Generation of entangled photon pairs using small coherence time continuous wave pump lasers

We address the generation of entangled photon pairs by parametric downconversion from solid state cw lasers with small coherence time. We consider a compact and low-cost setup based on a two-crystal scheme with type-I phase matching.We reconstruct the full density matrix by quantum tomography and analyze in detail the entanglement properties of the generated state as a function of the crystal’s length and the coherence time of the pump.We verify the possibility to improve the visibility using a purification protocol based on a compensation crystal