Theory of Computing ------------------- Title : Classical Verification of Quantum Proofs Authors : Zhengfeng Ji Volume : 15 Number : 5 Pages : 1-42 URL : https://theoryofcomputing.org/articles/v015a005 Abstract -------- We present a classical interactive protocol that checks the validity of a quantum witness state for the local Hamiltonian problem. It follows from this protocol that approximating the nonlocal value of a multi-player one-round game to inverse polynomial precision is QMA-hard. Our result makes a connection between the theory of QMA-completeness and Hamiltonian complexity on one hand and the study of nonlocal games and Bell inequalities on the other. ---------------- An extended abstract of this paper appeared in the Proceedings of the 48th annual ACM Symposium on Theory of Computing (STOC'16).