Out-of-Time-Order Correlators (OTOCs) detect quantum chaos and information scrambling. F(t) = ⟨W†(t)V†W(t)V⟩ decays when operators spread across all qubits.
Left: OTOC F(t) decay over time (blue=integrable, orange=chaotic). Right: operator spreading butterfly cone. Scrambling time t* ~ log(N)/λ_L where λ_L is Lyapunov exponent.