• C S SUDHEER KUMAR

      Articles written in Pramana – Journal of Physics

    • Violation of space–time Bell-CHSH inequality beyond the Tsirelson bound and quantum cryptography

      C S SUDHEER KUMAR

      More Details Abstract Fulltext PDF

      Here we show that if we insert context-dependent local unitary evolutions into the spatial (i.e. normal) Bell–Clauser–Horne–Shimony–Holt (Bell-CHSH) test, then it is possible to violate the space–time Bell-CHSH inequality maximally (i.e. up to 4). The correct context dependency can be achieved via post-selection. However, this does not contradict the Tsirelson quantum bound ($2\sqrt{2}$), because the latter has been derived without taking into consideration the context-dependent unitary evolutions and/or post-selection. As an important application, this leads to a more efficient (in terms of resource (singlets) and classical communication) and more sensitive (to eavesdropping) quantum key distribution (QKD) protocol, compared to Ekert’s and Wigner’s QKD protocols.

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