Two-photon edge states in photonic topological insulators: topological protection versus degree of entanglement

TL;DR

This paper investigates the robustness of entangled two-photon states in photonic topological insulators, revealing how entanglement degree affects their topological protection and proposing guidelines to optimize their stability for quantum information applications.

Contribution

It identifies mechanisms affecting entangled states in topological photonic lattices and provides strategies to maximize entanglement while maintaining topological protection.

Findings

High entanglement can lead to rapid deterioration of two-photon states in disordered lattices.

Physical mechanisms influencing entanglement vulnerability are characterized.

Guidelines for balancing entanglement and topological protection are proposed.

Abstract

Topological insulators combine insulating properties in the bulk with scattering-free transport along edges, supporting dissipationless unidirectional energy and information flow even in the presence of defects and disorder. The feasibility of engineering quantum Hamiltonians with photonic tools, combined with the availability of entangled photons, raises the intriguing possibility of employing topologically protected entangled states in optical quantum computing and information processing. However, while two-photon states built as a product of two topologically protected single-photon states inherit full protection from their single-photon "parents", high degree of non-separability may lead to rapid deterioration of the two-photon states after propagation through disorder. We identify physical mechanisms which contribute to the vulnerability of entangled states in topological photonic lattices and present clear guidelines for maximizing entanglement without sacrificing topological protection.