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Haah cubic code

Haah's cubic code here means CSS Code 1 of the founding classification: a pair of data qubits occupies every vertex of a periodic cubic lattice, and one X-type plus one inversion-related Z-type corner pattern is translated over every cube. Its encoded dimension depends arithmetically on the periodic length rather than following one size-independent degeneracy formula. The no-string theorem excludes arbitrarily long nontrivial logical string segments of fixed width; it does not say that logical operators are absent, and it is not by itself a proof of thermodynamic self-correction. The orienting visual is explicitly a two-dimensional projection of the constructor's three-dimensional data, not a planar embedding.