Popper’s experiment realized again—but what does it mean?

Illustration of Popper’s experiment realized with randomly paired photons in a thermal state. In the second set-up, there is no “slit B” for the photon on the right. The new results show that this photon is not affected by a measurement on the left photon (which does travel through a slit), in agreement with Popper’s prediction. Credit: Tao Peng, et al. ©2015 EPLA

Illustration of Popper’s experiment realized with randomly paired photons in a thermal state. In the second set-up, there is no “slit B” for the photon on the right. The new results show that this photon is not affected by a measurement on the left photon (which does travel through a slit), in agreement with Popper’s prediction. Credit: Tao Peng, et al. ©2015 EPLA

Like Einstein, the philosopher Karl Popper was a realist who was deeply bothered by some of the odd implications of quantum mechanics. Both Popper and Einstein disliked the idea in Heisenberg’s uncertainty principle, for instance, that precisely measuring one property of a particle means that the particle’s conjugate property is completely undetermined. This idea undermines the basic principle of common-sense realism: that every particle’s properties must have precise pre-existing values, which do not depend on being measured.
Both Popper and Einstein proposed thought experiments critiquing the uncertainty principle. But while Einstein, Podolsky, and Rosen’s EPR experiment is quite famous, Popper’s experiment is not as widely known.

Popper first published his proposed experiment in 1934, and in 1999, physicists Yoon-Ho Kim and Yanhua Shih realized Popper’s experiment for the first time. In what came as a surprise to many, their results agreed with Popper’s predictions, yet are not generally considered to be a true violation of the uncertainty principle, as Popper believed. The findings ignited a great deal of critique, both of Popper’s original ideas and how they might be realized and interpreted.
Now in a new study published in EPL, Shih and coauthors at the University of Maryland in Baltimore and Oakland Community College in Waterford, Michigan, have again realized Popper’s experiment using a different approach. Once again, their results agree with Popper’s predictions, yet still do not violate the uncertainty principle. However, the researchers explain that the results do reveal a concern about nonlocal interference, as the observations suggest that a pair of particles is instantaneously interfering with itself, even across large distances…
… Read more at http://phys.org/news/2015-01-popper-againbut.html

Read also: Popper’s Experiment and the Uncertainty Principle

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