We propose an interferometric scheme for the estimation of a linear combination with non-negative weights of an arbitrary number M>1 of unknown phase delays, distributed across an M-channel linear optical network, with Heisenberg-limited sensitivity. This is achieved without the need of any sources of photon-number or entangled states, photon-number resolving detectors or auxiliary interferometric channels. Indeed, the proposed protocol remarkably relys upon a single squeezed state source, an antisqueezing operation at the interferometer output, and on-off photodetectors.
@article{arxiv.1906.12294,
title = {Distributed Quantum Metrology with a Single Squeezed-Vacuum Source},
author = {Dario Gatto and Paolo Facchi and Frank Narducci and Vincenzo Tamma},
journal= {arXiv preprint arXiv:1906.12294},
year = {2019}
}