Impact of Andreev Bound States within the Leads of a Quantum Dot Josephson Junction

Abstract

Detection and control of Andreev bound states (ABSs) localized at semiconductor-superconductor interfaces are essential for their use in quantum applications. Here we investigate the impact of ABSs on the supercurrent through a Josephson junction containing a quantum dot (QD). Additional normal-metal tunneling probes on both sides of the junction unveil the ABSs residing at the semiconductor-superconductor interfaces. Such knowledge provides an ingredient missing in previous studies, improving the connection between theory and experimental data. By varying the ABS energies using electrostatic gates, we show control of the switching current, with the ability to alter it by more than an order of magnitude. Finally, the large degree of ABS tunability allows us to realize a three-site Andreev molecule in which the central QD is screened by both ABSs. This system is studied simultaneously using both supercurrent and spectroscopy. Published by the American Physical Society 2025