Fidelity of recovery, squashed entanglement, and measurement recoverability

This paper defines the fidelity of recovery of a tripartite quantum state on systems $A,\phantom{\rule{0.16em}{0ex}}B$, and $C$ as a measure of how well one can recover the full state on all three systems if system $A$ is lost and a recovery operation is performed on system $C$ alone. The surprisal of the fidelity of recovery (its negative logarithm) is an information quantity which obeys nearly all of the properties of the conditional quantum mutual information $I(A;B|C)$, including non-negativ