The Born Rule Dies

Understand

The Born rule may be stated mathematically as the rule that probabilities in quantum theory are expectation values of a complete orthogonal set of projection operators.

• This rule works for single laboratory settings in which the observer can distinguish all the different possible outcomes corresponding to the projection operators.
• However, theories of inflation suggest that the universe may be so large that any laboratory, no matter how precisely it is defined by its internal state, may exist in a large number of very distantly separated copies throughout the vast universe.
• In this case, no observer within the universe can distinguish all possible outcomes for all copies of the laboratory.