Regensburg 2025 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 50: Superconducting Electronics: SQUIDs, Qubits, Circuit QED II

TT 50.6: Talk

Thursday, March 20, 2025, 16:15–16:30, H36

Resonant escape in Josephson tunnel junctions under millimeter-wave irradiation — •Jonas N. Kämmerer¹, Sergei Masis¹, Karo Hambardzumyan¹, Philipp Lenhard¹, Urs Strobel¹, Jürgen Lisenfeld¹, Hannes Rotzinger^1,2, and Alexey V. Ustinov^1,2 — ¹Physikalisches Institut (PHI), Karlsruher Institut für Technologie, 76131 Karlsruhe, Germany — ²Institut für QuantenMaterialien und Technologien (IQMT), Karlsruher Institut für Technologie, 76131 Karlsruhe, Germany

Operating superconducting quantum circuits at mm-wave frequencies around 100 GHz promises several advantages. For example, it may allow for much higher operating temperatures above 1 K and faster qubit manipulation. We study the microwave-driven dynamics of a superconducting phase qubit made of Nb/AlO_x/Nb junction. In particular, we have measured the switching current distributions at radiation frequencies above 100 GHz and observed clear double-peak structures. The data indicate a resonant escape of the phase as well as an irradiation-induced suppression of the potential barrier. This behavior is well described by the strong-driving model of the resonant escape[1]. While being measured in the quasi-classical regime of thermally activated escape, our results point towards a feasibility of operating phase qubits at mm-wave frequencies.

[1] M.V.Fistul,A.Wallraff,A.V.Ustinov, Phys.Rev.B68, 060504 (2003).

Keywords: mm-wave; switching current; resonant phase escape; Circuit QED