Implementation of a hybrid scheme for coherent plug-and-play quantum key distribution

TL;DR

This paper demonstrates a practical hybrid quantum key distribution system combining Distributed Phase Reference and Plug & Play protocols, enhancing simplicity, polarization insensitivity, and operational practicality in secure quantum communication.

Contribution

It introduces a novel hybrid configuration for QKD that integrates the advantages of multiple protocols within a server-client setup for real-world applications.

Findings

Successful experimental implementation of the hybrid scheme

Enhanced polarization insensitivity and self-referencing features

Practical key distribution with integrated detection and eavesdropping monitoring

Abstract

We experimentally demonstrate a hybrid configuration for Quantum Key Distribution, that combines the simplicity of Distributed Phase Reference protocols with the self-referencing features and polarization insensitivity of the so-called Plug & Play system. Additionally, all the components are arranged in a server-client scheme to allow for practical key distribution. Blank, coherent pulse pair trains are generated at the reception end of the link by means of a pulse sequence and an unbalanced interferometer, and sent to the other end. The emitter writes the qubits by erasing one of the pulses from the pair as in a Coherent-One Way protocol. Detection, as well as eavesdropping monitoring is performed at the receiver side, using the same interferometer that was used to generate the initial phase-referenced pulses.