Photonic zero mode in a non-Hermitian photonic lattice

TLDR

Zero‑energy quasiparticles such as Majorana fermions are predicted to enable fault‑tolerant quantum computation, yet in conventional Hermitian systems they are fragile and can vanish when coupled to environments of the same topological character. The study demonstrates a robust photonic zero mode maintained by a spatial non‑Hermitian phase transition in a PT‑symmetric lattice, even when the entire system shares the same topological order. The authors construct a PT‑symmetric lattice of two semi‑lattices in distinct PT phases whose decoupled real spectra at the interface provide non‑Hermitian‑enhanced topological protection, and they confirm the zero mode experimentally using ultrafast heterodyne measurements of light transport in a silicon waveguide lattice. The zero mode resides at the midgap of the PT‑symmetric spectrum and remains topologically protected against disorder, as verified by the ultrafast heterodyne measurements of light transport in the silicon waveguide lattice.

Abstract

Abstract Zero-energy particles (such as Majorana fermions) are newly predicted quasiparticles and are expected to play an important role in fault-tolerant quantum computation. In conventional Hermitian quantum systems, however, such zero states are vulnerable and even become vanishing if couplings with surroundings are of the same topological nature. Here we demonstrate a robust photonic zero mode sustained by a spatial non-Hermitian phase transition in a parity-time (PT) symmetric lattice, despite the same topological order across the entire system. The non-Hermitian-enhanced topological protection ensures the reemergence of the zero mode at the phase transition interface when the two semi-lattices under different PT phases are decoupled effectively in their real spectra. Residing at the midgap level of the PT symmetric spectrum, the zero mode is topologically protected against topological disorder. We experimentally validated the robustness of the zero-energy mode by ultrafast heterodyne measurements of light transport dynamics in a silicon waveguide lattice.