Entanglement Distribution over Two-Sided Noisy Quantum Channels

We theoretically investigate the entanglement distribution process where both subsystems of the bipartite entangled state undergo noisy evolutions described by quantum channels. After the noisy evolutions, we assume that the two participating parties can perform local operations and classical communication to distill high-fidelity maximally entangled states from the noisy output of the quantum channels. In our work, we will focus on two particular cases where both channels are dephasing channels and where both channels are amplitude-damping channels. In both cases, we begin with the simpler regime where each channel is used twice and study the best achievable fidelity. Then we move on to the asymptotic regime, where each channel is used infinitely many times, and study the asymptotic rate at which maximally entangled states can be established per channel use. In both regimes, we find the interesting phenomenon that using an initial state that is entangled across different channel uses is more advantageous than using independent copies of maximally entangled states.