Experimental observation of impossible-to-beat quantum advantage on a hybrid photonic system

TL;DR

This paper reports the experimental demonstration of a quantum advantage in a four-dimensional photonic system that cannot be surpassed even with hypothetical postquantum resources, highlighting fundamental limits of quantum performance.

Contribution

The authors experimentally observe an impossible-to-beat quantum advantage in a high-dimensional photonic system, providing evidence of fundamental quantum limits using graph theory insights.

Findings

Quantum advantage observed in a four-dimensional system

Advantage matches the maximum allowed by postquantum theories

Experimental results align with theoretical predictions of quantum limits

Abstract

Quantum resources outperform classical ones for certain communication and computational tasks. Remarkably, in some cases, the quantum advantage cannot be improved using hypothetical postquantum resources. A class of tasks with this property can be singled out using graph theory. Here we report the experimental observation of an impossible-to-beat quantum advantage on a four-dimensional quantum system defined by the polarization and orbital angular momentum of a single photon. The results show pristine evidence of the quantum advantage and are compatible with the maximum advantage allowed using postquantum resources.