Spectroscopy of Rydberg Atoms in Optical Lattices and Laser Traps

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

Physicists at the University of Michigan are useing "ponderomotive spectroscopy," an advanced form of a technique that traces back at least to the 17th century when Isaac Newton first showed that white light sent through a prism breaks into a rainbow. The new high-resolution spectroscopy allows the researchers to peer more deeply into the structure of atoms and direct their behavior at a much finer scale. The measurements made possible by ponderomotive spectroscopy could thus lead to advances in fundamental physics and promote the progress of science. In their research, the scientists use Rydberg atoms--giant atoms that exhibit not only greater size, but also stronger interactions than usual atoms. Rydberg atoms enable the new method of ponderomotive spectroscopy. In addition, they allow for the detection of small electromagnetic fields, which may improve our ability to measure natural or human activity, as well as investigate how systems of quantum-mechanical matter (matter that behaves like waves) interact with each other. In detail, the researchers employ a spectroscopic method in which highly excited Rydberg atoms are prepared in a modulated optical-lattice laser trap. Laser-cooled ground-state atoms are excited into Rydberg levels within the optical lattice. The lattice field holds on to the tenuously bound Rydberg electron via the ponderomotive light-electron interaction, which in turn results in a trapping force for the entire atom. Time-dependent microwave modulation of the trapping field then drives transitions between Rydberg-atom levels whose energies are separated by odd harmonics of the modulation frequency. The frequency-resolution and accuracy limits of lattice modulation spectroscopy are explored. The method is employed to measure atomic quantities, such as quantum defects, ionic polarizabilities and the Rydberg constant. Using a cavity-generated, very deep implementation of the Rydberg-atom lattice, the energies of strongly mixed Rydberg adiabatic states are measured. Other measurement objectives are the polarizabilities of low-lying atomic levels and light propagation in the densely filled cold-atom channels present in the cavity-generated optical lattice. In a second research component, the trajectories of Rydberg-atom pairs are measured using a direct atom imaging technique, which is based on Rydberg-atom field ionization, ion extraction and spatial imaging. The trajectory measurements reveal interatomic forces and their anisotropy. The Rydberg-atom interactions are controlled via adiabatic passage in Landau-Zener crossings in the Rydberg-atom Stark map, which allows the preparation of dense, highly dipolar quantum matter.