Extracting an entangled photon pair from collectively decohered pairs at a telecommunication wavelength

TL;DR

This paper demonstrates an entanglement extraction method for photon pairs at telecommunication wavelengths, recovering entanglement after collective decoherence in fiber channels, crucial for quantum communication.

Contribution

The study introduces an experimental scheme to extract entanglement from decohered photon pairs at telecom wavelengths, enhancing quantum communication robustness.

Findings

Successfully extracted entanglement with fidelity 0.73

Demonstrated entanglement recovery after collective phase damping

Used photons at 780 nm and 1551 nm for telecom compatibility

Abstract

We experimentally demonstrated entanglement extraction scheme by using photons at the telecommunication band for optical-fiber-based quantum communications. We generated two pairs of non-degenerate polarization entangled photons at 780~nm and 1551~nm by spontaneous parametric down-conversion and distributed the two photons at 1551~nm through a collective phase damping channel which gives the same amount of random phase shift on the two photons. Through local operation and classical communication, we extracted an entangled photon pair from two phase-disturbed photon pairs. An observed fidelity of the extracted photon pair to a maximally entangled photon pair was 0.73 $\pm$ 0.07 which clearly shows the recovery of entanglement.