Quantum key distribution with entangled photons generated on-demand by a quantum dot

TL;DR

This paper demonstrates the practical use of a quantum dot to generate entangled photons for quantum key distribution over fiber and free-space links, advancing real-world quantum communication.

Contribution

It presents the first field demonstration of a quantum dot-based entangled photon source for quantum key distribution in real-world conditions.

Findings

Successful implementation of a modified Ekert protocol

Entangled photons transmitted over 250 meters fiber and free-space

Quantum-dot sources are viable for practical quantum communication

Abstract

Quantum key distribution---exchanging a random secret key relying on a quantum mechanical resource---is the core feature of secure quantum networks. Entanglement-based protocols offer additional layers of security and scale favorably with quantum repeaters, but the stringent requirements set on the photon source have made their use situational so far. Semiconductor-based quantum emitters are a promising solution in this scenario, ensuring on-demand generation of near-unity-fidelity entangled photons with record-low multi-photon emission, the latter feature countering some of the best eavesdropping attacks. Here we first employ a quantum dot to experimentally demonstrate a modified Ekert quantum key distribution protocol with two quantum channel approaches: both a 250 meter long single mode fiber and in free-space, connecting two buildings within the campus of Sapienza University in Rome. Our field study highlights that quantum-dot entangled-photon sources are ready to go beyond laboratory experiments, thus opening the way to real-life quantum communication.