In 1967 R. L. Pfleegor and L. Mandel, Phys. Lett. 24A, 766-67
proved experimentally the self-interaction of photon through double slit.
Well, some said it is even later until 1986 by Grangier et al.
However, recent years quantum mechanics has changed a lot.
What are the latest understanding about this issue theoretically?
Do people still consider it as mystical? Due to quantum superposition?