Deciding whether a quantum state has secret correlations is an NP-complete problem
arXiv:quant-ph/0612052
Abstract
From the NP-hardness of the quantum separability problem and the relation between bipartite entanglement and the secret key correlations, it is shown that the problem deciding whether a given quantum state has secret correlations in it or not is in NP-complete.
3 pages, revtex, no fig, typos corrected