On Entanglement Assisted Classical Optical Communications

Entanglement assisted communication is advocated by numerous authors as an alternative to classical communication offering significant improvement in channel capacity, in particular in noisy regime. In all those papers it is always assumed that entanglement can be distributed without any imperfections, except for attenuation. We demonstrate that under imperfect pre-shared entanglement distribution, assuming that entanglement distribution channel is modeled as a noisy and lossy Bosonic channel, the entanglement assisted communication can be inferior compared to the classical communication, depending on the parameters of the distribution channel. We identify the conditions under which entanglement assistance can still provide an advantage over the classical case. In particular, when both communication and entanglement distribution channels are not used for entanglement assisted communication but rather for classical transmission instead then the classical capacity is always higher than the entanglement assisted capacity. We also study the entanglement assisted communication under the strong atmospheric turbulence effects.