The impossibility of partially local hidden variable models for quantum theory and the relation to cryptography

          @misc{ scivideos_PIRSA:08120037,
            doi = {10.48660/08120037},
            url = {https://pirsa.org/08120037},
            author = {Colbeck, Roger},
            keywords = {Quantum Foundations},
            language = {en},
            title = {The impossibility of partially local hidden variable models for quantum theory and the relation to cryptography},
            publisher = {Perimeter Institute for Theoretical Physics},
            year = {2008},
            month = {dec},
            note = {PIRSA:08120037 see, \url{https://scivideos.org/pirsa/08120037}}
          }
          

Abstract

More than 40 years ago, Bell ruled out completely local hidden variable models as an explanation for quantum correlations. However, a new type of hidden variable model has recently been brought to light by the work of Leggett. Such a model has both local and non-local parts. Roughly speaking, having a local part means that the measurement outcomes can be guessed with better than 50% success. In this talk, I will explain that there exist quantum correlations for which any hidden variable model must have a trivial local part. I will then discuss how an extension of the original theorem implies that these correlations can be used to enhance the quality of a private random string.