Single-photon-assisted entanglement concentration of a multi-photon system in a partially entangled W state with weak cross-Kerr nonlinearity

TL;DR

This paper introduces a nonlocal entanglement concentration protocol for multi-photon W states using single photons and cross-Kerr nonlinearity, achieving high success probability with practical advantages for quantum communication.

Contribution

It presents a novel entanglement concentration method that does not require two copies of the system, improving feasibility and success rate in quantum communication.

Findings

Success probability approaches the theoretical limit with multiple iterations.

Requires only the N-photon system and ancillary single photons, simplifying implementation.

High success probability compared to previous protocols.

Abstract

We propose a nonlocal entanglement concentration protocol (ECP) for $N$-photon systems in a partially entangled W state, resorting to some ancillary single photons and the parity-check measurement based on cross-Kerr nonlinearity. One party in quantum communication first performs a parity-check measurement on her photon in an $N$-photon system and an ancillary photon, and then she picks up the even-parity instance for obtaining the standard W state. When she obtains an odd-parity instance, the system is in a less-entanglement state and it is the resource in the next round of entanglement concentration. By iterating the entanglement concentration process several times, the present ECP has the total success probability approaching to the limit in theory. The present ECP has the advantage of a high success probability. Moreover, the present ECP requires only the $N$-photon system itself and some ancillary single photons, not two copies of the systems, which decreases the difficulty of its implementation largely in experiment. It maybe have good applications in quantum communication in future.