Topological edge states of interacting photon pairs realized in a topolectrical circuit

Nikita A. Olekhno, Egor I. Kretov, Andrey A. Stepanenko, Dmitry S. Filonov, Vitaly V. Yaroshenko, Barbara Cappello, Ladislau Matekovits, Maxim A. Gorlach

Published 2019-07-01Version 1

Topolectrical circuits have recently emerged as a simple yet very useful platform for a tabletop realization of topological physics. Employing this platform, we capture an intriguing physics of two-photon topological states in quantum regime going beyond well-celebrated topological states of classical light. Besides their quantum nature, investigated two-photon states also exhibit an interaction-induced origin, elucidating the interplay between quantum entanglement and interactions. In our experiments, we extract the frequencies of bulk and edge two-photon bound states and evaluate the associated topological invariant directly from the measurements. To further enhance our findings, we perform a reconstruction of the two-photon probability distribution for the topological state. Our results shed light onto the topological protection in interacting quantum-optical systems opening further perspectives for applications in quantum communication and quantum computations.