Ten theorems about quantum mechanical measurements

Abstract

The aim of quantum mechanics is to explain macroscopic, objectively recorded phenomena. Microscopic objects are measured by enabling them to interact with a macroscopic measuring apparatus prepared in a metastable state. Macroscopic objects, such as cats, are not above the laws of quantum mechanics, but owing to their enormously dense level spectrum other aspects than single eigenvalues and eigenfunctions are prominent. These aspects can be described in classical terms, such as probabilities instead of probability amplitudes. The measuring act is fully described by the Schrödinger equation for object system and apparatus together. The collapse of the wave function is a consequence rather than an additional postulate. A model is constructed to demonstrate these statements. It also appears that the entropies of the object system and the apparatus increase by the same amount, namely the entropy difference between the metastable initial state and the stable final state of the apparatus.