Title: Collapse of the Wave Function
Headings: Collapse of the Wave Function
Collapse of the Wave Function
What is the Wave Function?
Animation of a wave function collapsing - click to restart
Information Physics Explains the Two-Slit Experiment

Content: Of the several “interpretations” of quantum mechanics, more than half deny the collapse of the wave function. Some of these deny quantum jumps and even the existence of particles! So it is very important to understand the importance of what Dirac called the projection postulate in quantum mechanics. The “collapse of the wave function” is also known as the “reduction of the wave packet.” This describes the change from a system that can be seen as having many possible quantum states (Dirac’s principle of superposition) to its randomly being found in only one of those possible states. Although the collapse is historically thought to be caused by a measurement, and thus dependent on the role of the observer in preparing the experiment, collapses can occur whenever quantum systems interact (e.g., collisions between particles) or even spontaneously (radioactive decay). The claim that an observer is needed to collapse the wave function has injected a severely anthropomorphic element into quantum theory, suggesting that nothing happens in the universe except when physicists are making measurements. An extreme example is Hugh Everett ’s Many Worlds theory, which says that the universe splits into two nearly identical universes whenever a measurement is made. What is the Wave Function? Perhaps the best illustration of the wave function is to show it passing though the famous slits in a two-slit experiment.