O ne of the most confounding concepts to emerge from the cauldron of early 20th-century physics was the idea that quantum objects can exist in multipl

Can AI Save Schrödinger’s Cat?

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2024-11-07 16:00:16

O ne of the most confounding concepts to emerge from the cauldron of early 20th-century physics was the idea that quantum objects can exist in multiple states simultaneously. A particle could be in many places at once, for example. The math and experimental results were unequivocal about it. And it seemed that the only way for a particle to go from such a “superposition” of states to a single state was for someone or something to observe it, causing the superposition to “collapse.” This bizarre situation raised profound questions about what constitutes an observation or even an observer. Does an observer merely discover the outcome of a collapse or cause it? Is there even an actual collapse? Can an observer be a single photon, or does it have to be a conscious human being?

This last question was highlighted in 1961 by Hungarian physicist Eugene Wigner, who came up with a thought experiment involving himself and an imaginary friend. The friend is inside a fully isolated laboratory, making observations of a quantum system that’s in a superposition of two states: say, one that causes a flash of light and one that doesn’t. Wigner is outside, observing the entire lab. If there’s no interaction between the lab and the external world, the whole lab evolves according to the rules of quantum physics, and the experiment presents a contradiction between Wigner’s observations and those of his friend. The friend presumably perceives an actual result (flash or no flash), but Wigner must regard the friend and the lab as being in a superposition of states: one where a flash is produced and the friend sees it, and one where there is no flash and the friend does not see anything. (The friend’s state is not unlike that of Schrödinger’s cat while it is dead and alive at the same time.)

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