Excitation Energy Transfer: Quantum Many-Body Problems in Biology

Excitation energy transfer (EET) constitutes the first process in natural and artificial photosynthesis.  In this stage, an exciton generated by an incident photon is transported to locations where further chemical reactions take can take place.  This transport is a purely quantum mechanical phenomenon that is heavily modulated through the vibrations of the chromophores themselves and the protein skeleton that holds the molecular aggregate in place.  This many-body nature makes simulations of EET an exceptionally challenging task.  I will demonstrate how real-time path integrals, especially in combination with tensor networks, allow for the non-perturbative incorporation of the full thermal vibronic effects.  A framework for analysing transport pathways based on coherences will also be discussed.  These methods can also be used to study a multitude of other processes in condensed phase.