The (3+3) spacetime framework 1 makes a structural claim about quantum computing of unusual sharpness: every qubit's Bloch sphere — photonic, NV-centre, semiconductor-spin, trapped-ion, transmon — is the same physical S² of the third time dimension t₃ (1 §17. 2). Quantum mechanics did not invent the Bloch sphere as a representation device; in (3+3), it discovered the S² of the compact dimension. The latitude ϑₙode = arccos (1/√3) = 54. 74° on this universal S² — the same magic angle as in nuclear magnetic resonance magic-angle spinning since 1958 4 — is therefore predicted to protect all qubits from leading-multipole noise channels with axial symmetry, with no platform-specific tuning. There is no free parameter; the framework either works for all platforms at exactly 54. 74°, or it fails universally. We work this out platform-by-platform via the Y₂, ₀ (ϑₙode) = 0 identity. Three Level-1 derivations apply where the dominant noise has rank-2 angular structure on the qubit Bloch sphere: photonic two-photon absorption (ηₙode ≈ 0. 03–0. 20, reviewing 2) ; NV-centre ¹³C dipolar coupling (predicted T₂ ≈ 1 s in natural-abundance diamond, eliminating the need for ¹²C isotopic purification) ; and Si: P donor-electron hyperfine coupling (predicted T₂ enhancement of 100–1000× in natural-abundance silicon, eliminating ²⁸Si purification). GaAs quantum dots are also Level-1 via second-order rank-2 dephasing variance (10–100× enhancement). Two Level-2 anchored cases — trapped-ion magnetic-field dephasing and superconducting transmon multi-channel noise — give a more modest factor-3 dephasing-variance suppression (√3 ≈ 1. 7× T₂ enhancement) by the same second-order mechanism. The progression Level 1 → Level 2 tracks the directness of the Y₂, ₀ coupling: from rank-2-exact dipolar tensors (NMR-canonical) to rank-2-emerging-from-rank-1-variance (the weakest cases). The platform-specific magnitudes vary by orders of magnitude; the latitude is the same 54. 74° everywhere. Three universal predictions follow with sharp falsifiability: (i) cross-platform universality of 54. 74° ± 0. 5° across all platforms with no platform-specific tuning; (ii) platform-specific T₂ enhancements ranging from 100–1000× (Si: P) to √3 ≈ 1. 7× (transmon) ; (iii) secondary magic-angle equivalence at 125. 26° = arccos (−1/√3), with the spin-up/down chirality assignment reversed. The single most decisive near-term experiment is the NMR-MAS antipodal-angle test of Prediction (iii) — a sharp binary outcome at the canonical NMR platform, feasible immediately in 2026 with existing solid-state NMR hardware. The 2026–2030 falsifiability timeline (§9. 2) gives year-by-year cross-platform consistency tests. Six engineering proposals leverage these results, including a Si: P donor processor in natural-abundance silicon at T₂ > 10⁵ × τgate — comfortably above the surface-code fault-tolerance threshold (§11), with a materials-cost saving of 10⁵–10⁶ relative to ²⁸Si-purified equivalents at the 10⁵-physical-qubit scale. The room-temperature fault-tolerance projection of §11 generalises 2 §9 to matter-based platforms as a Level-3 conditional argument; the strongest cases (NV-centre, Si: P) have plausible > 50% joint probability of meeting all four conditional dependencies. The implications go well beyond engineering: cross-platform magic-angle agreement at 54. 74° would mean that the universe's qubit-state space is one compact dimension shared by all qubit platforms, identified specifically as the t₃ S² of the (3+3) framework. The Bloch sphere — treated as a representation device since the 1940s — would turn out to be a real sphere in the cosmic structure. We invite the QC community to test these predictions; the framework either works for all platforms at 54. 74°, or it fails universally.
C. R. (René) de Haan (Thu,) studied this question.