Quartet tomography in multiterminal Josephson junctions

The authors propose here how to detect quartets in hybrid multiterminal Josephson junctions from the analysis of the current-phase relation and Andreev bound state (ABS) spectra. The methods are applied to the partial ABS spectrum of a three-terminal Josephson junction realized in an InAs/Al heterostructure, which is extracted from spectroscopic measurements with the help of a deep-learning algorithm. The authors' analysis confirms the existence of quartets in these hybrid structures and illustrates their close relationship with ABS hybridization.