  Certifying the performance of quantum computers requires standardized tests.
We propose a simple energy estimation benchmark that is motivated from quantum
chemistry. With this benchmark we statistically characterize the noisy outcome
of the IBM Quantum System One in Ehningen, Germany. We find that the benchmark
results hardly correlate with the gate errors and readout errors reported for
the device. In a time-resolved analysis, we monitor the device over several
hours and find two-hour oscillations of the benchmark results, as well as
outliers, which we cannot explain from the reported device status. We then show
that the implemented measurement error mitigation techniques cannot resolve
these oscillations, which suggests that deviations from the theoretical
benchmark outcome statistics do not stem solely from the measurement noise of
the device.
