Figure 1
Schematic of the experimental setup. A \(355 \,\text {nm}\) laser pumps a BBO crystal cut for type-I degenerate downconversion to generate downconverted photon-pairs at \(710 \,\text {nm}\). Lenses \(L_{1}=400 \,\text {mm and } L_{2}=100 \,\text {mm}\) demagnify the beam onto the image plane by a factor of 4 and this plane is then further demagnified onto the detector plane by a factor of 2 by lenses \(L_{3}=100 \,\text {mm and } L_{4}=50 \,\text {mm}\) to give a total demagnification of the beam by a factor of 8 and image the spoke object located in the image plane of the crystal onto the camera.
