# Delayed choice experiments and causality in quantum mechanics. (arXiv:1907.05990v1 [quant-ph])

Although it may seem The Delayed Choice experiments contradict causality and
one could construct an experiment which could possibly affect the past, using
Many World interpretation we prove it is not possible. We also find a
mathematical background to Which-path information and show why its
obtainability prevents system from interfering. We find a system which exhibit
both interference and correlation and show why one-particle interference and
correlations are complementary. Better visible interference pattern leads to
worse correlations and vice versa. Then, using knowledge gained from Quantum
Eraser and Delayed Choice experiments we prove there is not an objective
reality in a sense of Einstein, Podolsky and Rosen. Furthermore, we discuss the
difference between outer'' (non-interacting) and inner'' (interacting)
observer. We find the mathematical relationship between the universal'' wave
function used by outer'' observer and processes the inner'' observer sees,
which is our small contribution to the measurement problem.