  The Robust Phase Estimation (RPE) protocol was designed to be an efficient
and robust way to calibrate quantum operations. The robustness of RPE refers to
its ability to estimate a single parameter, usually gate amplitude, even when
other parameters are poorly calibrated or when the gate experiences significant
errors. Here we demonstrate the robustness of RPE to errors that affect
initialization, measurement, and gates. In each case, the error threshold at
which RPE begins to fail matches quantitatively with theoretical bounds. We
conclude that RPE is an effective and reliable tool for calibration of
one-qubit rotations and that it is particularly useful for automated
calibration routines and sensor tasks.

Quantum Physics;Atomic Physics