ξ²: — | ΔJ_⊥: — | Gain (dB): —
One-axis twisting: H=χJ_z². Squeezing parameter ξ²=N·min(ΔJ_⊥)²/⟨J_x⟩². Optimal: ξ²_min≈N^(-2/3) at χt∝N^(-2/3). Entanglement witness.