Geometric Unification of Quantum Mechanics and General Relativity on Complex Projective Space

We show that the geometric structure of quantum state space — CPⁿ with the Fubini-Study metric (K=4) — contains substantially more physics than previously recognized. From this single structure, we obtain: the Born rule as a geometric identity including at dim H = 2 where Gleason's theorem does not apply; the Standard Model gauge group SU (3) × SU (2) × U (1) from CPⁿ isometries and stabilizers; and the Weinberg angle sin²θW = 3/8 from SU (5) = Isom (CP⁴). The framework is checked against 61 numerical tests, all consistent. We validate experimentally on IBM Quantum hardware: the Bures (Riemannian) mean outperforms Euclidean averaging in quantum tomography, scaling from +0. 003% (1-qubit) to +1. 332% (3-qubit), providing direct evidence that state space curvature has measurable physical consequences.