Probing quantum coherence in ultrafast molecular processes: an ab initio approach to open quantum systems

TL;DR

This paper introduces an ab initio method for simulating ultrafast molecular processes that incorporates quantum coherence, relaxation, and dephasing, enabling the detection of quantum effects in molecules.

Contribution

The authors developed a novel simulation approach combining quantum chemistry with real-time stochastic Schrödinger equation to study molecular coherence dynamics.

Findings

Successfully reproduced experimental ultrafast spectroscopy results

Validated the method's ability to characterize quantum coherence

Demonstrated the approach's applicability to real molecular systems

Abstract

Revealing possible long-living coherence in ultrafast processes allows detecting genuine quantum mechanical effects in molecules. To investigate such effects from a quantum chemistry perspective, we have developed a method for simulating the time evolution of molecular systems, based on ab initio calculations that includes relaxation and environment-induced dephasing of the molecular wave function, whose rates are external parameters. The proposed approach combines a quantum chemistry description of the molecular target with a real-time propagation scheme within the time-dependent stochastic Schroedinger equation. Moreover, it allows a quantitative characterization of the state and dynamics coherence, through the l1-norm of coherence and the linear entropy, respectively. To test the approach, we have simulated femtosecond pulse-shaping ultrafast spectroscopy of terrylenediimide, a well studied fluorophore in single-molecule spectroscopy. Our approach is able to reproduce the experimental findings [R. Hildner et al.,Nature Phys., 7, 172 (2011)], confirming the usefulness of the approach and the correctness of the implementation.