Copenhagen interpretation

The Copenhagen interpretation is the traditional interpretation of quantum mechanics, associated with Niels Bohr and Werner Heisenberg in the late 1920s. In it, a quantum system is described by a wave function that evolves smoothly until it is measured, at which point the wave function collapses and the system takes on a single definite value, with probabilities for the outcomes given by the Born rule.

#Status

The Copenhagen interpretation treats the measurement result as fundamental and does not describe what, if anything, happens physically during collapse; some versions deny that the wave function represents an objective reality at all. It was the dominant view for much of the twentieth century and is still often taught first. It is, however, only one interpretation among several, and its treatment of measurement as a special process is exactly what the measurement problem questions. Rival accounts include hidden-variable theories and the many-worlds interpretation.