Robust Excitonic Energy Transport in Photosynthetic FMO-Like Systems Emerges from a Finite High-Performance Parameter Region

The functional role of quantum coherence in photosynthetic energy transport remains actively debated, with prior studies alternately attributing enhanced efficiency to coherent dynamics, environmental noise, or predominantly incoherent mechanisms. A key limitation of existing work is its focus on individual Hamiltonians or narrowly tuned parameter regimes rather than the global structure of physically accessible parameter space. Here, we perform a large-scale computational landscape analysis of excitonic transport in Fenna–Matthews–Olson (FMO)-like systems by systematically sampling thousands of Hamiltonians with structured perturbations to site energies, inter-site couplings, and environmental interaction strengths. Using an open quantum systems framework, we jointly quantify transport efficiency, mean first-passage time, and integrated quantum coherence across the sampled ensemble. We find that coherence is sparse and highly heterogeneous, while transport efficiency is dominated by a low-performance regime with a long high-efficiency tail. No universal or monotonic relationship emerges between coherence and either efficiency or transport speed. Instead, efficient transport occupies a finite, contiguous high-performance region in parameter space spanning a range of coherence values and kinetic behaviors, indicating that optimal transport does not require maximal coherence or fine tuning. These results establish quantum coherence as a context-dependent dynamical resource and demonstrate that robust excitonic transport arises from the geometry of the Hamiltonian landscape rather than isolated optimal configurations. More broadly, this landscape-level perspective provides a unifying framework for interpreting conflicting observations in the literature and for understanding how functional quantum effects can persist in complex open quantum systems.