I know, that for a compound system $ |\psi \rangle_{AB} $ we can find the Schmidt basis, which is an unique one. Is it at the same time the basis, in which the two subsystems are minimally entangled?
If so, how this can be proved / disproved?
I think it would make sense to say, that when the Schmidt rank is equal to 1, the system is separable, because in the basis minimizing the entanglement we can represent the state $|\psi \rangle_{AB} $ as a product of two substates $ |\psi \rangle_A \otimes |\psi \rangle_B $.