Harnessing non-Hermitian Scattering Dynamics for Enhanced Sensing

Non-Hermitian physics is rapidly evolving from a theoretical endeavor to an experimental framework where tunable dissipation, amplification, and non-reciprocal coupling can be used to explore symmetry breaking and develop enhanced sensing platforms. Exceptional points (EPs), spectral degeneracies of non-Hermitian Hamiltonians, have been studied extensively for their potential to enhance sensor performance by leveraging a square-root eigenvalue response to perturbations, but their direct role in sensing is limited by unavoidable noise amplification in thier vicinity. Here, we instead investigate degeneracies of the non-Hermitian transmission scattering matrix, mwhich are directly observable in experients. We explore transmission peak degeneracies (TPDs), which retain the square-root sensitivity associated with EPs while avoiding their intrinsic noise penalty. Using a fully tunable microwave magnon–photon dimer with independent control over resonant frequencies, dissipation, and coupling phase, we realize and characterize EP–TPD pairs spanning parity-time (PT), anti-PT, and anyonic-PT symmetries, while introducing analytic figures of merit that quantify potential sensing performance under magnetic field and voltage perturbations. Beyond sensing, this versatile platform enables exploration of synthetic photonic–magnon lattices, non-Hermitian topological phases, and generalized symmetry-breaking phenomena in classical and open quantum systems.