S. P. Walborn, W.A.T. Nogueira , S. Pádua and C.H. Monken
EUROPHYSICS LETTERS 62, 2 (2003)
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 downconversion 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, 58 (1998) R2623).