Entanglement distribution via noisy quantum channels

Abstract

We investigate the change of entanglement for distributing an arbitrarily entangled two-qubit pure state via three typical kinds of noisy quantum channels—amplitude damping, phase damping and depolarizing quantum channels. We find that for one-qubit transmission, the output distant entanglement (measured by concurrence) reduces proportionately with respect to its initial amount, and the entanglement-decay ratio is determined only by the noisy characteristics of quantum channels. For two-qubit transmission, the rule of the entanglement change is complex. For phase damping quantum channels, the four Bell states and are all the optimal entanglement-distribution (OED) input states. But for amplitude damping quantum channels, only |ψ±⟩ are the OED input. For depolarizing quantum channels, and in the case of symmetrical quantum channels, the four Bell states are still the OED input. We also discuss the problem of entanglement sudden death (ESD) and find that for all the three types of quantum channels, ESD can be found.