  Within the well-established optical response function formalism, a new
strategy with the central idea of employing the forward-backward stochastic
Schr\"{o}dinger equations in a segmented way to accurately obtain the
two-dimensional (2D) electronic spectrum is presented in this paper. Based on
the simple excitonically coupled dimer model system, the validity and
efficiency of the proposed schemes are demonstrated in detail, along with the
comparison against the deterministic hierarchy equations of motion and
perturbative second order time-convolutionless quantum master equations. In
addition, an important insight is provided in this paper that the
characteristic frequency of the overdamped environment is an extremely crucial
factor to regulate the lifetimes of the oscillating signals in 2D electronic
spectra and of quantum coherence features of system dynamics. It is worth
noting that the proposed scheme benefiting from its stochastic nature and
wavefunction framework and many other advantages of substantially reducing the
numerical cost, has a great potential to systematically investigate various
quantum effects observed in realistic large-scale natural and artificial
photosynthetic systems.
