Foundations of Physics

, Volume 29, Issue 12, pp 1849-1861

First online:

Experimental Realization of Popper's Experiment: Violation of the Uncertainty Principle?

  • Yoon-Ho Kim
  • , Yanhua Shih

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An entangled pair of photons (1 and 2) are emitted in opposite directions. A narrow slit is placed in the path of photon 1 to provide the precise knowledge of its position on the y-axis and this also determines the precise y-position of its twin, photon 2, due to quantum entanglement. Is photon 2 going to experience a greater uncertainty in momentum, that is, a greater Δpy because of the precise knowledge of its position y? The experimental data show Δy Δ py < h for photon 2. Can this recent realization of the thought experiment of Karl Popper signal a violation of the uncertainty principle?