Qubit Entanglement Breaking Channels

Abstract

This paper continues the study of stochastic maps, or channels, for which (I⊗Φ)(Γ) is always separable in the case of qubits. We give a detailed description of entanglement-breaking qubit channels, and show that such maps are precisely the convex hull of those known as classical-quantum channels. We also review the complete positivity conditions in a canonical parameterization and show how they lead to entanglement-breaking conditions.