Multipartite entanglement to boost superadditivity of coherent information in quantum communication lines with polarization-dependent losses

Coherent information quantifies the achievable rate of reliable quantum transmission through a communication channel. Use correlated states instead factorized ones may result in an increase coherent information, phenomenon known as superadditivity. However, even for simple physical models channels it is rather difficult to detect superadditivity and find advantageous multipartite states. Here we consider case polarization dependent losses propose some physically motivated entangled which outperform all wide range channel parameters. We show that asymptotic limit infinite number uses takes place whenever neither degradable nor antidegradable. Besides identification, also provide method how modify proposed get higher by doubling uses. The obtained results give deeper understanding multishot scenario serve benchmark capacity estimations future approaches toward optimal strategy transfer information.