Feynman’s approach to negative probability in quantum mechanics

Abstract
Feynman introduces the concept of negative probability in the context of Young’s double-slit experiment and in doing so sheds a new light on the problem. However, there are, as Feynman notes, conceptual problems as well as insights associated with this point of view. The micromaser which-path (Welcher-Weg) detector eliminates these conceptual difficulties. We also emphasize that the concept of negative probability yields useful insight into the Einstein-Podolsky-Rosen (EPR) problem.