In Professor Koch's group there are two main topics under study: Quantum Chaology and Coherent Control. Our experiments on both of these topics using microwave ionization of hydrogen and helium Rydberg atoms helped make this method a paradigm for studying such problems in a real, driven physical system.

Kevin Schultz and John Wilson

Quantum Chaology: The boundary between quantal and classical physics is especially fascinating when classical chaos is involved. We investigate this boundary in two different kinds of experiments and interact closely with theorists. The ionization dynamics involves a subtle interplay of quantal and classical effects. Our recent work gets at higher-dimensional behavior by varying the polarization of the driving field or by superimposing collinear static and microwave fields. We have discovered striking, strong-field resonance phenomena.
Billiard systems are another workhorse for quantum chaology. We use electromagnetic waves (microwaves) in macroscopic, quasi-two-dimensional cavity resonators or other devices to simulate the behavior of deBroglie waves within and transported through mesoscopic enclosures (quantum billiards). Though semiclassical approaches for obtaining quantal properties often begin with classical periodic orbits, one must also account for effects that particularly interest us: ray-splitting, wave-tunneling, and wave-diffraction.
Coherent Control of Strongly-Driven Quantum Systems: Groups worldwide are developing general schemes for driving quantum systems preferentially toward desired outcomes by manipulating the amplitude-, frequency-, and polarization- and coherence-properties of electromagnetic field(s) driving them. Our research uses helium Rydberg atoms driven by strong microwave and other fields. Our recent experimental and theoretical work has focused on use of the relative phase in a bichromatic field as a parameter for strong-field quantum control.

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