Linear optics-based entanglement concentration protocols for cluster-type entangled coherent state

Abstract

We proposed two linear optics-based entanglement concentration protocols (ECPs) to obtain maximally entangled 4-mode cluster-type entangled coherent state (ECS) from less (partially) entangled cluster-type ECS. The first ECP is designed using a superposition of single-mode coherent state with two unknown parameters, whereas the second ECP is obtained using a superposition of single-mode coherent state and a superposition of two-mode coherent state with four unknown parameters. The success probabilities have been calculated for both the ECPs. The necessary quantum circuits enabling future experimental realizations of the proposed ECPs are provided using linear optical elements. Further, the benefit of the proposed schemes is established in the context of long-distance quantum communication where photon loss is an obstruction.