  We show that the class QMA does not change even if we restrict Arthur's
computing ability to only Clifford gate operations (plus classical XOR gate).
The idea is to use the fact that the preparation of certain single-qubit
states, so called magic states, plus any Clifford gate operations are universal
for quantum computing. If Merlin is honest, he sends the witness plus magic
states to Arthur. If Merlin is malicious, he might send other states to Arthur,
but Arthur can verify the correctness of magic states by himself. We also
generalize the result to QIP[3]: we show that the class QIP[3] does not change
even if the computational power of the verifier is restricted to only Clifford
gate operations (plus classical XOR gate).
