Real local-unitary representation in the magic basis
= Real local-unitary representation in the magic basis
The <anti-Hermitian> generators of local <qubit> rotations become real <antisymmetric matrices> in the <magic basis>. Their exponentials preserve $b^{\mathsf T}b$, and hence its modulus and pure-state <concurrence>. A common <phase> changes that bilinear quantity by a <phase> but not its modulus.