Quantum mechanics operates on probabilities rather than certainties. A fundamental concept is the state of a quantum system, which can be represented as a wave function that encompasses a superposition of states. Each possible state has a certain probability amplitude, and the act of measurement causes this wave function to 'collapse' to a particular eigenstate, a process often misrepresented as the observer effect. Prior to measurement, the system exists in a superposition, where all possibilities coexist in a probability distribution.
Measurement, a central yet enigmatic aspect of quantum mechanics, prompts the transition from potential outcomes to a definitive reality. This collapse is not attributed to any physical force but is a postulate of quantum theory to match observed reality with mathematical predictions. However, the nature of wave function collapse remains a subject of philosophical debate and is unresolved within the framework of quantum mechanics.
The notion of collapse distinguishes quantum mechanics from classical physics, which relies on deterministic laws. In quantum systems, each observation removes the element of statistical interferences inherent in superpositions, converging to a single state out of an ensemble of possibilities. Some interpretations, such as the Copenhagen interpretation, assert that the collapse is an inherent part of quantum processes, while other interpretations, including many-worlds, propose that all possibilities continue to exist in separate, non-communicating branches of the universe. Therefore, measurement in quantum mechanics introduces a level of indeterminism absent from classical systems, reflecting the fundamental unpredictability of quantum states prior to observation.