Systems of cold, interacting Rydberg atoms are of interest because they exhibit a wide range of collective quantum phenomena. This thesis describes experimental and theoretical work related to these systems with an emphasis on two phenomena: Rydberg excitation blockades and quantum-state-changing collisions. I begin by presenting a detailed calculation of the interaction energies of two Rydberg atoms for a variety of orientations, quantum states, and applied electric fields. The calculated energies are used to interpret the experimental results that follow. I then describe measurements showing that the widths of the distributions of Rydberg excitation number are related to the effectiveness of a Rydberg excitation blockade. These distributions are investigated as a function of principal quantum number, n, and applied electric field. In the presence of a Forster resonant field, sub-Poissonian distributions are measured. I next present a spectroscopic measurement of the energy level shift of a system of atoms which collectively shares two Rydberg excitations. The qualitative nature of the shift depends sensitively on the type of interactions between the atoms (van der Waals or dipole-dipole) and may be changed by changing the quantum state or applied electric field. This measurement provides the first spectroscopic proof that Rydberg excitation blockades are operative. Finally, I describe measurements of the probability for quantum state-changing and Penning-ionizing collisions to provide evidence for intrinsic, electric field-free-interaction resonances and complex many-body interactions in systems of cold Rydberg atoms.Systems of cold, interacting Rydberg atoms are of interest because they exhibit a wide range of collective quantum phenomena. This thesis describes experimental and theoretical work related to these systems with an emphasis on two phenomena: Rydberg excitation blockades and quantum-state-changing collisions. I begin by presenting a detailed calculation of the interaction energies of two Rydberg atoms for a variety of orientations, quantum states, and applied electric fields. The calculated energies are used to interpret the experimental results that follow. I then describe measurements showing that the widths of the distributions of Rydberg excitation number are related to the effectiveness of a Rydberg excitation blockade. These distributions are investigated as a function of principal quantum number, n, and applied electric field. In the presence of a Forster resonant field, sub-Poissonian distributions are measured. I next present a spectroscopic measurement of the energy level shift of a system of atoms which collectively shares two Rydberg excitations. The qualitative nature of the shift depends sensitively on the type of interactions between the atoms (van der Waals or dipole-dipole) and may be changed by changing the quantum state or applied electric field. This measurement provides the first spectroscopic proof that Rydberg excitation blockades are operative. Finally, I describe measurements of the probability for quantum state-changing and Penning-ionizing collisions to provide evidence for intrinsic, electric field-free-interaction resonances and complex many-body interactions in systems of cold Rydberg atoms.

Jan 1, 20082 citations

Dynamics of resonant energy transfer in a cold Rydberg gas

Sebastian Westermann, Thomas Amthor, A.L. de Oliveira +3 more

The European Physical Journal DJun 14, 200674 citations

Excitonlike exchange in two-photon transitions of pairs of cold Rb Rydberg atoms

Jeonghun Lee, Phatthamon Kongkhambut, Thomas F. Gallagher

We have observed an excitonlike exchange in two-photon microwave transitions between pairs of cold Rb Rydberg atoms, specifically, transitions in which a $n{s}_{1/2}n{s}_{1/2}$ pair undergoes the transition to the $n{p}_{1/2}n{p}_{3/2}$ and $n{p}_{3/2}n{p}_{1/2}$ states. This transition occurs due to the excitonlike $n{s}_{1/2}n{p}_{j}\ensuremath{\leftrightarrow}n{p}_{j}n{s}_{1/2}$ exchange in the intermediate states, and the process can be thought of as a F\"orster resonant energy transfer between Floquet, or dressed, states. In addition, the measurements provide clear evidence of the importance of the three-dimensional nature of the dipole-dipole interaction.We have observed an excitonlike exchange in two-photon microwave transitions between pairs of cold Rb Rydberg atoms, specifically, transitions in which a $n{s}_{1/2}n{s}_{1/2}$ pair undergoes the transition to the $n{p}_{1/2}n{p}_{3/2}$ and $n{p}_{3/2}n{p}_{1/2}$ states. This transition occurs due to the excitonlike $n{s}_{1/2}n{p}_{j}\ensuremath{\leftrightarrow}n{p}_{j}n{s}_{1/2}$ exchange in the intermediate states, and the process can be thought of as a F\"orster resonant energy transfer between Floquet, or dressed, states. In addition, the measurements provide clear evidence of the importance of the three-dimensional nature of the dipole-dipole interaction.

Physical Review ADec 26, 20173 citations

Resonant collisional energy transfer between Rydberg atoms

Thomas F. Gallagher

Physics ReportsJan 1, 199221 citations

We have observed an excitonlike exchange in two-photon microwave transitions between pairs of cold Rb Rydberg atoms, specifically, transitions in which a

n{s}_{1/2}n{s}_{1/2}

pair undergoes the transition to the

n{p}_{1/2}n{p}_{3/2}

and

n{p}_{3/2}n{p}_{1/2}

states. This transition occurs due to the excitonlike $n{s}_{1/2}n{p}_{j}\ensuremath{\leftrightarrow}n{p}_{j}n{s}_{1/2}$ exchange in the intermediate states, and the process can be thought of as a F\"orster resonant energy transfer between Floquet, or dressed, states. In addition, the measurements provide clear evidence of the importance of the three-dimensional nature of the dipole-dipole interaction.