Magic basis
= Magic basis
A <Bell basis> with <phases> chosen so that local special-unitary transformations of the two <qubits> are represented by real four-dimensional rotations. For one standard ordering it is $\Phi_+,i\Phi_-,i\Psi_+,\Psi_-$. Permuting these vectors changes generator conventions but preserves the invariant <concurrence> $|\sum_jb_j^2|$.<Entanglement of a Pair of Quantum Bits by Scott Hill and William K. Wootters>[Eqs.(3)–(6), phased Bell basis and concurrence]{ref}