PSPACE is provable by two provers in one round
Jin‐Yi Cai, Anne Condon, R.J. Lipton · 2002
It is shown that every language in PSPACE, or equivalently every language accepted by an unbounded round interactive proof system, has a one-round, two-prover interactive proof with exponentially small error probability. To obtain this result, the correctness of a simple but powerful method for parallelizing two-prover interactive proofs to reduce their error is proved.>