Thousandfold Phase Amplification in a Resonant Atom Interferometer via Applying Robust Quantum Control to Multipath Interference

Recent advances have opened a path for a new generation of light-pulse atom interferometers to pursue scientific goals such as searches for wave-like dark matter and gravitational wave detection in currently unexplored frequency ranges. A key challenge in these ambitious applications is to design interferometer sequences which are robust against pulse infidelities, which inevitably arise due to experimental tradeoffs and imperfections.

Resonant atom interferometers, which amplify the interferometer phase response to signals oscillating at a particular target frequency, have been proposed to boost the sensitivity of atomic dark matter, dark energy, and gravitational wave detectors. In this talk, I will discuss a novel type of robust resonant atom interferometer that applies quantum optimal control to multipath interference of many spatial trajectories to overcome limitations from pulse infidelities. This method allows us to demonstrate resonant phase amplification factors in excess of 1000, arising from the sequential application of in excess of 500 mirror pulses, even with individual pulse transfer efficiencies of only approximately 90%. By contrast, without optimized control, the interferometer fringe visibility rapidly decays as the number of mirror pulses is increased past 10. In this context, I will compare the results of various approaches to quantum optimal control.