Topological protection of photon-pair generation in nonlinear waveguide arrays

TL;DR

This paper demonstrates that topological effects in nonlinear waveguide arrays can significantly protect photon-pair generation from disorder, enhancing robustness for quantum photonic applications.

Contribution

It provides the first systematic comparison showing topological arrays preserve SPDC resonance stability under disorder, supported by experimental and analytical evidence.

Findings

Topological arrays maintain stable SPDC resonance spectra despite disorder.

Resonance fluctuations are reduced by over an order of magnitude in topological configurations.

Analytical models link robustness to band-structure properties of interacting modes.

Abstract

Harnessing topological effects offers a promising route to protect quantum states of light from imperfections, potentially enabling more robust platforms for quantum information processing. This capability is particularly relevant for active photonic circuits that generate quantum light directly on-chip. Here, we explore topological effects on photon-pair generation via spontaneous parametric down-conversion (SPDC) in nonlinear waveguide arrays, both theoretically and experimentally. A systematic comparison of homogeneous, trivial, and topological Su-Schrieffer-Heeger arrays reveals that only the topological configuration preserves a stable SPDC resonance spectrum under disorder in the tunnel couplings, with fluctuations in the resonance position reduced by more than one order of magnitude. An analytical model supports our experimental observations by linking this robustness to the band-structure properties of the interacting modes. These findings establish quadratic nonlinear waveguide arrays as a promising platform to explore the interplay of nonlinearity, topology, and disorder in quantum photonic circuits.