Certifying semi-device-independent security via wave-particle duality experiments

TL;DR

This paper links wave-particle duality to semi-device-independent security, enabling certification of non-classicality and secure key rates through interferometric measurements, supported by a proof-of-principle experiment with quantum light.

Contribution

It introduces a novel connection between wave-particle duality and SDI security, expressing security witnesses in terms of interferometric quantities and validating them experimentally.

Findings

Classical bounds are violated in certain wave-particle experiments.

Security conditions can be certified directly from visibility and distinguishability.

An improved security bound enlarges the parameter space for secure quantum communication.

Abstract

Wave-particle duality is known to be equivalent to an entropic uncertainty relation based on the min- and max-entropies, which have a clear operational meaning in quantum cryptography. Here, we derive a connection between wave-particle relations and the semi-device-independent (SDI) security framework. In particular, we express an SDI witness entirely in terms of two complementary interferometric quantities: visibility and input distinguishability. Applying a symmetry condition to the interferometric quantities, we identify a scenario in which the classical bound is violated and the security condition is met in wave-particle experiments with a tunable beam splitter. This enables the certification of non-classicality and the positivity of the key rate directly from complementary interferometric quantities. Moreover, we perform a proof-of-principle experiment using orbital-angular-momentum encoded quantum states of light in a tunable interferometer, validating our theoretical predictions. Finally, we analyze an improved bound on the SDI security condition, effectively enlarging the parameter region where secure communication can be certified.