Partial Hydrodynamic Representation of Quantum Molecular Dynamics

A hybrid method is proposed to propagate system-bath quantum dynamics that uses both basis functions and coupled quantum trajectories. In it, the bath is represented with an ensemble of Bohmian trajectories while the system degrees of freedom are accounted through reduced density matrices. By retaining the Hilbert space structure for the system, the method is able to capture interference processes that are challenging to describe in Bohmian dynamics due to singularities that these processes introduce in the quantum potential. By adopting quantum trajectories to represent the bath, the method beats the exponential scaling of computational cost with bath size. This combination makes the method suitable for large-scale ground and excited state fully quantum molecular dynamics simulations.

B. Gu and I. Franco, J. Chem. Phys. 146, 194104 (2017)