Parameter estimation of time and frequency shifts with generalized HOM interferometry

TL;DR

This paper explores how engineering the spectral properties of biphoton states can enhance the precision of time and frequency shift estimations in Hong-Ou-Mandel interferometry, with potential applications in biology and materials science.

Contribution

It introduces non-Gaussian biphoton states, especially grid states, as a means to significantly improve measurement precision in quantum interferometry.

Findings

Grid states outperform standard biphoton states in sensing accuracy.

Feasible production of these states with current photonic technologies.

Spectral engineering enhances the metrological power of HOM interferometers.

Abstract

Hong-Ou-Mandel interferometry takes advantage of the quantum nature of two-photon interference to increase the resolution of precision measurements of time-delays. Relying on few-photon probe states, this approach is applicable also in cases of extremely sensible samples and it achieves attosecond (nanometer path length) scale resolution, which is relevant to cell biology and two-dimensional materials. Here, we theoretically analyze how the precision of Hong-Ou-Mandel interferometers can be significantly improved by engineering the spectral distribution of two-photon probe states. In particular, we assess the metrological power of different classes of biphoton states with non-Gaussian time-frequency spectral distributions, considering the estimation of both time- and frequency-shifts. We find that grid states, characterized by a periodic structure of peaks in the chronocyclic Wigner function, can outperform standard biphoton states in sensing applications. The considered states can be feasibly produced with atomic photon sources, bulk non-linear crystals and integrated photonic waveguide devices.