Multipartite bound information exists and can be activated.
We prove the conjectured existence of bound information, a classical analog of bound entanglement, in the multipartite scenario. We give examples of tripartite probability distributions from which it is impossible to extract any kind of secret key, even in the asymptotic regime, although they cannot be created by local operations and public communication. Moreover, we show that bound information can be activated: three honest parties can distill a common secret key from different distributions having bound information. Our results demonstrate that quantum information theory can provide useful insight for solving open problems in classical information theory.
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Institut de Ciències Fotòniques, Jordi Girona 29, Edifici Nexus II, 08034 Barcelona, Spain.
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