} \vert \psi_0 \rangle = \frac{\vert u_0\bb{\bm{p}} \rangle^{A} \otimes \vert u_0\bb{\bm{q}} \rangle^{B} - \vert u_0\bb{\bm{q}} \rangle^{A} \otimes \vert u_0\bb{\bm{p}} \rangle^{B}}{\sqrt{0}},$$ which