Testing the reality of Wigner's friend's experience

Abstract

Quantum mechanics is a robust theory which pro duces highly accurate predictions. Despite its successes, it is still plagued with controversies like the measure- ment problem. In short, the measurement problem is the conflict between the evolution of the wavefunction described by Schro¨dinger’s equation and the apparent collapse of the wavefunction after a measurement is done. The Wigner’s friend paradox illustrates the conflict be- tween the two rules. In the thought experiment, we consider an observer (Wigner’s friend) who is able to per- form measurement on the quantum system and assign a quantum state. Wigner is a super-observer who is able to measure the laboratory his friend is in and also as- sign a quantum state. This process, however, leads to a quantum state that does not ascribe a well-defined value to the outcome of the friend’s observation, in apparent contradiction with the friend’s perspective.