# Time-Dependent Open-Quantum Approach to Two-Dimensional Electronic Spectroscopy within a GW/BSE Active Space

## TL;DR

This paper introduces a new computational method to simulate 2D electronic spectra using quantum mechanics and realistic laser pulses.

## Contribution

A novel approach combining real-time propagation and GW/BSE for accurate 2DES simulations under realistic conditions.

## Key findings

- The method successfully captures stimulated emission and excited-state absorption in molecular systems.
- Coherence dynamics are observed as a function of population time with and without dephasing.
- Results align with experimental and theoretical data for benzene, chlorophyll b, and a benzene–phenol dimer.

## Abstract

In this work, we present a theoretical and computational
approach
that combines real-time propagation of the electronic wave function,
the GW/BSE formalism for the electronic structure of ground and excited
states, the theory of open quantum systems, and the phase-cycling
method to compute two-dimensional electronic spectra (2DES) of molecular
systems under realistic excitation conditions. The advantage of this
strategy is that it combines the accuracy of first-principle calculations
such as GW/BSE with an explicit description of the employed laser
pulses. This allows for better adherence to experimental setups. We
apply the proposed methodology to benzene, chlorophyll b, and a benzene–phenol dimer, also including
a pure electronic dephasing in the time propagation. The calculated
2DES maps reveal clear signatures of stimulated emission and excited-state
absorption, as well as coherence dynamics as a function of the population
time, both in the absence and presence of pure dephasing. Comparison
with experimental and theoretical published data has been carried
out, when available.