We experimentally demonstrate that entanglement of bi-photon polarization state can be restored by spectral filters. This restoration procedure can be viewed as a new class of quantum eraser, which retrieves entanglement rather than just interference by manipulating an ancillary degree of freedom.
@article{arxiv.quant-ph/0107121,
title = {Restoration of Entanglement by Spectral Filters},
author = {K. Usami and Y. Nambu and S. Ishizaka and T. Hiroshima and Y. Tsuda and K. Matsumoto and K. Nakamura},
journal= {arXiv preprint arXiv:quant-ph/0107121},
year = {2007}
}