Sending photons (entangled or not) through optical fibres is a process prone to losses and noise. What happens to the quantum state undergoing such an adventure? Are the quantum states deteriorated in the process? If and when the state stops being quantum? Can we detect the non-classical characteristics of the state that has undergone significant attenuation? All this and many more questions answered. Just follow:

Efficiency vs. multi-photon contribution test for quantum dots
A. Predojević, M. Jezek, T. Huber, H. Jayakumar, T. Kauten, G. S. Solomon, R. Filip, and G. Weihs (Optics Express 22, 4789, 2014) - arXiv

Quantum non-Gaussian Depth of Single-Photon States
I. Straka, A. Predojević, T. Huber, L. Lachman, L. Butschek, M. Miková, M. Mičuda, G. S. Solomon, M. Ježek and G. Weihs (Phys. Rev. Lett. 113, 223603, 2014) - arXiv