Efficient two-step entanglement concentration for arbitrary W states

TL;DR

This paper introduces two practical two-step entanglement concentration protocols for transforming arbitrary three-particle less-entangled W states into maximally entangled states, using linear optics and cross-Kerr nonlinearity, respectively.

Contribution

It presents novel, experimentally feasible protocols for entanglement concentration of W states, including a repeatable method with higher success probability using cross-Kerr nonlinearity.

Findings

First protocol achieves entanglement concentration with a certain success probability.

Second protocol does not require sophisticated detectors and can be repeated for higher success.

Both protocols are practical for quantum information applications.

Abstract

We present two two-step practical entanglement concentration protocols (ECPs) for concentrating an arbitrary three-particle less-entangled W state into a maximally entangled W state assisted with single photons. The first protocol uses the linear optics and the second protocol adopts the cross-Kerr nonlinearity to perform the protocol. In the first protocol, based on the post-selection principle, three parties say Alice, Bob and Charlie in different distant locations can obtain the maximally entangled W state from the arbitrary less-entangled W state with a certain success probability. In the second protocol, it dose not require the parties to posses the sophisticated single-photon detectors and the concentrated photon pair can be retained after performing this protocol successfully. Moreover, the second protocol can be repeated to get a higher success probability. Both protocols may be useful in practical quantum information applications.