Studies Involving Atoms in High Rydberg States

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In this project atoms in carefully engineered states that possess sizable internal energy, termed excited states, are used to study how atoms interact with one another together with the outcomes of such interactions. Atom-atom interactions, for example, lie at the very heart of many of the protocols proposed for quantum information processing and provide a novel means to probe phenomena such as magnetism and superconductivity. Laser beams are used to create excited atomic states whose physical characteristics, and hence interactions, are then manipulated using a carefully tailored series of pulsed electric fields. Use of such "designer atoms" enables atom-atom interactions to be probed in great detail and allows creation of novel chemical bonds and new molecular species. The laser-created atoms are large and lie at the interface between the microscopic word, characterized by quantum theory, and the larger classical world governed by Newton's Laws. This work provides a bridge between these two realms and helps illuminate the transition from quantum to classical behavior.Atoms in high-n Rydberg states are used to study strongly-coupled Rydberg systems, to generate long-lived two-electron-excited "planetary atoms," and to explore the physical and chemical properties of ultralong-range Rydberg molecules which comprise a Rydberg atom in whose electron cloud are embedded one, or more, weakly-bound ground state atoms. The work involves high-n, n~200-400, strontium Rydberg atoms created in both hot atomic beams and in ultracold atom clouds using multiphoton laser excitation. Strongly interacting Rydberg systems are created by exploiting dipole blockade and focused laser beams to create two, or more, Rydberg atoms with well-defined initial separations. Their mutual interactions are then increased by exciting them to higher-lying states using protocols developed previously to engineer high-n states with pulsed electric fields. The time evolution of the product strongly coupled system is examined to explore energy interchange and to search for long-lived configurations where, due to their correlated motions, the excited electrons remain far apart. Planetary atoms are created by first placing the Rydberg electron in a near-circular orbit and then exciting the second inner valence electron to a high-lying state. Rydberg molecule formation is identified spectroscopically through shifts in their excitation spectra. Such shifts also illuminate their structure and properties. The present studies promise new insights into the behavior of strongly interacting few-body systems which form the basis for many protocols proposed for quantum information processing and, by extension, into the behavior of many-body systems where interactions give rise to a wide variety of phenomena fundamental to condensed matter physics. The work also furnishes information on physics in the ultra-fast ultra-intense regime and speaks to the engineering of low-lying atomic states using attosecond laser pulses.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.