QBism

Measured by the accuracy of its predictions and the scope of its technological applications, quantum mechanics is arguably the most successful theory in science. Ironically, it is also one of the least well understood. Here the conventional view of quantum mechanics is outlined in simple, non-mathematical language, with emphasis on its most puzzling features. The key to understanding is probability, a common, everyday concept that turns out to be surprisingly problematic. Until 2002 all of the alternative interpretations of quantum mechanics relied on the modern, orthodox definition of…