  We initiate the study of multi-source extractors in the quantum world. In
this setting, our goal is to extract random bits from two independent weak
random sources, on which two quantum adversaries store a bounded amount of
information. Our main result is a two-source extractor secure against quantum
adversaries, with parameters closely matching the classical case and tight in
several instances. Moreover, the extractor is secure even if the adversaries
share entanglement. The construction is the Chor-Goldreich [CG88] two-source
inner product extractor and its multi-bit variant by Dodis et al. [DEOR04].
Previously, research in this area focused on the construction of seeded
extractors secure against quantum adversaries; the multi-source setting poses
new challenges, among which is the presence of entanglement that could
potentially break the independence of the sources.
