Dresden 2026 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 50: German-French Focus Session: Superconducting Junctions and Quantum Circuits

TT 50.1: Topical Talk

Wednesday, March 11, 2026, 15:00–15:30, HSZ/0003

Josephson Quantum Tunneling at Odd Parity — Manuel Houzet¹, •Julia S. Meyer¹, and Yuli V. Nazarov² — ¹Univ. Grenoble Alpes, France — ²Delft University of Technology, The Netherlands

When a Josephson junction is embedded in an electromagnetic circuit, the superconducting phase difference across the junction becomes a quantum-fluctuating variable. The resulting quantum mechanics of the Josephson effect is the core ingredient for quantum technologies with superconducting circuits. On a microscopic level, the Josephson effect is related to Andreev bound states in the junction and depends on their occupation. When a single quasiparticle is trapped in an Andreev bound state--a situation known as quasiparticle poisoning--the junction is in the odd-parity sector. Because of parity conservation, such a poisoned state may exhibit a long lifetime. Our work opens a new avenue in this field by showing that the Josephson quantum mechanics in the odd-parity sector differs fundamentally from the conventional behavior in the even-parity sector. We uncover a rich phenomenology that contrasts with the naïve expectation of a simple supercurrent quench, which prevailed so far. Covering several representative cases, we predict a variety of novel effects that can be probed in upcoming experiments. Hybrid superconductor-semiconductor-superconductor junctions, that have been intensively studied in recent years both with nanowires and two-dimensional electron gases, provide a promising platform for observing these phenomena.

Keywords: Josephson junction; Andreev bound state; Quasiparticle poisoning