Many quantum information protocols require a Bell-state measurement of entangled systems. Most optical Bell-state measurements utilize two-photon interference at a beam splitter. By creating polarization-entangled photons with spontaneous parametric down-conversion using a first-order Hermite-Gaussian pump beam, we invert the usual interference behavior and perform an incomplete Bell-state measurement in the coincidence basis. We discuss the possibility of a complete Bell-state measurement in the coincidence basis using hyperentangled states [Phys. Rev. A, \textbf{58}, R2623 (1998)].
@article{arxiv.quant-ph/0212058,
title = {Optical Bell-state analysis in the coincidence basis},
author = {S. P. Walborn and W. A. T. Nogueira and S. Pádua and C. H. Monken},
journal= {arXiv preprint arXiv:quant-ph/0212058},
year = {2009}
}