(GQR23) A Quantum-Coherent Vortex Engine Drives Water Splitting in Photosystem II.

Biological water oxidation in photosystem II (PSII) is the sole natural source of atmospheric O2, yet thephysical principle governing its multi-electron, multi-proton chemistry remains unresolved. Classical PCET andredox-cycle models fail to account for the ultrafast coherence signals, abrupt geometric bifurcations, and nearlyisoelectronic S-state intermediates observed experimentally. Here we show that the CaMn4O5 cluster hosts arotating quantum-coherent tunnelling mode whose geometric evolution drives water splitting. Time-dependentquantum dynamics computed over experimentally determined S-state structures (8F4C–K) reveal a coherencevortex: a rotating corridor of maximal Ca–Mn3 tunnelling whose orientation shifts from ∼0◦in S2 to a near-vertical configuration in early S3, collapses entirely during O2 release (8F4G–J), and re-emerges in a re-alignedform in late S3 (8F4K). The rotation, suppression and reactivation of this vortex correlate precisely with protonrelease, Mn–O–Mn curvature changes and product extrusion, establishing the OEC as a curvature–coherenceengine rather than a static redox machine. This framework resolves long-standing mechanistic contradictions inPSII and provides a blueprint for designing quantum-enhanced, bio-inspired water-oxidation catalysts.