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Theory and experimental measurements of the pump and the signal photon. The pump has a star sin- gularity structure generated with the superposition of light beams carrying orbital angular momentum of 0 and 1 ̄h values, and opposite-handedness circular polarization. The signal photon is measured with a lemon singularity structure when the idler photon is projected along the diagonal polarization.
We created a quantum source of photon pairs with polarization complex structures.
The entangle property in the orbital angular momentum and polarization degrees of freedom is exploited to map different topological classes of polarization singularities on the transverse structure of the signal photon by projecting a selected polarization state in the idler photon.
The photon pairs generation relies on the Spontaneous Parametric Down Conversion where the incoming photon has a complex structure that can be inherited to the down-converted photons.
This quantum light source would have potential applications in quantum technologies based on photon-photon interference, quantum communications, and metrology. The paper is available here.