Physicists have long suspected that quantum mechanics allows 2 observers to experience different, conflicting realities. Now they’ve performed the first experiment that proves it. They use 6 entangled photons to create 2 alternate realities—1 representing Wigner and 1 representing Wigner’s friend. Wigner’s friend measures the polarization of a photon and stores the result. Wigner then performs an interference measurement to determine if the measurement and the photon are in a superposition. The experiment produces an unambiguous result. It turns out that both realities can coexist even though they produce irreconcilable outcomes, just as Wigner predicted. That raises some fascinating questions that are forcing physicists to reconsider the nature of reality.

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