Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 40: Superconductivity: Qubits 1

TT 40.4: Vortrag

Mittwoch, 3. April 2019, 10:15–10:30, H48

Resolving the Positions of Parasitic Defects in Superconducting Qubits — •Alexander Bilmes¹, Anthony Megrant², Julian Kelly², Rami Barends², John M. Martinis², Weiß Georg¹, Alexey V. Ustinov^1,3, and Jürgen Lisenfeld¹ — ¹Karlsruhe Institute of Technology, 76137 Karlsruhe, Germany — ²Google Inc., Santa Barbara, USA — ³Russian Quantum Center, National University of Science and Technology MISIS, Moscow 119049, Russia

We demonstrate a new technique to identify the spatial positions of decoherence-inducing material defects known as Two-Level-Tunneling systems (TLS) in superconducting qubits. For this, we operate a transmon qubit circuit in a DC-electric field that is generated by several electrodes surrounding the sample chip, and study the TLS response by monitoring their resonance frequencies using qubit swap spectroscopy. By comparing measured and simulated coupling strengths of TLS to each DC-electrode, we obtain information about the possible locations and hosting interfaces of observed surface TLS. This method is applicable to any ready-made transmon qubit, and opens a path for the optimization and verification of qubit fabrication procedures by directly indicating which circuit interfaces must be improved in order to enhance qubit coherence.