  We introduce a novel technique for enhancing the robustness of light-pulse
atom interferometers against the pulse infidelities that typically limit their
sensitivities. The technique uses quantum optimal control to favorably harness
the multipath interference of the stray trajectories produced by imperfect
atom-optics operations. We apply this method to a resonant atom interferometer
and achieve thousand-fold phase amplification, representing a fifty-fold
improvement over the performance observed without optimized control. Moreover,
we find that spurious interference can arise from the interplay of spontaneous
emission and many-pulse sequences and demonstrate optimization strategies to
mitigate this effect. Given the ubiquity of spontaneous emission in quantum
systems, these results may be valuable for improving the performance of a
diverse array of quantum sensors. We anticipate our findings will significantly
benefit the performance of matter-wave interferometers for a variety of
applications, including dark matter, dark energy, and gravitational wave
detection.
