Real-time simulations of dissipative quantum dynamics

MACGIC-QUAPI dissipative quantum dynamics:

Systems of biological or technical relevance are often characterized by tremendous complexity, which leads to challenges for ab initio descriptions of the molecular dynamics. A way out is provided via a description in the system-bath formalism. However, situations in which the "slow" and structured protein environment leads to system-bath memory times of considerable length (non-Markovian memory) still pose extreme challenges to the description of such dissipative quantum dynamics.

We have developed a non-perturbative path integration method that allows to describe quantum dynamics subject to the coupling to a thermal bath [1]. The method, called MACGIC-QUAPI, is based on an intermediate coarse-grained representation of the quasi-adiabatic propagator path integral and provides a rigorous treatment of non-Markovian memory effects. The method exploits physical properties of the bath correlation function that allow for a non-equidistant, coarse-grained representation of the Feynman-Vernon influence functional and, thus, a decoupling of the total system bath memory time from the number of considered Feynman paths. The method makes long bath correlation times accessible. Due to the significant numerical speed-up, the method brings larger systems [2] and more complex environments [3] into reach and has great potential for simulations of biophysical processes.

Light-induced energy and charge transfer dynamics: 

Starting from ab initio descriptions of molecular Hamiltonians, we aim to describe dissipative quantum dynamics in complex biological environments. Examples are the exciton coupled charge transfer dynamics in a model of teh bacterial reaction centre B. Viridis [2] and the charge transfer dynamics initiated by photoexcitation of the FAD cofactor in the Photolyase / Cryptochrome superfamily [4,5].