V_dd: — | Blockade: — | Ω_eff: —
Rydberg: V(r)=C₆/r⁶, C₆∝n¹¹. Blockade radius r_b=(C₆/Ω)^(1/6). Inside r_b: only |W⟩=(|gr⟩+|rg⟩)/√2 accessible.