Degrees of freedom (mechanics) 1 Femtosecond lasers 1 Laser beams 1 Lithium 1 Lithium Niobate Waveguide 1 Niobium compounds 1 Periodically poled 1 Periodically poled lithium niobate waveguides 1 Phase matching 1 Photon pairs 1 Photon pairs generations 1 Photons 1 Physical experiments 1 Quantum entanglement 1 Quantum protocols Single photons 1 Spectral tunability 1 Spontaneous parametric down-conversion 1 Waveguides 1 femtosecond laser 1 lithium niobate waveguide 1 photon pair 1 spontaneous parametric downconversion 1