Optimal Control of a Sagnac Tractor Atom Interferometer

Atom interferometers are powerful tools for the precise measurement of gravitational fields, acceleration, and rotation, with numerous applications in fundamental physics, metrology, and inertial sensing. Rotation can be measured with unprecedented sensitivity from the Sagnac phase arising between wavepackets counter-rotating around an enclosed area. We consider here the implementation of a rotating tractor atom interferometer based on uninterrupted three-dimensional confinement and guidance. Ideally, the wavepacket components adiabatically follow pre-programmed trapping potentials. Minimizing the amplitude of the trapping potential reduces harmful photon scattering, while maximizing the average acceleration during splitting and recombination maximizes interferometric area for improved phase accumulation. However, weak trapping potentials and fast separation challenge adiabatic wavepacket evolution, and ultimately lead to a breakdown in fidelity. In the work presented here, we numerically map out the achievable fidelity versus trap depth and separation time. We show how the use of optimal control theory can counteract nonadiabatic defects. By dynamically tuning both amplitude and rotational acceleration of the trapping potentials during splitting and recombination, we can operate the rotating tractor interferometer at a limit of low power and yet high speed, leading to high fidelity under challenging conditions.