There is an ongoing scientific debate about whether the quantum coherences observed in 2D electronic spectroscopy experiments on photosynthetic complexes — beginning with Fleming et al. in 2007 — are genuine long-lived electronic coherences or vibrational artefacts, and whether they are functionally relevant to energy transfer efficiency. This page takes no position on that debate.
What is not in dispute is the structural organisation of the light-harvesting apparatus itself. The light-harvesting complex (LHC) is hierarchical: antenna complexes absorb photons and transfer excitation energy to core complexes, which funnel it to the reaction centre. Each layer operates at a lower energy than the layer above. Energy moves directionally, downhill through discrete levels, in approximately 100 picoseconds from initial absorption to charge separation at the reaction centre. The overall quantum yield — the fraction of absorbed photons that result in a useful charge separation — is close to unity under physiological conditions. This efficiency is structural, not accidental. It is a property of the architecture, not of any particular quantum effect that may or may not be present within it.
The bilateral framework has a specific account of why this architecture is efficient. That account does not invoke quantum coherence, long-lived or otherwise. It invokes the three axioms. (This is not to say quantum coherence is absent; only that the efficiency does not depend on it.)
In the bilateral framework, every state is defined by its intersections with all others (Axiom A1: existence is relational). The excitation absorbed by an antenna chromophore is not localised on a single molecule the moment it is absorbed. It is immediately a distributed state — defined by the coupling of that chromophore to all others in the complex. This is not a quantum coherence claim. It is a structural claim: in a sufficiently coupled network, there is no such thing as a purely local excitation. In bilateral terms, a localised excitation is a classical approximation; the actual state is always the relational network. The state is the network, from the first moment.
The cascade through discrete energy levels maps onto the bilateral prime ladder. Observable scales cluster near prime-indexed rungs; energy flows from higher rungs (antenna, high energy) to lower rungs (reaction centre, low energy), with each transition a crossing event in which the ingress potential of one level becomes the egress record of the next. Axiom A3 — the present is the locus where future meets past, \(\tau\) monotonically increasing — means this flow is irreversible and directional by construction. The energy does not wander; it cascades. The direction is built into the axioms, not into the quantum mechanics of individual steps.
The near-unity quantum yield follows from bilateral completeness. In the bilateral framework, \(\hat{S}^\dagger\hat{S} = 1\): every crossing record that departs must arrive. An excitation that enters the bilateral mesh of the LHC must propagate to the reaction centre, because the mesh is complete and the \(\tau\)-flow is forward-only. Loss pathways — fluorescence, internal conversion — are not suppressed by quantum coherence; they are suppressed by the architecture of the mesh, which routes the excitation downhill faster than competing loss processes can act. The efficiency is kinetic and structural, which is exactly what the bilateral framework predicts.
The coherence debate has a specific structure: one side says long-lived electronic coherences assist energy transfer by quantum interference; the other side says the observed coherences are vibrational artefacts and that the transfer is essentially classical Förster hopping, made efficient by the downhill energy gradient and the network topology. The bilateral framework makes clear why both sides are partly right and why the debate, framed in those terms, misses the deeper point.
The efficiency does not require long-lived coherences. It requires a relational network (A1), a directional cascade (A3), and bilateral completeness (\(\hat{S}^\dagger\hat{S} = 1\)). These are properties of the architecture. Whether individual steps in the cascade involve quantum interference or classical hopping is a question about the mechanism of each crossing event — and the bilateral framework is indifferent to it, because the efficiency is a property of the mesh, not of the individual crossings. A Förster hop and a quantum-coherent transfer are both crossing events; both write egress records; both propagate the excitation forward in \(\tau\). The efficiency of the cascade is the same in either case, because it is determined by the structure of the mesh, not by the quantum mechanics of each step.
This is the bilateral resolution: the efficiency of photosynthesis is architectural. The debate about coherence is a debate about mechanism at the level of individual crossings — real and interesting, but not the source of the efficiency. Evolution did not optimise for quantum coherence. It optimised for the bilateral structure: a relational network, a downhill cascade, irreversible forward flow. The quantum effects, if real, are a consequence of that structure, not its cause.
Key references. G. S. Engel et al., "Evidence for wavelike energy transfer through quantum coherence in photosynthetic systems," Nature 446 (2007) 782–786. J. Cao et al., "Quantum biology revisited," Science Advances 6 (2020) eaaz4888 (review of the coherence debate). D. Low, "Infinity Zero: A Universal Synthesis of the Past, Present and Future," submitted to Foundations of Physics, April 2026 (ontologia.co.uk). Computational verification: github.com/dunstanlow/bilateral-mesh.