Physics Colloquium- Prof. Yong Chen
October 22, 2018 - 3:00pm to 4:00pm
Rm. 102 A & B
Interference is a characteristic wave phenomenon that played important roles in physics. For example, two-pathway interferometry is a simple and powerful technique used to establish the wave nature of light in electromagnetism, and that of particles in quantum physics. Such interferometers are typically constructed in the real space, involving two waves traveling along spatially separated paths before being recombined to interfere. On the other hand, quantum physics allows “waves” (of probability, i.e., wavefunctions) or “paths” to be defined in more general or abstract “spaces”. This opens many possibilities to use interferometry as a powerful “phase sensitive” tool to manipulate, measure or even create novel quantum matter. In this talk, I will describe our experimental demonstration of quantum matter interferometers where the interfering pathways are not in the real space, but in some “synthetic” spaces involving different (and spin-dependent) trajectories for the evolution of the quantum system. Our experiments are performed with a Bose-Einstein condensate (BEC) of ultracold (87Rb) atoms, a highly-tunable synthetic quantum matter. By coupling atoms’ spin (and momentum) quantum states with appropriate electromagnetic (optical and microwave/RF) fields, various “synthetic” spin-orbit coupling (SOC) as well as quantum superposition states can be engineered. We study and control the quantum transport and quantum chemistry in such a BEC with synthetic SOC, and demonstrate two-pathway interferometry in energy-momentum space (synthetic band structure) as well as in chemical reactions (photoassociation), respectively. Time permitting, I may also discuss our experimental realization of a BEC on a synthetic cylinder (where self-interference gives a topological bandstructure mimicking transport on a Mobius strip), and studies of the roles of many-body interactions in two colliding and interfering spin-orbit-coupled BEC. Our experimental system can be a rich playground to study physics of interests to AMO physics, quantum chemistry, condensed matter physics, and even high energy physics.
 A. Olson et al., “Tunable Landau-Zener transitions in a spin-orbit coupled Bose-Einstein condensate”, Phys. Rev. A. 90, 013616 (2014); “Stueckelberg interferometry using periodically driven spin-orbit-coupled Bose-Einstein condensates”, Phys. Rev. A. 95, 043623 (2017)
 D. Blasing et al., “Observation of Quantum Interference and Coherent Control in a Photo-Chemical Reaction”, Phys. Rev. Lett. 121, 073202 (2018)
 C. Li et al., “A Bose-Einstein Condensate on a Synthetic Hall Cylinder”, arXiv: 1809.02122