Security of device-independent quantum key distribution via monogamy relations from multipartite information causality

TL;DR

This paper shows that multipartite information causality (IC) principles can ensure device-independent quantum key distribution (QKD) security by establishing monogamy of Bell violations, unlike bipartite IC which fails to do so.

Contribution

It demonstrates that multipartite IC implies monogamy relations necessary for DIQKD security, highlighting the importance of a multipartite framework over bipartite formulations.

Findings

Multipartite IC implies monogamy of Bell violations.

Bipartite IC does not imply monogamy relations.

Security proven against individual attacks with quantum-attainable parameters.

Abstract

Beyond the foundational significance, the problem of bounding nonlocal correlations by reasonable physical principles has meaningful practical consequences, particularly for device-independent (DI) cryptographic security. In this work, we advance in this direction, demonstrating that the IC is enough to ensure DI security on quantum key distribution (QKD) protocols. Security is proven for a range of theoretically quantum-attainable parameters against individual attacks by a potentially post-quantum eavesdropper. This result follows as a consequence of a strong form of monogamy of Bell's inequality violations, which we have proven to be implied by the recently proposed multipartite formulation for IC. Additionally, we demonstrated that the original bipartite formulation of IC fails to imply monogamy relations and hence, ensure security of DIQKD, thus stressing the necessity of the multipartite framework.