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QI: Fachverband Quanteninformation

QI 14: Quantum Entanglement III

QI 14.2: Vortrag

Dienstag, 11. März 2025, 14:30–14:45, HS IX

Making entanglement witnesses robust to measurement errors — •Elisa Monchietti and Otfried Gühne — Naturwissenschaftlich-Technische Fakultät, Universität Siegen, Walter-Flex-Straße 3, 57068 Siegen, Germany

In recent years, various methods have been developed to characterise entanglement, one of the most widely studied are so-called entanglement witness operators. These are observables with the property that if their expectation value is greater than a predetermined quantity C, we can then ensure that the state is entangled, or that it possesses the type of entanglement that this witness allows us to characterize. In real practice, however, the measurement process is not ideal, and despite sophisticated error mitigation techniques complete elimination of errors due to external factors is not possible. If we assume that the measuring devices are not perfectly aligned, we find states whose result when the entanglement witness is applied is greater than the mentioned constant C, but which do not have the type of entanglement we are looking for, i.e., we obtain false positives. Our general aim is to provide methods to characterise quantum correlations in a more realistic way, considering the role of imprecise measurements. To do so, we study potential correction terms, which can be used to counteract the effects of misalignment and imperfections of measurement devices. First we are going to consider a simple scenario of two qubits, to understand possible correction terms. After this, the idea is to study the multipartite case, to develop a framework for error-robust entanglement witnesses for multiqubit systems.

Keywords: Entanglement; Witnesses