  We investigate spontaneous entanglement of two qubits mediated by
nonreciprocal surface plasmon polaritons (SPPs) in a Weyl semimetal. In the
absence of external magnetic fields, the topology of the Weyl semimetal even
gives rise to nonreciprocal SPPs that are topologically protected and reside
inside the photonic gap. We utilize this nonreciprocal SPP as a mediator of
entanglement of two spatially-separated qubits. Our two main findings are: (1)
the nonreciprocal SPP gives better quantum entanglement than the reciprocal
one, and (2) the achieved entanglement is sufficiently long-lived compared to
the entanglement using SPPs in conventional metals.
