Mätpostulatet

Mätpostulatet, or the measurement postulate, is a fundamental concept in quantum mechanics that describes the act of measuring a quantum system. It states that when a measurement is performed on a quantum system, the system's state collapses instantaneously into one of the possible eigenvalues of the observable being measured. The probability of collapsing into a specific eigenstate is determined by the square of the amplitude of the corresponding eigenvector in the system's original quantum state.

Prior to measurement, a quantum system can exist in a superposition of multiple states, meaning it simultaneously possesses characteristics of different possible outcomes. The act of measurement forces the system to commit to a single definite state. This is often contrasted with classical physics, where measurement is generally assumed to disturb the system in a predictable and less drastic way. The mätpostulatet implies that the observer and the observed system are intrinsically linked during the measurement process.

The mätpostulatet is a cornerstone of the Copenhagen interpretation of quantum mechanics. It has significant implications for understanding phenomena such as quantum entanglement and the uncertainty principle. While mathematically well-defined, the precise physical mechanism behind state collapse remains a subject of ongoing debate and theoretical exploration within the field of quantum foundations. Different interpretations of quantum mechanics offer varying perspectives on what constitutes a "measurement" and how state collapse occurs.