Quantum discord quantifies non-classical correlations going beyond the
standard classification of quantum states into entangled and unentangled ones.
Although it has received considerable attention, it still lacks any precise
interpretation in terms of some protocol in which quantum features are
relevant. Here we give quantum discord its first operational meaning in terms
of entanglement consumption in an extended quantum state merging protocol. We
further relate the asymmetry of quantum discord with the performance imbalance
in quantum state merging and dense coding.Comment: v4: 5 pages, 1 fig. Refs added, text improved. Main results
unchanged. See arXiv:1008.4135v2 for a related work. v5: close to the
published versio
