Can a quantum measurement be unitary and still pick one outcome?

Orthodox quantum mechanics insists that evolution is always unitary, yet measurements mysteriously produce single definite outcomes — a tension at the heart of the measurement problem. By assuming both hold simultaneously, this work derives a quantitative bound on how much the environment must remember the pre-measurement state of the system. An experiment testing that memory bound could either expose a contradiction in standard quantum mechanics or reveal that the textbook von Neumann measurement model needs revision.