Multi-photon QKD for Practical Quantum Networks

TL;DR

This paper explores multi-photon quantum key distribution protocols, especially the 3-stage protocol, to overcome limitations of single-photon sources and extend transmission distances in practical quantum networks.

Contribution

It compares the 3-stage QKD protocol with conventional methods and establishes a mathematical relationship to enhance key rates across different network topologies.

Findings

3-stage QKD tolerates multiple photons without leakage

Key rate relationships improve transmission distances

Protocol performance varies with network topology

Abstract

Quantum key distribution (QKD) will most likely be an integral part of any practical quantum network in the future. However, not all QKD protocols can be used in today's networks because of the lack of single-photon emitters and noisy intermediate quantum hardware. Attenuated-photon transmission, typically used to simulate single-photon emitters, severely limits the achievable transmission distances and makes the integration of the QKD into existing classical networks, that use tens of thousands of photons per bit of transmission, difficult. Furthermore, it has been found that protocol performance varies with topology. In order to remove the reliance of QKD on single-photon emitters and increase transmission distances, it is worthwhile to explore QKD protocols that do not rely on single-photon transmissions for security, such as the 3-stage QKD protocol, which can tolerate multiple photons in each burst without information leakage. This paper compares and contrasts the 3-stage QKD protocol with conventional QKD protocols and its efficiency in different network topologies and conditions. Furthermore, we establish a mathematical relationship between achievable key rates to increase transmission distances in various topologies.