The entropy of entanglement is an entanglement measure for a bipartite pure states. It is defined as the von Neumann entropy of one of the reduced states. That is, for a pure state ρ_AB = ∣Ψ⟩⟨Ψ∣_AB, it is given by:

E(ρ) ≡ S(ρ_A) = S(ρ_B)
,

where ρ_A = Tr_B(∣Ψ⟩⟨Ψ∣) and ρ_B = Tr_A(∣Ψ⟩⟨Ψ∣).

Many entanglement measures reduce to the entropy of entanglement when evaluated on pure states. Among those are

• Distillable entanglement
• Entanglement cost
• Entanglement of formation
• Relative entropy of entanglement
• Squashed entanglement

Some entanglement measures that do not reduce to the entropy of entanglement are

• Negativity
• Logarithmic negativity
• Robustness of entanglement

See also

• Quantum relative entropy

Category:Entropy Category:Handbook of Quantum Information Category:Entanglement