Testing the photon-number statistics of a quantum key distribution light source

TL;DR

This paper introduces a correlation function measurement method to experimentally determine the photon-number statistics of a quantum light source, which is crucial for assessing security and performance in quantum key distribution systems.

Contribution

The paper presents a novel experimental technique to characterize photon statistics, aiding in the certification and security analysis of quantum communication devices.

Findings

Method effectively measures photon statistics

Improves estimation of quantum key distribution key rate

Supports certification of quantum light sources

Abstract

A commonly held tenet is that lasers well above threshold emit photons in a coherent state, which follow a Poissonian statistics when measured in photon number. This feature is often exploited to build quantum-based random number generators or to derive the secure key rate of quantum key distribution systems. Hence the photon number distribution of the light source can directly impact the randomness and the security distilled from such devices. Here, we propose a method based on measuring correlation functions to experimentally characterise a light source's photon statistics and use it in the estimation of a quantum key distribution system's key rate. This promises to be a useful tool for the certification of quantum-related technologies.