Entangled multiphoton states lie at the heart of quantum information, computing, and communications. In recent years, topology has risen as a new avenue to robustly transport quantum states in the presence of fabrication defects, disorder and other noise sources. Whereas topological protection of single photons and correlated photons has been recently demonstrated experimentally, the observation of topologically protected entangled states has thus far remained elusive. Here, we experimentally demonstrate the topological protection of spatially-entangled biphoton states. We observe robustness in crucial features of the topological biphoton correlation map in the presence of deliberately introduced disorder in the silicon nanophotonic structure, in contrast with the lack of robustness in nontopological structures. The topological protection is shown to ensure the coherent propagation of the entangled topological modes, which may lead to robust propagation of quantum information in disordered systems. The discovery of topological insulators has stimulated the design of topological systems across many platforms beyond condensed matter, including electromagnetism [1]-[9], ultracold atoms [10],[11] and phonons [12]-[14]. In all these systems, the unique topology of the wave functions

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We report our experimental demonstration of biphoton entanglement between topologically-distinct modes in a bipartite silicon photonics lattice. These results highlight topology as a degree of freedom for entanglement and could have implications in quantum information.

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We report our experimental results on topologically protected path-entangled photonic states using dimer chains in silicon photonics. These results highlight the potential of the lattice topology to protect photonic quantum information.