Quantum correlations beyond entanglement in two-qubit Werner states
Correlation Measures
State: Werner ρ(p)
Mutual Info I(A:B): —
Classical Corr J(A:B): —
Quantum Discord D: —
Concurrence C: —
Entanglement E: —
D > 0 even when C = 0
Quantum discord D(A|B) = I(A:B) − J(A:B) captures quantum correlations beyond entanglement. For Werner states ρ(p) = p|Φ⁺⟩⟨Φ⁺| + (1−p)I/4, concurrence vanishes below p = 1/3 but discord remains non-zero for all p > 0. This makes discord a sensitive probe of non-classical correlations even in separable mixed states.