Freiburg 2019 – scientific programme

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FM: Fall Meeting

FM 73: Quantum Sensing: Applications & Spectroscopy

FM 73.3: Talk

Thursday, September 26, 2019, 14:30–14:45, Aula

Resolving the positions of defects in superconducting quantum bits — •Alexander Bilmes¹, Anthony Megrant², Paul Klimov², Julian Kelly², Rami Barends², John M. Martinis², Gerog Weiss¹, Alexey V. Ustinov^1,3, and Juergen Lisenfeld¹ — ¹Physikalisches Institut, Karlsruhe Institute of Technology, 76131 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 defect's location and the circuit interface at which it resides. This provides a viable tool applicable to various qubit types, which enables one to optimize qubit fabrication procedures by directly indicating which circuit interfaces must be improved in order to enhance qubit coherence.