Imperceptible measurement deviations can fake high-dimensional entanglement

Abstract

Quantum entanglement is a central resource for emerging quantum technologies, but its experimental certification usually assumes that prescribed quantum measurements can be realized exactly. This assumption becomes increasingly restrictive in high-dimensional systems, where accurate measurement control is more challenging. Here, we show that arbitrarily small, adversarially tailored measurement deviations can lead to the false certification of high-dimensional entanglement in systems that are, in fact, separable, with the effect becoming increasingly severe as the dimension grows. We experimentally demonstrate this across a broad range of dimensions using classical photonic states encoded in the spatial degree of freedom. We report false certification of several tens of entangled dimensions in systems spanning up to 61 dimensions while exploiting measurement deviations as low as 0.23%. Our results reveal how imperceptible invasive attacks can critically compromise high-dimensional entanglement certification, motivating the development of new certification methods robust to bounded discrepancies between theory and experiment.

arXiv comment6 pages and 3 figures (+30 pages supplementary)