Pulses: Applications to Thz Field Detection and Decoherence

During the funding period, our primary research efforts have focused on the exploration and control of coherent time-dependent electronic interactions within and between atoms. Specifically, we have examined the response of ensembles of Rydberg atoms to each other and to externally applied THz radiation. By definition, one or more electrons in a Rydberg atom are highly excited, and reside in a state of large principal quantum number, n. Such electrons are extremely sensitive to electric fields due, for example, to neighboring atoms or external radiation at frequencies from DC to THz. The strong, long-range coupling between Rydberg atoms is at the core of some proposed quantum logic implementations, but these require control of coherent, entangling interactions between atoms. Our recent experiments have verified the controllability of resonant few-body dipole-dipole interactions in cold gases and demonstrated electronic coherence times which are comparable to the time-scales for relative atom motion and the spontaneous emission lifetime of the Rydberg states. These coherence times are one to two orders of magnitude longer than those suggested by previous measurements, improving the likelihood of successful quantum logic implementations in these systems. In addition, we have developed an ultra-fast, potentially single-shot detector of THz waveforms. The detector exploits the large polarizability and electric field sensitivity of Rydberg atoms and could enable the visualization of THz waveforms with sub-picosecond resolution over 100 picosecond intervals.