  Quantum Monte Carlo and quantum simulation are both important tools for
understanding quantum many-body systems. As a classical algorithm, quantum
Monte Carlo suffers from the sign problem, preventing its application to most
fermion systems and real time dynamics. In this paper, we introduce a novel
non-variational algorithm using quantum simulation as a subroutine to
accelerate quantum Monte Carlo by easing the sign problem. The quantum
subroutine can be implemented with shallow circuits and, by incorporating error
mitigation, can reduce the Monte Carlo variance by several orders of magnitude
even when the circuit noise is significant. As such, the proposed quantum
algorithm is applicable to near-term noisy quantum hardware.
