We briefly review measurement theory in quantum mechanics and also the development of decoherence theory. We present decoherence theory using a simple two-level system to illustrate some of its main implications and limitations as a solution to measurement theory. Next, we present a new interpretation of quantum mechanics called the Montevideo interpretation, based on the introduction of realistic clocks in the evolution of a quantum system. The Montevideo interpretation establishes the concept of undecidability that allows defining an event. In general, the Montevideo interpretation fits the relational interpretation of quantum mechanics, which interprets the value of a given quantity in connection with variations in the values of other quantities. We hope that this presentation will introduce physics students to current issues in measurement theory.
Keywords:
Quantum mechanics; theory of measurement; decoherence; the Montevideo interpretation