Angular spectrum influence and entanglement characterization of Gaussian-path encoded photonic qudits

Abstract

Entangled quantum states play an important role in quantum information science and also in quantum mechanics fundamental investigations. Implementation and characterization of techniques allowing for easy preparation of entangled states are important steps in such fields. Here we generated entangled quantum states encoded in photons’ transverse paths, obtained by pumping a nonlinear crystal with multiple transversal Gaussian beams. This approach allows us to generate entangled states of two qubits and two qutrits encoded in a Gaussian transversal path of twin photons. We make a theoretical analysis of this source, considering the influence of the pump angular spectrum on the generated states, further characterizing those by their purity and entanglement degree. Our experimental results reveal that the generated states present both high purity and entanglement, and the theoretical analysis elucidates how the pump beams profile can be used to manipulate such photonic states.