Experimental demonstration of quantum pigeonhole paradox.

Chen, Ming-Cheng; Liu, Chang; Luo, Yi-Han; Huang, He-Liang; Wang, Bi-Ying; Wang, Xi-Lin; Li, Li; Liu, Nai-Le et al. · Proc Natl Acad Sci U S A · 2019

basic_science · Level V

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Abstract

We experimentally demonstrate that when three single photons transmit through two polarization channels, in a well-defined pre- and postselected ensemble, there are no two photons in the same polarization channel by weak-strength measurement, a counterintuitive quantum counting effect called the quantum pigeonhole paradox. We further show that this effect breaks down in second-order measurement. These results indicate the existence of the quantum pigeonhole paradox and its operating regime.