  In this article, we survey some controversial problems concerning the idea of
erasing Which Way information proposed in recent years. A statistical
examination of these proposals suggests that whenever the Bayesian rule is
taken into account for two relevant events in two successive times, the
probabilistic description of them is unavoidably time-symmetric. Consequently,
it seems that they cannot fulfill the implications of a so-called
delayed-choice experiment. As a possible alternative, however, we suggest a new
experimental arrangement in which one can change the whole state of a given
system at a proper time (without measurement) to accomplish an actual
delayed-choice experiment with a time-asymmetric attribute. The peculiar
features of this experiment are then discussed.
