Summary: QMA/qpoly # PSPACE/poly: DeMerlinizing Quantum Protocols
Scott Aaronson #
University of Waterloo
This paper introduces a new technique for removing ex
istential quantifiers over quantum states. Using this tech
nique, we show that there is no way to pack an exponential
number of bits into a polynomialsize quantum state, in such
a way that the value of any one of those bits can later be
proven with the help of a polynomialsize quantum witness.
We also show that any problem in QMA with polynomial
size quantum advice, is also in PSPACE with polynomial
size classical advice. This builds on our earlier result that
BQP/qpoly # PP/poly, and offers an intriguing counter
point to the recent discovery of Raz that QIP/qpoly = ALL.
Finally, we show that QCMA/qpoly # PP/poly and that
QMA/rpoly = QMA/poly.
Let Bob be a graduate student, and let x be an nbit string
representing his thesis problem. Bob's goal is to learn