Quantum discord bounds the amount of distributed entanglement

"The ability to distribute quantum entanglement is a prerequisite for many fundamental tests of quantum theory and numerous quantum information protocols. Two distant parties can increase the amount of entanglement between them by means of quantum communication encoded in a carrier that is sent from one party to the other. Intriguingly, entanglement can be increased even when the exchanged carrier is not entangled with the parties. However, in light of the defining property of entanglement stating that it cannot increase under classical communication, the carrier must be quantum. In this talk I will show that, in general, the increase of relative entropy of entanglement between two remote parties is bounded
by the amount of non-classical correlations of the carrier with the parties as quantified by the relative entropy of discord."