r of Unentanglement (Extended Abstract) Scott Aaronson MIT Salman Beigi MIT Andrew Drucker MIT Bill Fefferman University of Chicago Peter Shor MIT The class QMA (k), introduced by Kobayashi et al., consists of all languages that can be verified using k unentangled quantum proofs. Many of the simplest questions about this class have remained embarrassingly open: for example, can we give any evidence that k quantum proofs are more powerful than one? Can we show any upper bound on QMA (k), besides the trivial NEXP? Does QMA (k) = QMA (2) for k 2? Can QMA (k) protocols be amplified to exponentially small error? In this paper, we make progress on all of the above questions.