  We discuss a surprisingly simple scheme for accounting (and removal) of error
in observables determined from quantum algorithms. A correction to the value of
the observable is calculated by first measuring the observable with all error
sources active and subsequently measuring the observable with each error source
removed separately. We apply this scheme to the variational quantum
eigensolver, simulating the calculation of the ground state energy of
equilibrium H$_2$ and LiH in the presence of several noise sources, including
amplitude damping, dephasing, thermal noise, and correlated noise. We show that
this scheme provides a decrease in the needed quality of the qubits by up to
two orders of magnitude. In near-term quantum computers, where full
fault-tolerant error correction is too expensive, this scheme provides a route
to significantly more accurate calculation
