Figure 1. Genuine entanglement of two QEs inserted in the gaps of a linearly arranged silver nanosphere trimer (shown in inset) with various separation distances and frequencies:

(a) d = 4 nm and ω₁ = 4920 THz; (b) d = 2 nm, ω₁ = 4770 THz(solid), ω₂ = 5010 THz (dashed); (c) d = 1 nm, ω₁ = 4530 THz (solid), ω₂ = 4800 THz (dashed). The radii of nanospheres are R = 10 nm, and the orientations of electric dipole moments for two QEs are both along the axis of the trimer.