reveal two distinguishable defect classes whose probable origins will be discussed.