Violations of local realism by two entangled quNits

Results obtained in two recent papers, (Kaszlikowski D, Gnacinski P, Zukowski M, Miklaszewski W and Zeilinger A 2000 Phys. Rev. Lett. 85 4418 and Durt T, Kaszlikowski D and Zukowski M 2001 Preprint quant-ph/0101084) seem to indicate that the nonlocal character of the correlations between the outcomes of measurements performed on entangled systems separated in space is not robust in the presence of noise. This is surprising, since entanglement itself is robust. Here we revisit this problem and argue that the class of gedanken experiments considered in the two recent papers listed above is too restrictive. By considering a more general class, involving sequences of measurements, we prove that the nonlocal correlations are in fact robust.

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