**Quantum collision-resistance of non-uniformly distributed functions** (QCrypt 2015)

Ehsan Ebrahimi Targhi, Gelo Noel Tabia, Dominique Unruh

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We study the quantum query complexity of finding a collision for a function $f$ whose outputs are chosen according to a distribution with min-entropy $k$. We prove that $Ω(2^{k/9})$ quantum queries are necessary to find a collision for function f.