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Randomness extractors are an important building block for classical and quantum cryptography. However, for many applications it is crucial that the extractors are quantum-proof, i.e., that they work even in the presence of quantum adversaries. In general, quantum-proof extractors are poorly understood and we would like to argue that in the same way as Bell inequalities (multiprover games) and communication complexity, the setting of randomness extractors provides a operationally useful framework for studying the power and limitations of a quantum memory compared to a classical one. We start by recalling how to phrase the extractor property as a quadratic program with linear constraints. We then construct a semidefinite programming (SDP) relaxation for this program that is tight for some extractor constructions. Moreover, we show that this SDP relaxation is even sufficient to certify quantum-proof extractors. This gives a unifying approach to understand the stability properties of extractors against quantum adversaries. Finally, we analyze the limitations of this SDP relaxation.
@InProceedings{berta_et_al:LIPIcs.TQC.2015.73,
author = {Berta, Mario and Fawzi, Omar and Scholz, Volkher B.},
title = {{Semidefinite Programs for Randomness Extractors}},
booktitle = {10th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2015)},
pages = {73--91},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-939897-96-5},
ISSN = {1868-8969},
year = {2015},
volume = {44},
editor = {Beigi, Salman and K\"{o}nig, Robert},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TQC.2015.73},
URN = {urn:nbn:de:0030-drops-55507},
doi = {10.4230/LIPIcs.TQC.2015.73},
annote = {Keywords: Randomness Extractors, Quantum adversaries, Semidefinite programs}
}