Quantum Discord & Bipartite Separability
Quantum correlations beyond entanglement: discord, mutual information, and Werner states
Two-Qubit State
Entanglement parameter α:
0.70
Werner mixing p:
0.80
Local rotation θ_A:
0.00
Local rotation φ_B:
0.00
Concurrence C:
0.000
Entanglement E:
0.000
Mutual Info I:
0.000
Discord D:
0.000
Separable?
Yes
ρ_W = p|ψ⁻⟩⟨ψ⁻| + (1-p)I/4
D(A|B) = I(A:B) - J(A:B)
C = max(0,λ₁-λ₂-λ₃-λ₄)
Quantum discord captures quantum correlations even in separable states (no entanglement). Werner states: entangled iff p > 1/3. Discord = total minus classical correlations. Separability boundary: concurrence = 0.