CM-AMO Seminar | Optimal Control for Atom Interferometry and High-Precision Measurements

Atomic Fountain Interferometry (AFI) is a disruptive technology for the measurement of gravitational gradients and accelerations with remarkable precision. AFI is based on the manipulation of atom cloud in a free-fall-tower using laser pulses to create a superposition of two momentum space pathways. The interferometric signal contrast is limited by variations in the initial velocity of the atoms in the cloud and variations in the laser amplitude over the cross-section of the cloud. A robust pulse scheme must provide separation, mirroring, and recombination of the atoms to high precision over a realistic range of these variations. In our work we apply optimal control theory to design suitable pulse sequences to improve the efficiency of the AFI device. Our methodology relies on the simulation of the interferometer's full quantum dynamics. We test the efficacy of the proposed pulse schemes using adiabatic passage with frequency-chirped pulses and explore numerical optimal control theory to generate robust pulse schemes and formulate the most general control conditions for the implementation of an interferometer.

Applying optimal control theory for the efficient generation of N-atom non-classical states and their use for atom interferometry and quantum metrology are also discussed. As an example, we design a novel pulse sequence that drives an ensemble of cold trapped atoms into an optimal squeezed state. These states have a fundamental precision scaling proportional to the inverse of the number of atoms, known as the Heisenberg limit.