Clemens Winkelmann (Grenoble): Dissipation and friction in superconducting Josephson junctions

Physikalisches Kolloquium

The currently most advanced realizations of quantum information processors are based on superconducting circuits, which have Josephson junctions as their central electronic elements. Josephson junctions can be quantum coherent, that is, dissipation free. However, in the presence of noise or a strong drive, the quantum dynamics of the phase can become irreversible. I will present two experiments investigating irreversibility in the phase dynamics in Josephson junctions, in the two opposite limits of large and low internal friction, respectively. In the first experiment, we detect in real time the heat dissipated by individual 2π slips of the phase, which allows quantifying the major role played by thermal effects in quantum circuits [1]. In the second experiment, we investigate a Josephson junction across a single magnetic atom. We show that the electron-hole asymmetric density of states inside the function leads to a non-reciprocal friction. This manifests as an asymmetry in the retrapping currents, that is, a Josephson diode effect [2].

[1] Calorimetry of a phase slip in a Josephson junction, E. Gümüs et al., Nat. Phys. 19, 196 (2023).

[2] Diode effect in Josephson junctions with a single magnetic atom, M. Trahms et al., Nature 615, 628 (2023).

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