Measurement of ultrashort bi-photon correlation times with an integrated two-colour broadband SU(1,1)-interferometer

TL;DR

This paper demonstrates the measurement of ultrashort bi-photon correlation times around 100 fs using an integrated broadband SU(1,1) interferometer, advancing quantum spectroscopy and understanding dispersion effects.

Contribution

It introduces a method to measure ultrashort bi-photon correlation times with an integrated broadband SU(1,1) interferometer, combining spectral and temporal interferometry.

Findings

Measured bi-photon correlation times of ~100 fs.

Achieved simultaneous spectral and temporal interferograms.

Showed the impact of dispersion on bi-photon states.

Abstract

The bi-photon correlation time, a measure for the conditional uncertainty in the temporal arrival of two photons from a photon pair source, is a key performance identifier for many quantum spectroscopy applications, with shorter correlation times typically yielding better performance. Furthermore, it provides fundamental insight into the effects of dispersion on the bi-photon state. Here, we retrieve ultrashort bi-photon correlation times of around $100\,\mathrm{fs}$ by measuring simultaneously spectral and temporal interferograms at the output of an SU(1,1) interferometer based on an integrated broadband parametric down-conversion source in a $\mathrm{Ti:LiNbO}_3$ waveguide