|Title||Quantum Merlin Arthur with Exponentially Small Gap|
|Publication Type||Journal Article|
|Year of Publication||2016|
|Authors||Fefferman, B, Lin, CYen-Yu|
We study the complexity of QMA proof systems with inverse exponentially small promise gap. We show that this class can be exactly characterized by PSPACE, the class of problems solvable with a polynomial amount of memory. As applications we show that a "precise" version of the Local Hamiltonian problem is PSPACE-complete, and give a provable setting in which the ability to prepare PEPS states is not as powerful as the ability to prepare the ground state of general Local Hamiltonians.