  We propose a quantum error mitigation strategy for the variational quantum
eigensolver (VQE) algorithm. We find, via numerical simulation, that very small
amounts of coherent noise in VQE can cause substantially large errors that are
difficult to suppress by conventional mitigation methods, and yet our proposed
mitigation strategy is able to significantly reduce these errors. The proposed
strategy is a combination of previously reported techniques, namely randomized
compiling (RC) and zero-noise extrapolation (ZNE). Intuitively, randomized
compiling turns coherent errors in the circuit into stochastic Pauli errors,
which facilitates extrapolation to the zero-noise limit when evaluating the
cost function. Our numerical simulation of VQE for small molecules shows that
the proposed strategy can mitigate energy errors induced by various types of
coherent noise by up to two orders of magnitude.
