Experimentally Certified Transmission of a Quantum Message through an Untrusted and Lossy Quantum Channel via Bell's Theorem

TL;DR

This paper introduces a device-independent protocol for certifying quantum message transmission over lossy, untrusted channels, including an experimental demonstration with current quantum photonic technology, enhancing secure quantum communication.

Contribution

It presents a novel certification protocol that accounts for losses and adversarial conditions, moving beyond traditional assumptions and enabling practical verification of quantum links.

Findings

Successful experimental implementation with polarization-entangled photons.

Robustness analysis shows protocol tolerates realistic losses and errors.

Provides a method to estimate the quality of transmitted quantum messages.

Abstract

Quantum transmission links are central elements in essentially all protocols involving the exchange of quantum messages. Emerging progress in quantum technologies involving such links needs to be accompanied by appropriate certification tools. In adversarial scenarios, a certification method can be vulnerable to attacks if too much trust is placed on the underlying system. Here, we propose a protocol in a device independent framework, which allows for the certification of practical quantum transmission links in scenarios where minimal assumptions are made about the functioning of the certification setup. In particular, we take unavoidable transmission losses into account by modeling the link as a completely-positive trace-decreasing map. We also, crucially, remove the assumption of independent and identically distributed samples, which is known to be incompatible with adversarial settings. Finally, in view of the use of the certified transmitted states for follow-up applications, our protocol moves beyond certification of the channel to allow us to estimate the quality of the transmitted quantum message itself. To illustrate the practical relevance and the feasibility of our protocol with currently available technology we provide an experimental implementation based on a state-of-the-art polarization entangled photon pair source in a Sagnac configuration and analyze its robustness for realistic losses and errors.