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Timo Simnacher

Timo Simnacher PhD student

Room: B-111

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Publications

See also arxiv

Timo Simnacher, Nikolai Wyderka, René Schwonnek and Otfried Gühne
Entanglement detection with scrambled data
Phys. Rev. A 99, 062339 (2019), arXiv:1901.07946

In the usual entanglement detection scenario the possible measurements and the corresponding data are assumed to be fully characterized. We consider the situation where the measurements are known, but the data is scrambled, meaning the assignment of the probabilities to the measurement outcomes is unknown. We investigate in detail the two-qubit scenario with local measurements in two mutually unbiased bases. First, we discuss the use of entropies to detect entanglement from scrambled data, showing that Tsallis- and R\'enyi entropies can detect entanglement in our scenario, while the Shannon entropy cannot. Then, we introduce and discuss scrambling-invariant families of entanglement witnesses. Finally, we show that the set of non-detectable states in our scenario is non-convex and therefore in general hard to characterize.

Timo Simnacher, Nikolai Wyderka, Cornelia Spee, Xiao-Dong Yu and Otfried Gühne
Certifying quantum memories with coherence
Phys. Rev. A 99, 062319 (2019), arXiv:1809.03403

Quantum memories are an important building block for quantum information processing. Ideally, these memories preserve the quantum properties of the input. We present general criteria for measures to evaluate the quality of quantum memories. Then, we introduce a quality measure based on coherence satisfying these criteria, which we characterize in detail for the qubit case. The measure can be estimated from sparse experimental data and may be generalized to characterize other building blocks, such as quantum gates and teleportation schemes.