måleproblemets

Måleproblemets is the Swedish-language expression for what is commonly called the quantum measurement problem. It concerns how a quantum system described by a linear, unitary evolution can produce a definite outcome with a specific probability distribution when a measurement is performed, given that the theory allows superpositions that can extend to macroscopic scales. The issue lies at the heart of how the formalism translates into the definite results observed in experiments.

Core elements of the problem include the role of the wavefunction and its collapse, the status of measurements, and the origin of the Born rule for probabilities. The tension arises because the Schrödinger equation governs continuous, deterministic evolution, while measurements appear to produce probabilistic, singular outcomes that do not, in an obvious way, follow from that evolution.

A range of interpretations and approaches have been proposed to address måleproblemets. The Copenhagen interpretation posits a special role for measurement and a collapse of the wavefunction. Many-Worlds suggests that all possible outcomes occur in branching universes. Objective collapse theories modify dynamics to include spontaneous collapses. De Broglie–Bohm pilot-wave theory preserves a deterministic evolution with hidden variables. Decoherence theory explains the apparent emergence of classicality through environment-induced suppression of interference, but it does not in itself select a single outcome.

Today, måleproblemets remains a central topic in the foundations of quantum mechanics. There is no consensus on a unique solution, but ongoing work in interpretation, quantum information, and experimental tests of collapse models continues to illuminate how quantum probabilities relate to observed facts.