  Calibration of quantum computing technologies is essential to the effective
utilization of their quantum resources. Specifically, the performance of
quantum annealers is likely to be significantly impaired by noise in their
programmable parameters, effectively misspecification of the computational
problem to be solved, often resulting in spurious suboptimal solutions. We
developed a strategy to determine and correct persistent, systematic biases
between the actual values of the programmable parameters and their
user-specified values. We applied the recalibration strategy to two D-Wave Two
quantum annealers, one at NASA Ames Research Center in Moffett Field,
California, and another at D-Wave Systems in Burnaby, Canada. We show that the
recalibration procedure not only reduces the magnitudes of the biases in the
programmable parameters but also enhances the performance of the device on a
set of random benchmark instances.
