Demystifying quantum weirdness in delayed-choice quantum eraser experiment using entangled photons
We have constructed the full density matrix for the quantum eraser experiment using two entangled photons in [Y. Kim et al., Phys. Rev. Lett. 84, 1 (2000)] by tracing the evolution of the initial entangled state to its final state when it reaches the different detectors. Several projective measurements were made on the full density matrix of the entangled system to exhibit the presence or absence of interference fringes which corresponds to the availability of the which path information. The results of the projective measurements agree with the experimental results. Therefore, all the information that can be accessed in the quantum eraser eraser experiment can be obtained in the full density matrix of the system and it is only a matter of postselecting the data points to exhibit the presence or absence of interference fringes.