Microwave sensing of Andreev bound states in a gate-defined superconducting quantum point contact

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  • Vivek Chidambaram
  • Anders Kringhoj
  • Lucas Casparis
  • Kuemmeth, Ferdinand
  • Tiantian Wang
  • Candice Thomas
  • Sergei Gronin
  • Geoffrey C. Gardner
  • Zhengyi Cui
  • Chenlu Liu
  • Kristof Moors
  • Michael J. Manfra
  • Karl D. Petersson
  • Malcolm R. Connolly

We use a superconducting microresonator as a cavity to sense absorption of microwaves by a superconducting quantum point contact defined by surface gates over a proximitized two-dimensional electron gas. Renormalization of the cavity frequency with phase difference across the point contact is consistent with coupling to Andreev bound states. Near pi phase difference, we observe random fluctuations in absorption with gate voltage, related to quantum interference-induced modulations in the electron transmission. Close to pinch-off, we identify features consistent with the presence of a single Andreev bound state and describe the Andreev-cavity interaction using a Jaynes-Cummings model. By fitting the weak Andreev-cavity coupling, we extract similar to GHz decoherence consistent with charge noise and the transmission dispersion associated with a localized state.

Original languageEnglish
Article number023170
JournalPhysical Review Research
Issue number2
Number of pages9
Publication statusPublished - 31 May 2022

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