Entanglement is a fundamental ingredient for extending quantum key distribution from two-party communication to networks without trusted nodes. Yet, the commercial application of this concept is currently hindered by the probabilistic nature of the photon-generation process underlying the used entanglement resources.

QD-E-QKD will develop a novel technology based on semiconductor quantum dots and test it in realistic urban communication scenarios to surpass the limits of current approaches to entanglement-based quantum key distribution.
Our photonic source will combine recent research developments in microfabrication in a single device. Its structural design will embed high-quality epitaxial quantum dots and include a p-i-n-i-n diode for the suppression of charge noise, a circular Bragg grating cavity for brightness enhancement, and a piezoelectric substrate for optimal entanglement. We predict that our device will operate—at near-unity degree of entanglement—at rates that are more than one order of magnitude higher that those accessible by state-ofthe-art parametric down converters for the same qubit error rate. At the same time, the near-zero multi-pair emission probability guarantees better robustness against channel attenuation losses in the communication protocol implementation.

We will use this device to implement quantum key distribution using two quantum-channel approaches, a single-mode fiber and free space. To guarantee stable operation we will develop a stand-alone device that combines time-to-digital conversion with optical clock recovery for remote synchronization and a free spaceoptical-communication receiver with integrated adaptive optics based on deformable lenses.

Finally, we will provide quantitative benchmarking, backed by theoretical modelling and testing, to certify the advancement over existing entanglement-based quantum key distribution systems. This will offer a viable technology for the realization of more complex quantum key distribution networks.

CONSORTIUM

• Coordinator: Rinaldo Trotta (Sapienza University of Rome, Physics Department, IT)
• Stefano Bonora (CNR / IFN Padova, IT)
• Tobias Huber (Julius Maximilians Universität Würzburg / Technische Physik, DE)
• Henning Weier (Quantum Technology Laboratories Deutschland GmbH, DE)
• Armando Rastelli (Johannes Kepler University / Institute of Semiconductor & Solid State Physics, AT)
• Thomas Scheidl (Quantum Technology Laboratories GmbH, AT)
• Vladyslav Usenko (Palacký University, Olomouc, Faculty of Science, CZ)

JKU PI: Armando Rastelli

Funding agency: FFG

Funding period: 01.06.2022-31.05.2025