We present verification protocols to gain confidence in the correct
performance of the realization of an arbitrary universal quantum computation.
The derivation of the protocols is based on the fact that matchgate
computations, which are classically efficiently simulable, become universal if
supplemented with additional resources. We combine tools from weak simulation,
randomized compiling, and classical statistics to derive verification circuits.
These circuits have the property that (i) they strongly resemble the original
circuit and (ii) cannot only be classically efficiently simulated in the ideal,
i.e. error free, scenario, but also in the realistic situation where errors are
present. In fact, in one of the protocols we apply exactly the same circuit as
in the original computation, however, to a slightly modified input state.Comment: 17 pages, 8 figure