Theory Group on Ultracold Atomic and Molecular Systems - Ultracold Rydberg Atoms
Their Allure
The large displacement of the Rydberg atoms' valence electron and its atomic core is responsible for its exaggerated response to external fields and, therewith, for their enormous polarizability. Rydberg atoms possess large dipole moments, gigantic extensions and, despite being electronically highly excited, they can possess lifetimes of the order of milliseconds. To take advantage of the susceptibility of Rydberg atoms to external fields, and in particular to other Rydberg atoms, ultracold Rydberg gases can be created. Starting from laser cooled atomic clouds, the atoms are excited using a laser tuned slightly below the ionization energy. The so created strongly interacting ultracold Rydberg gases are ideal candidates to study intriguing many-body physics and collective quantum phenomena on a macroscopic scale.What we do
Our goal is to provide tools to control and even stabilize these ultracold Rydberg gases. The essential precondition for realizing a controlled environment is the trapping of the atoms. Our findings suggest that trapped Rydberg atoms can be obtained by exciting the outermost electron of ultracold ground state atoms and capturing their collective atomic motion with one and the same trapping magnetic field configuration. We obtain our results considering the fully quantized states of the atom. To make computations feasible we adiabatically separate internal and external degrees of freedom.To illustrate our approach the following figure displays an example of adiabatic energy surfaces that are obtained integrating over the internal (electronic) degrees of freedom. These salad bowl shaped surfaces act as a potential for the center of mass motion of the atom.
[Figure: electronic adiabatic energy surfaces for a Rydberg atom in a magnetic Ioffe-Pritchard field configuration.]
The Rydberg states are quantized both with respect to their collective and electronic motion and we obtain a toolkit to tailor user-defined states by changing the degree of excitation of the electron and the parameters of the magnetic field. It is even feasible to pin down the core of the atom so that it can barely move without restraining the motion of the electron. This opens up the possibility to probe interactions between Rydberg atoms in a controlled way. Chains of so trapped atoms could even serve as a tool for quantum information processing making use of the state dependent atom-atom interaction.