We demonstrate the ultimate sensitivity allowed by quantum physics in the estimation of the time delay between two photons by measuring their interference at a beam-splitter through frequency-resolving sampling measurements. This sensitivity can be increased quadratically by decreasing the photonic temporal bandwidth even at values smaller than the time delay when standard two-photon interferometers become inoperable and without adapting the path of the reference photon, nor the need of time-resolving detectors with an unfeasible high resolution. Applications can range from more feasible imaging of nanostructures, including biological samples, and nanomaterial surfaces to quantum enhanced estimation based on frequency-resolved boson sampling in optical networks.
@article{arxiv.2112.12102,
title = {Ultimate quantum sensitivity in the estimation of the delay between two interfering photons through frequency-resolving sampling},
author = {Danilo Triggiani and Giorgos Psaroudis and Vincenzo Tamma},
journal= {arXiv preprint arXiv:2112.12102},
year = {2023}
}