Probing Ultra-Fast Dephasing via Entangled Photon Pairs

TL;DR

This paper uses Hong-Ou-Mandel interference with entangled photons to measure ultrafast dephasing times in a medium, achieving high sensitivity even with significant optical loss.

Contribution

It introduces a method to probe ultrafast dephasing using HOM interference, enabling measurement of 22 fs dephasing time with high visibility despite optical loss.

Findings

Measured 22 fs dephasing time using CW laser

Achieved HOM dip visibility of 92.3% under high loss

Validated the method with a rigorous theoretical model

Abstract

We demonstrate how the Hong-Ou-Mandel (HOM) interference with polarization-entangled photons can be used to probe ultrafast dephasing. We can infer the optical properties like the real and imaginary parts of the complex susceptibility of the medium from changes in the position and the shape of the HOM dip. From the shift of the HOM dip, we are able to measure 22 fs dephasing time using a continuous-wave (CW) laser even with optical loss > 97%, while the HOM dip visibility is maintained at 92.3~\% (which can be as high as 96.7%). The experimental observations, which are explained in terms of a rigorous theoretical model, demonstrate the utility of HOM interference in probing ultrafast dephasing.