Uhlmann's theorem for relative entropies

Giulia Mazzola, David Sutter, Renato Renner

Uhlmann's theorem states that, for any two quantum states ${\rho }_{AB}$ and ${\sigma }_A$, there exists an extension ${\sigma }_{AB}$ of ${\sigma }_A$ such that the fidelity between ${\rho }_{AB}$ and ${\sigma }_{AB}$ equal…