Photon Pair Survival Rates Through Non-Hermitian SSH Lattices

The interplay of quantum light with non-Hermitian topological systems is a novel field showing surprising dynamics (1, 2). Here, we study quantum walks of photon pairs of different characteristics, i.e. distinguishable vs. indistinguishable photons, in passive non-Hermitian Su-Schrieffer-Heeger lattices. Using the robustness of topological protection, we study how quantum states can systematically avoid losses in passive systems. To probe this behaviour, we launch distinguishable and indistinguishable photon pairs in symmetric and antisymmetric input states into the lattice and record the respective probability of both photons to survive the loss and be detected at the output, a quantity we call the two-photon “survival rate”.