text: Eugene Wigner extended it by adding a friend who acts as an intermediary, describing the result to the titular person when he returns to the lab.
full_question: Eugene Wigner extended it by adding a friend who acts as an intermediary, describing the result to the titular person when he returns to the lab. This thought experiment was put forth as a macroscopic demonstration of the seemingly impossible concept of eigenstate presented by the Copenhagen interpretation. Further analysis of this thought experiment gave rise to the concept of quantum entanglement. Put forth by its namesake Austrian physicist, this is for ten points what thought experiment involving a box, a flask of hydrocyanic acid, and a namesake feline?
first_sentence: Eugene Wigner extended it by adding a friend who acts as an intermediary, describing the result to the titular person when he returns to the lab.