  We propose a simple protocol for the verification of quantum computation
after the computation has been performed. Our construction can be seen as an
improvement on previous results in that it requires only a single prover, who
is restricted to measuring qubits in the $X$ or $Z$ basis, while requiring only
one way communication, from the prover to the verifier. We also show similar
constant round protocols with purely classical verifiers are not possible,
unless BQP is contained in the third level of the polynomial hierarchy.

Quantum Physics