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TT: Fachverband Tiefe Temperaturen

TT 18: Superconductivity: Poster

TT 18.43: Poster

Montag, 18. März 2024, 15:00–18:00, Poster C

Quantum Coherence of Josephson Vortices in High Impedance Long Junctions — •Julian Feiler¹, Micha Wildermuth¹, Jan Nicolas Voss¹, Maximilian Kristen^1,2, Mikhail V. Fistul³, Hannes Rotzinger^1,2, and Alexey V. Ustinov^1,2 — ¹Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany — ²Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany — ³Theoretische Physik III, Ruhr-Universität Bochum, 44801 Bochum, Germany

The physics of Josephson vortices in long junctions spans from nonlinear soliton dynamics with relativistic effects to the interesting applications of coherent microwave generation. In the majority of the past experiments, the vortices are modelled as classical particles and only a small subset showed signatures of a quantum behaviour. The main reason originates in the low impedance electromagnetic environment of the vortices which was set by the geometry of the electrodes. With the advent of high kinetic inductance electrode materials, such as granular aluminium, this constraint is relaxed and Josephson vortices behaving as quantum particles are now within reach.

In the presented experiment, we employ a coupled long Josephson junction-resonator system and characterise it at milli-Kelvin temperatures. We show spectroscopic data with magnetic fields applied in-plane and, to tune out residual z-components, also perpendicular to the plane of the junction. We observe indications of quantum two-level systems and present associated coherence and relaxation times.

Keywords: Long Josephson junction; Josephson vortex