Measurement

Abstract

The purpose of a measurement is the determination of properties of the physical system under investigation. In this sense the general conception of measurement is that of an unambiguous comparison: the object system prepared in a state is brought into a suitable contact—a measurement coupling—with another, independently prepared system, the measuring apparatus, from which the result related to the measured observable is determined by reading the value of the pointer. It is the task of the quantum theory of measurement to investigate measuring processes as physical processes subject to quantum mechanics, and to describe how the stages and steps described above are realised.