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arXiv · 2102.05206

Microwave Sensing of Andreev Bound States in a Gate-Defined Superconducting Quantum Point Contact

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

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 adiabatic 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. We identify features consistent with the presence of single Andreev bound states and describe the Andreev-cavity interaction using a dispersive Jaynes-Cummings model. By fitting the weak Andreev-cavity coupling, we extract ~GHz decoherence consistent with charge noise and the transmission dispersion associated with a localized state.

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Vivek Chidambaram, Anders Kringhøj, Lucas Casparis, Ferdinand Kuemmeth, Tiantian Wang, Candice Thomas, Sergei Gronin, Geoffrey C. Gardner, Zhengyi Cui, Chenlu Liu, Kristof Moors, Michael J. Manfra, Karl D. Petersson, Malcolm R. Connolly. 2021-02-10. Microwave Sensing of Andreev Bound States in a Gate-Defined Superconducting Quantum Point Contact. https://doi.org/10.1103/physrevresearch.4.023170

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