Coherent interactions that generate negligible entanglement can still exhibit unique quantum behaviour. This observation has motivated a search beyond entanglement for a complete description of all quantum correlations. Quantum discord is a promising candidate. Here, we demonstrate that under certain measurement constraints, discord between bipartite systems can be consumed to encode information that can only be accessed by coherent quantum interactions. The inability to access this information by any other means allows us to use discord to directly quantify this ‘quantum advantage’. We experimentally encode information within the discordant correlations of two separable Gaussian states. The amount of extra information recovered by coherent interaction is quantified and directly linked with the discord consumed during encoding. No entanglement exists at any point of this experiment. Thus we introduce and demonstrate an operational method to use discord as a physical resource.
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We thank C. Weedbrook, J. Thompson, N. Walk and H. Wiseman for helpful discussions. The research is supported by the National Research Foundation and Ministry of Education in Singapore (M.G., K.M. and V.V.), the John Templeton Foundation (K.M. and V.V.), and the Australian Research Council Centre of Excellence for Quantum Computation and Communication Technology (Project number CE110001027). (H.C., S.M.A., T.S., T.C.R. and P.K.L.).
The authors declare no competing financial interests.
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Gu, M., Chrzanowski, H., Assad, S. et al. Observing the operational significance of discord consumption. Nature Phys 8, 671–675 (2012). https://doi.org/10.1038/nphys2376
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