Experimental implementation of secure anonymous protocols on an eight-user quantum key distribution network

• Published in: npj quantum information Vol. 8; no. 1; pp. 1 - 7
• Main Authors: Huang, Zixin, Joshi, Siddarth Koduru, Aktas, Djeylan, Lupo, Cosmo, Quintavalle, Armanda O., Venkatachalam, Natarajan, Wengerowsky, Sören, Lončarić, Martin, Neumann, Sebastian Philipp, Liu, Bo, Samec, Željko, Kling, Laurent, Stipčević, Mario, Ursin, Rupert, Rarity, John G.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 07.03.2022; Nature Publishing Group; Nature Portfolio
• Subjects: 639/624/400/482; 639/766/259; 639/766/400/482; 639/766/483/481; Classical and Quantum Gravitation; Communication; Cryptography; Parity; Physics; Physics and Astronomy; Privacy; Quantum Computing; Quantum Field Theories; Quantum Information Technology; Quantum Physics; Relativity Theory; Spintronics; String Theory
• ISSN: 2056-6387; 2056-6387
• DOI: 10.1038/s41534-022-00535-1

Anonymity in networked communication is vital for many privacy-preserving tasks. Secure key distribution alone is insufficient for high-security communications. Often, knowing who transmits a message to whom and when must also be kept hidden from an adversary. Here, we experimentally demonstrate five information-theoretically secure anonymity protocols on an eight user city-wide quantum network using polarisation entangled photon pairs. At the heart of these protocols is anonymous broadcasting, which is a cryptographic primitive that allows one user to reveal one bit of information while keeping their identity anonymous. For a network of n users, the protocols retain anonymity for the sender, given that no more than n  − 2 users are colluding. This is an implementation of genuine multi-user cryptographic protocols beyond standard QKD. Our anonymous protocols enhance the functionality of any fully-connected Quantum Key Distribution network without trusted nodes.