Mode expansion and Bragg filtering enable a high-fidelity fiber-based photon-pair source

TL;DR

This paper presents a fiber-based photon-pair source with enhanced efficiency and spectral brightness, achieved through mode expansion and Bragg filtering, enabling high purity and entanglement fidelity without background subtraction.

Contribution

The authors introduce a novel fiber-end expansion and Bragg filtering technique that significantly improves photon-pair extraction efficiency and spectral brightness in fiber-based sources.

Findings

Achieved a spectral brightness of 44,700 pairs/(s nm mW).

Produced photon-pairs with a second-order correlation function of 0.03.

Generated entangled photon-pairs with 97% fidelity and 92% tangle.

Abstract

We report the development of a fiber-based single spatial mode source of photon-pairs where the efficiency of extracting photon-pairs is improved over a previous source [18] through the use of fiber-end expansion and Bragg filters. This improvement in efficiency enabled a spectrally bright and pure photon-pair source having a small second-order correlation function (0.03) and a raw spectral brightness of 44,700 pairs/(s nm mW). The source can be configured to generate entangled photon-pairs,characterized via optimal and minimal quantum state tomography, to have a fidelity of 97% and tangle of 92%, without subtracting any background.