Estimating the photon-number distribution of photonic channels with realistic devices and applications in photonic quantum information processing

TL;DR

This paper introduces a method to estimate the photon-number distribution of unknown optical channels using standard devices, aiding quantum information tasks without requiring ideal photon-number-resolving detectors.

Contribution

It presents a rigorous approach to bound photon-number distributions with realistic devices, expanding practical quantum channel characterization capabilities.

Findings

Method successfully bounds photon-number distributions with standard devices

Application to quantum key distribution security analysis

Proposal for implementing photon counting with homodyne detectors

Abstract

Characterising the input-output photon-number distribution of an unknown optical quantum channel is an important task for many applications in quantum information processing. Ideally, this would require deterministic photon-number sources and photon-number-resolving detectors, but these technologies are still work-in-progress. In this work, we propose a general method to rigorously bound the input-output photon number distribution of an unknown optical channel using standard optical devices such as coherent light sources and non-photon-number-resolving detectors/homodyne detectors. To demonstrate the broad utility of our method, we consider the security analysis of practical quantum key distribution systems based on calibrated single-photon detectors and an experimental proposal to implement time-correlated single photon counting technology using homodyne detectors instead of single-photon detectors.