ABSTRACT
The measurement problem is the most central and persistent issue in the interpretation of quantum mechanics. It has been described in many ways, the most eloquent being that given by Wigner in the following way: quantum theory says that quantum systems evolve linearly, deterministically, continuously and reversibly according to the Schrödinger equation, except when we perform a measurement on the system. When measuring the value of an observable, whose wave function is not an eigenfunction to the operator representing the measured observable, the measurement is nonlinear, discontinuous, non-deterministic and irreversible. The superposition state changes, as a result of the measurement, into one of its components. In other words, the measurement induces a collapse of the wave function (Wigner, 1983). Why so? What is so special about measurements? After all, measurements are, disregarding our cognitive use of them, ordinary physical interactions and the Schrödinger equation offers a precise theoretical description of all physical interactions. But then, measurements ought to be continuous, deterministic and reversible, which they are not.
