08 Fakultät Mathematik und Physik
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/9
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Item Open Access Bell-state measurement exceeding 50% success probability with linear optics(2023) Bayerbach, Matthias J.; D’Aurelio, Simone E.; Loock, Peter van; Barz, StefanieItem Open Access Correlations for computation and computation for correlations(2021) Demirel, Bülent; Weng, Weikai; Thalacker, Christopher; Hoban, Matty; Barz, StefanieQuantum correlations are central to the foundations of quantum physics and form the basis of quantum technologies. Here, our goal is to connect quantum correlations and computation: using quantum correlations as a resource for computation - and vice versa, using computation to test quantum correlations. We derive Bell-type inequalities that test the capacity of quantum states for computing Boolean functions within a specific model of computation and experimentally investigate them using 4-photon Greenberger-Horne-Zeilinger (GHZ) states. Furthermore, we show how the resource states can be used to specifically compute Boolean functions - which can be used to test and verify the non-classicality of the underlying quantum states. The connection between quantum correlation and computability shown here has applications in quantum technologies, and is important for networked computing being performed by measurements on distributed multipartite quantum states.Item Open Access Experimental anonymous conference key agreement using linear cluster states(2023) Rückle, Lukas; Budde, Jakob; Jong, Jarn de; Hahn, Frederik; Pappa, Anna; Barz, StefanieItem Open Access Non-adaptive measurement-based quantum computation on IBM Q(2023) Mackeprang, Jelena; Bhatti, Daniel; Barz, StefanieWe test the quantumness of IBM’s quantum computer IBM Quantum System One in Ehningen, Germany. We generate generalised n -qubit GHZ states and measure Bell inequalities to investigate the n -party entanglement of the GHZ states. The implemented Bell inequalities are derived from non-adaptive measurement-based quantum computation (NMQC), a type of quantum computing that links the successful computation of a non-linear function to the violation of a multipartite Bell-inequality. The goal is to compute a multivariate Boolean function that clearly differentiates non-local correlations from local hidden variables (LHVs). Since it has been shown that LHVs can only compute linear functions, whereas quantum correlations are capable of outputting every possible Boolean function it thus serves as an indicator of multipartite entanglement. Here, we compute various non-linear functions with NMQC on IBM’s quantum computer IBM Quantum System One and thereby demonstrate that the presented method can be used to characterize quantum devices. We find a violation for a maximum of seven qubits and compare our results to an existing implementation of NMQC using photons.