Controlling Interactions and Optical Properties of Cold Rydberg Gases
Abstract: Electromagnetically induced transparency (EIT) is a quantum coherence phenomenon that causes a normally opaque medium to become transparent around a resonant frequency. EIT provides remarkable possibilities for nonlinear optics by enabling ultraslow group velocities and storage of light. The combination of EIT and interacting Rydberg atoms, which have large principal quantum numbers, has recently attracted considerable theoretical and experimental interest, as it holds promise for realizing extremely large nonlinearities by exploiting the exaggerated interactions between Rydberg atoms. I will present two many body approaches, quantum and classical, to describe interaction effects on the propagation of classical light pulse in an RydbergEIT medium. The nonlinear susceptibility shows good agreement between the two methods and experimental results and it is shown to exhibit a universal scaling behavior. I will also point out an analytical theory of the nonlinear response of cold Rydberg gases that yields simple expressions for the third order susceptibilities which are in excellent agreement with recent measurements. It is further found that the nonlinear susceptibility is not only drastically enhanced but also highly nonlocal in nature, corresponding to longrange photonphoton interactions.
I will further present our proposal of microwave dressing, that allows to modify the interactions between Rydberg atoms, and thereby control the optical properties of the gas. It is demonstrated that microwave dressing provides a powerful approach to control dipolar as well as van der Waals interactions and even permits us to turn them off entirely. In addition, the proposed scheme also opens up possibilities for engineering dominant threebody interactions.