  Transitions out of the ground space limit the performance of quantum
adiabatic algorithms, while hardware imperfections impose stringent limitations
on the circuit depth. We propose an adiabatic echo verification protocol which
mitigates both coherent and incoherent errors, arising from non-adiabatic
transitions and hardware noise, respectively. Quasi-adiabatically evolving
forward and backwards allows for an echo-verified measurement of any
observable. In addition to mitigating hardware noise, our method uses
positive-time dynamics only. Crucially, the estimator bias of the observable is
reduced when compared to standard adiabatic preparation, achieving up to a
quadratic improvement.
