Experimental demonstration of robust entanglement distribution over reciprocal noisy channels assisted by a counter-propagating classical reference light

TL;DR

This paper experimentally demonstrates a robust entanglement distribution scheme over reciprocal noisy channels using a classical reference light, achieving high sharing rates and preserving entanglement.

Contribution

It provides the first experimental validation of a scheme that enhances entanglement distribution robustness via reciprocal noisy channels with classical assistance.

Findings

Achieved entanglement sharing rate proportional to channel transmittance.

Maintained high entanglement quality after transmission.

Applicable to arbitrary polarization states of single photons.

Abstract

We experimentally demonstrate a proposal [Phys. Rev. A 87, 052325 (2013)] of a scheme for robust distribution of polarization entangled photon pairs over collective noisy channels having the reciprocity. Although the scheme employs the robustness of two qubit decoherence-free subspace, by utilizing the forward propagation of one half of the entangled photons and the backward propagation of a classical reference light, it achieves an entanglement-sharing rate proportional to the transmittance of the quantum channel for the signal photon. We experimentally observed the efficient sharing rate while keeping a highly entangled state after the transmission. We also show that the protection method is applicable to transmission of arbitrary polarization state of a single photon.