Distilling and protecting the single-photon entangled state

TL;DR

This paper introduces two efficient protocols for entanglement concentration of single-photon states that also preserve encoded quantum information, utilizing linear optics and nonlinearities for practical quantum communication improvements.

Contribution

The paper presents novel entanglement concentration protocols that can both maximize entanglement and protect quantum information, using minimal resources and adaptable to current technology.

Findings

First protocol uses linear optics, feasible with current technology.

Second protocol employs cross-Kerr nonlinearities, allowing repeated concentration.

High success probability achieved through iterative use of the second protocol.

Abstract

We propose two efficient entanglement concentration protocols (ECPs) for arbitrary less-entangled single-photon entanglement (SPE). Different from all the previous ECPs, these protocols not only can obtain the maximally SPE, but also can protect the single qubit information encoded in the polarization degree of freedom. These protocols only require one pair of less-entangled single-photon entangled state and some auxiliary single photons, which makes them economical. The first ECP is operated with the linear optical elements, which can be realized in current experiment. The second ECP adopts the cross-Kerr nonlinearities. Moreover, the second ECP can be repeated to concentrate the discard states in some conventional ECPs, so that it can get a high success probability. Based on above properties, our ECPs may be useful in current and future quantum communication.