Time-Resolved Upconversion of Entangled Photon Pairs

TL;DR

This paper experimentally investigates the ultrafast upconversion of entangled photon pairs with controlled time delays, revealing nonclassical correlations and the effects of dispersion on the process.

Contribution

It provides the first detailed measurement of time-resolved upconversion rates of entangled photons, demonstrating ultrafast nonclassical correlations and the impact of dispersion.

Findings

Upconversion rate has a FWHM of 27.9 fs under controlled conditions.

Group delay dispersion broadens the upconversion temporal profile.

Experimental results agree with theoretical calculations.

Abstract

In the process of spontaneous parametric downconversion, photons from a pump field are converted to signal and idler photon pairs in a nonlinear crystal. The reversed process, or upconversion of these pairs back to single photons in a second crystal, is also possible. Here, we present experimental measurements of the upconversion rate with a controlled time delay introduced between the signal and idler photons. As a function of delay, this rate presents a full width at half maximum of 27.9 fs under our experimental conditions, and we further demonstrate that group delay dispersion of the photon pairs broadens this width. These observations are in close agreement with our calculations, thus demonstrating an ultrafast, nonclassical correlation between the signal and idler waves.