Schematic diagram following one in "A double-slit quantum eraser" by Walborn, Cunha, Pádua, and Monken. In this configuration the polarizer (POL1) inserted in the path leading to the detector in the signal path causes opposing circular polarizations to emerge in both paths leading from the double slits, allowing photon self-interference to occur at the detector screen and permitting interference fringes to be observed.
Own work
Patrick Edwin Moran