Towards joint reconstruction of noise and losses in quantum channels

TL;DR

This paper introduces a protocol using photon-number-resolving detectors at various efficiencies to simultaneously estimate transmission losses and noise photon statistics in quantum channels, demonstrated through experimental results.

Contribution

The paper presents a novel protocol that jointly reconstructs noise and losses in quantum channels using a single measurement approach.

Findings

Successful experimental implementation with different noise levels.

Accurate estimation of transmission losses and noise photon distribution.

Protocol outperforms traditional separate measurement methods.

Abstract

The calibration of a quantum channel, i.e. the determination of the transmission losses affecting it, is definitely one of the principal objectives in both the quantum communication and quantum metrology frameworks. Another task of the utmost relevance is the identification, e.g. by extracting its photon number distribution, of the noise potentially present in the channel. Here we present a protocol, based on the response of a photon-number-resolving detector at different quantum efficiencies, able to accomplish both of these tasks at once, providing with a single measurement an estimate of the transmission losses as well as the photon statistics of the noise present in the exploited quantum channel. We show and discuss the experimental results obtained in the practical implementation of such protocol, with different kinds and levels of noise.