Optimal nonlocal multipartite entanglement concentration based on projection measurements

TL;DR

This paper introduces an optimal nonlocal entanglement concentration protocol for multi-photon systems that maximizes success probability by using projection measurements, improving entanglement resources in quantum communication.

Contribution

It presents a novel entanglement concentration protocol that achieves maximal success probability through iterative projection measurements, enhancing multi-photon entanglement efficiency.

Findings

Achieves maximal success probability equal to the entanglement of the initial state.

Provides a method to obtain maximally entangled multi-photon states.

Enables iterative entanglement concentration for resource optimization.

Abstract

We propose an optimal nonlocal entanglement concentration protocol (ECP) for multi-photon systems in a partially entangled pure state, resorting to the projection measurement on an additional photon. One party in quantum communication first performs a parity-check measurement on her photon in an N-photon system and an additional photon, and then she projects the additional photon into an orthogonal Hilbert space for dividing the original $N$-photon systems into two groups. In the first group, the N parties will obtain a subset of $N$-photon systems in a maximally entangled state. In the second group, they will obtain some less-entangled N-photon systems which are the resource for the entanglement concentration in the next round. By iterating the entanglement concentration process several times, the present ECP has the maximal success probability which is just equivalent to the entanglement of the partially entangled state. That is, this ECP is an optimal one.