A paradigm for entanglement theory based on quantum communication
  Here it is shown that the squashed entanglement has an operational meaning -- it is the fastest rate at which a quantum state can be sent between two parties who share arbitrary side-information. Likewise, the entanglement of formation and entanglement cost is shown to be the fastest rate at which a quantum state can be sent when the parties have access to side-information which is maximally correlated. A further restriction on the type of side-information implies that the rate of state transmission is given by the quantum mutual information. This suggests a new paradigm for understanding entanglement and other correlations. Different types of side-information correspond to different types of correlations with the squashed entanglement being one extreme. The paradigm also allows one to classify states not only in terms of how much quantum communication is needed to transfer half of it, but also in terms of how much entanglement is needed. Furthermore, there is a dual paradigm: if one distributes the side-information as maliciously as possible so as to make the sending of the state as difficult as possible, one finds maximum rates which give interpretations to known quantities (such as the entanglement of assistance), as well as new ones. The infamous additivity questions can also be recast and receive an operational interpretation in terms of maximally correlated states. 
Jonathan Oppenheim