Superposition: Before a measurement, a quantum particle can exist in a superposition of multiple states: it can occupy multiple positions or have multiple values simultaneously.
Measurement interaction: When a measurement is performed on the system, it interacts with the quantum system, causing the wave function to "collapse" into a single, definite state, giving a specific value for the measured quantity. Then:
Probability interpretation: The wave function before collapse provides the probabilities of obtaining different possible outcomes upon measurement, or...
Copenhagen interpretation: This interpretation of quantum mechanics associates the collapse of the wave function with the act of observation by a conscious observer, or...
Many Worlds interpretation: measurement does not collapse the wave function, it merely samples one possibility. All other possibilities are also physically actualized in the Multiverse.
Many Worlds interpretation: measurement does not collapse the wave function, it merely samples one possibility. All other possibilities are also physically actualized in the Multiverse.