Benchmarking quantum key distribution by mixing single photons and laser light

TL;DR

This paper presents a hybrid quantum key distribution approach using a mixture of single photons and laser pulses, demonstrating theoretical and experimental insights into efficiency and security advantages.

Contribution

It introduces a novel hybrid encoding scheme combining single photons and laser light for BB84, with a detailed phenomenological analysis and experimental validation.

Findings

Nearly perfect match between theory and experiment

Identification of an efficiency threshold for single-photon advantage

Insights into the role of single-photon purity and brightness

Abstract

Quantum key distribution is a key application of quantum mechanics, shaping the future of privacy and secure communications. Many protocols require single photons, often approximated by strongly attenuated laser pulses. Here, we harness the emission of a quantum dot embedded in a micropillar and explore a hybrid approach where the information is encoded on a mixture of single photons and laser pulses. We derive a phenomenological analysis of the configuration where both sources of light are mixed incoherently to perform the BB84 protocol, showing nearly perfect matching between theory and experiment. This provides a flexible technology compensating limited collected brightnesses of single-photon sources as well as a thorough investigation of single-photon statistics advantage scenarios over Poisson-distributed statistics. Explicitly, our model highlights an efficiency threshold for unconditional advantage of single photons over laser along with insights on the interplay between single-photon purity and collected brightness in the performances of BB84.