Joint Spectral Characterization of Photon-Pair Sources

TL;DR

This paper compares six techniques for characterizing the joint spectral properties of photon pairs generated by SPDC and SFWM, crucial for quantum photonics applications, analyzing their performance and suitability.

Contribution

It provides a comprehensive comparison of six different spectral characterization methods for photon-pair sources, highlighting their advantages and limitations.

Findings

Fourier transform spectroscopy offers resource-efficient spectral information.

Stimulated-emission measurement provides high accuracy in purity estimation.

Hong-Ou-Mandel interferometry effectively assesses indistinguishability.

Abstract

The ability to determine the joint spectral properties of photon pairs produced by the processes of spontaneous parametric downconversion (SPDC) and spontaneous four wave mixing (SFWM) is crucial for guaranteeing the usability of heralded single photons and polarization-entangled pairs for multi-photon protocols. In this paper, we compare six different techniques that yield either a characterization of the joint spectral intensity or of the closely-related purity of heralded single photons. These six techniques include: i) scanning monochromator measurements, ii) a variant of Fourier transform spectroscopy designed to extract the desired information exploiting a resource-optimized technique, iii) dispersive fibre spectroscopy, iv) stimulated-emission-based measurement, v) measurement of the second-order correlation function $g^{(2)}$ for one of the two photons, and vi) two-source Hong-Ou-Mandel interferometry. We discuss the relative performance of these techniques for the specific cases of a SPDC source designed to be factorable and SFWM sources of varying purity, and compare the techniques' relative advantages and disadvantages.