Short-Lived Quantum Coherence in Photosynthetic Exciton Transfer: 100–800 fs, Not Long-Lived — E8 Intelligence Research

FINDING: Quantum coherence in photosynthetic exciton transfer is a real, measured phenomenon — but the evidence supports wavelike energy transport over ~100–800 fs at cryogenic-to-ambient temperatures, not long-lived room-temperature coherence as initially claimed. MATH: - Exciton Hamiltonian (Frenkel, tight-binding): H = Σᵢ εᵢ|i⟩⟨i| + Σᵢⱼ Jᵢⱼ|i⟩⟨j|, where Jᵢⱼ is dipole–dipole coupling, J ∝ κ·μ²/r³ (κ = orientation factor, μ = transition dipole, r = chromophore separation). - Coherence lifetime τ_coh measured via 2D electronic spectroscopy; FMO complex: τ ≈ 300–660 fs at 77 K (Engel et al. 2007, Nature 446:782), revised to ~50–100 fs at 277 K (Duan et al. 2017, PNAS). - Energy transfer efficiency η ≈ 0.95–0.99 in reaction centers; quantum yield Φ ≈ 1 per absorbed photon. - Redfield/Förster rates: k_Förster ∝ (κ²μ⁴)/(τ_D r⁶ n⁴) — the r⁻⁶ law is the classical baseline against which coherent (r⁻³, wavelike) transport is contrasted. - Dephasing: ρ_ij(t) = ρ_ij(0)·exp(−t/τ_coh); environmen Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com