  A realistic interpretation(REIN) of wave function in quantum mechanics is
briefly presented in this work.
  In REIN, the wave function of a microscopic object is just its real existence
rather than a mere mathematical description. Quantum object can exist in
disjoint regions of space which just as the wave function distributes, travels
at a finite speed, and collapses instantly upon a measurement. The single
photon interference in a Mach-Zehnder interferometer is analyzed using REIN. In
particular, we proposed and experimentally implemented a generalized
delayed-choice experiment, the encounter-delayed-choice(EDC) experiment, in
which the second beam splitter is inserted at the encounter of the two
sub-waves from the two arms. In the EDC experiment, the front parts of wave
functions before the beam splitter insertion do not interfere and show the
particle nature, and the back parts of the wave functions will interfere and
show a wave nature. The predicted phenomenon is clearly demonstrated in the
experiment, and supports the REIN idea.
