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Quantum

Quantum

Wigner’s friend: the quantum thought experiment that continues to confound

18 Mar 2024 Robert P Crease

“Wigner’s friend” is a curious thought experiment that has stumped physicists and philosophers for more than 60 years. Robert P Crease, Jennifer Carter and Gino Elia advise on how to resolve this conundrum

Quantum mystery In 1961 Eugene Wigner imagined a friend doing an experiment in a lab while he waits outside. The paradox is that Wigner and the friend predict different outcomes, yet both are right. (iStock/Floriana)
The quantum world provides fertile material for thought experiments that seem so strange-but-true as

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Robert P Crease is a professor in the Department of Philosophy, Stony Brook University, US and writes the monthly Critical Point column for Physics World, robertpcrease.com, e-mail robert.crease@stonybrook.edu. His latest book is The Leak: Politics, Activists, and Loss of Trust at Brookhaven National Laboratory
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