Quantum measurements and maps preserving strict convex combinations and pure states

Abstract

In this paper, a characterization of maps between quantum states that preserve pure states and strict convex combinations is obtained. Based on this characterization, a structural theorem for maps between multipartite quantum states that preserve separable pure states and strict convex combinations is established. Then these results are applied to characterize injective (local) quantum measurements and answer some conjectures proposed in [J.Phys.A:Math.Theor. 45 (2012) 205305].