Efficient multipartite entanglement purification with the entanglement link from a subspace

TL;DR

This paper introduces an efficient multipartite entanglement purification protocol that enhances yield by recycling entangled subsystems, using entanglement links from a subspace, for N-photon GHZ states.

Contribution

It proposes a novel recycling MEPP that improves efficiency by utilizing entanglement links from discarded subsystems, surpassing existing protocols.

Findings

Higher purification efficiency than conventional methods

Effective recycling of entangled subsystems from discarded instances

Enhanced yield of high-fidelity N-photon entangled states

Abstract

We present an efficient multipartite entanglement purification protocol (MEPP) for N-photon systems in a Greenberger-Horne-Zeilinger state with parity-check detectors. It contains two parts. One is the conventional MEPP with which the parties can obtain a high-fidelity N-photon ensemble directly, similar to the MEPP with controlled-not gates. The other is our recycling MEPP in which the entanglement link is used to produce some $N$-photon entangled systems from entangled N'-photon subsystems (2 \leq N'<N) coming from the instances which are just discarded in all existing conventional MEPPs. The entangled N'-photon subsystems are obtained efficiently by measuring the photons with potential bit-flip errors. With these two parts, the present MEPP has a higher efficiency than all other conventional MEPPs.