Non-Hermitian Topology in Multiterminal Superconducting Junctions

Recent experimental advancements in dissipation control have yielded significant insights into non-Hermitian Hamiltonians for open quantum systems. Of particular interest are the topological characteristics exhibited by these non-Hermitian systems, that arise from exceptional points-distinct degeneracies unique to such systems. In this Letter, we focus on Andreev bound states in multiterminal Josephson junctions with non-Hermiticity induced by normal metal or ferromagnetic leads. By investigating several systems of different synthetic dimensions and symmetries, we predict fragile and stable non-Hermitian topological phases in these engineered superconducting systems.