A quantum measurement on one quantum in an entangled pair can give which-way information or both-way information of the other in the pair. This interesting property of entanglement enables one to perform quantum eraser(QE) experiments including delayed choice QE experiments. I propose several modifications of the delayed choice QE experiment performed by Y.H. Kim et al., and also present theoretical calculations. Finally, I propose the coarse-grained version of QE experiment, which shows the wave-particle duality more clearly than the original QE experiment does, and can also be carried out more easily in experiment.
