# Measurements of Nonlocal Variables and Demonstration of the Failure of the Product Rule for a Pre- and Postselected Pair of Photons.

@article{Xu2019MeasurementsON, title={Measurements of Nonlocal Variables and Demonstration of the Failure of the Product Rule for a Pre- and Postselected Pair of Photons.}, author={Xiao-Ye Xu and Wei-Wei Pan and Qin-Qin Wang and Jan Dziewior and Lukas Knips and Yaron Kedem and Kai Sun and Jin-Shi Xu and Yongjian Han and Chuan-Feng Li and Guangcan Guo and Lev Vaidman}, journal={Physical review letters}, year={2019}, volume={122 10}, pages={ 100405 } }

We report the first implementation of the von Neumann instantaneous measurements of nonlocal variables, which becomes possible due to technological achievements in creating hyperentangled photons. Tests of reliability and of the nondemolition property of the measurements have been performed with high precision, showing the suitability of the scheme as a basic ingredient of numerous quantum information protocols. The method allows us to demonstrate for the first time with strong measurements a…

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