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QI: Fachverband Quanteninformation

QI 14: Quantum Entanglement III

QI 14.1: Hauptvortrag

Dienstag, 11. März 2025, 14:00–14:30, HS IX

Certification of high-dimensional and multipartite entanglement with imperfect measurements — •Simon Morelli¹, Hayata Yamasaki², Marcus Huber¹, and Armin Tavakoli³ — ¹Atominstitut, Technische Universität Wien, Austria — ²University of Tokyo, Japan — ³Lund University, Sweden

Deciding whether an unknown quantum state is entangled is a central challenge in quantum information. The most common approach are entanglement witnesses, where one assumes the state to be close to a known target and then finds suitable measurements that can reveal its entanglement. In principle, this allows for the detection of every entangled state. However, it requires the experimenter to flawlessly perform the stipulated measurements.

We move away from this idealized scenario to the more realistic situation in which measurement devices are not perfectly controlled, but operate with bounded inaccuracy. We formalize this through an operational notion of inaccuracy that can be estimated directly in the laboratory and investigate the impact of measurement errors on standard entanglement detection techniques. To demonstrate the relevance of this approach, we show that small magnitudes of inaccuracy can significantly compromise several renowned entanglement witnesses.

We extend this analysis to the detection of high-dimensional and multipartite entanglement. To support our theoretical findings experimentally, we explicitly construct states that lead to a wrongful detection of high Schmidt number or genuine multipartite entanglement when the inaccuracies in the measurements are not accounted for.

Keywords: entanglement detection; measurement inaccuracies; high-dimensional entanglement; multipartite entanglement; experimental certification