Abstract

When a molecule absorbs light, it creates an exciton—a charge-neutral excitation often described as the bound state of an electron and a hole. Efficient operation of photosynthesis and organic photovoltaics relies on the transport of excitons. Recent experiments have found evidence for long-lived quantum coherence in exciton transport in photosynthetic systems, but the microscopic origin of these coherences is disputed. I will discuss a set of experimental methods to understand properties of exciton dynamics, including quantum process tomography (QPT)—which can fully characterize exciton transport even in the presence of decoherence and relaxation—and a simpler pump-probe technique to separate electronic from vibrational effects. I will describe how to perform both types of experiments on the single-exciton space of small organic systems using nonlinear ultrafast spectroscopy. I will discuss the first experimental demonstration of the QPT technique and ongoing work to realize the pump-probe technique.