Orthogonal-basis invariance of a real Bell state
= Orthogonal-basis invariance of a real Bell state
For real orthogonal $U$, the Bell state $2^{-1/2}\sum_j|jj\rangle$ is invariant under $U\otimes U$ because $UU^T=I$.
= Orthogonal-basis invariance of a real Bell state
For real orthogonal $U$, the Bell state $2^{-1/2}\sum_j|jj\rangle$ is invariant under $U\otimes U$ because $UU^T=I$.