Abstract
We study a variant of QMA where quantum proofs have non-negative amplitudes in both completeness and soundness. This class was introduced by Jeronimo and Wu [STOC '23] to understand QMA(2). We show that this variant is very powerful even without considering multiple unentangled quantum provers. In fact, QMA+ with some constant gap is equal to NEXP, even though QMA+ with some other constant gap is equal to QMA.