Operational entanglement of symmetry-protected topological edge states

We use an entanglement measure that respects the superselection of particle number to study the nonlocal properties of symmetry-protected topological edge states. Considering half-filled M-leg Su-Schrieffer-Heeger ladders as an example, we show that the topological properties and the operational entanglement extractable from the boundaries are intimately connected. Topological phases with at least two filled edge states have the potential to realize genuine, nonbipartite, many-body entanglement that can be transferred to a quantum register. The entanglement is extractable when the filled edge states are sufficiently localized on the lattice sites controlled by the users. We show, furthermore, that the onset of entanglement between the edges can be inferred from local particle number spectroscopy alone and present an experimental protocol to study the breaking of Bell's inequality.