Quantum Discord: Bipartite Correlations

Quantum Discord

For a 2-qubit state ρ, quantum discord D = I(A:B) − J(A:B) where J is the classical information gained by measuring B. Discord ≥ 0, equals entanglement for pure states.

I(A:B) = S(A)+S(B)−S(AB)
J = S(A)−min_Π S(A|Π_B)
D = I − J ≥ 0

Entanglement θ (|ψ⟩=cos θ|00⟩+sin θ|11⟩): 0.39 Mixing p (ρ = p|ψ⟩⟨ψ|+(1-p)I/4): 0.80 Rotation φ (local unitary on B): 0.00

S(AB)-

S(A)-

S(B)-

I(A:B)-

J(A:B)-

Discord D-

Entanglement E-

Concurrence C-