Multi-Photon Interference and Metrology

TL;DR

This paper examines how photon distinguishability impacts phase sensitivity in multi-photon interferometry, revealing that distinguishability negates sub-shot-noise advantages in certain linear optics schemes.

Contribution

It demonstrates that photon distinguishability reduces the phase sensitivity benefits of multi-photon interference in a specific interferometric setup.

Findings

Distinguishable photons yield similar phase sensitivity as identical photons for small phases.

Multiphoton interference does not achieve sub-shot-noise sensitivity for large photon numbers in the studied scheme.

Photon distinguishability impacts the quantum advantage in phase estimation.

Abstract

Recently, Motes et al. proposed in Phys. Rev. Lett. 114, 170802 (2015) a linear optics interferometer with N identical single photon input states as a tool for sub-shot-noise phase estimation which does not require NOON states sources. This thesis investigates how the degree of distinguishability between the input photonic spectra affects the interferometric phase sensitivity, by employing the results obtained by Tamma and Laibacher in Phys. Rev. Lett. 114, 243601 (2015). Remarkably, the obtained results show, that for small phases, the phase sensitivity in the case of completely distinguishable photons is identical to the one in the case of identical photons considered by Motes et al. apart from a constant factor that is independent of the number N of input photons. Consequently, multiphoton interference does not provide in the scheme proposed by Motes et al. any sub-shot-noise sensitivity for a large number N of photons.