  We study the quantum state transfer (QST) of a class of tight-bonding Bloch
electron systems with mirror symmetry by considering the mode entanglement.
Some rigorous results are obtained to reveal the intrinsic relationship between
the fidelity of QST and the mirror mode concurrence (MMC), which is defined to
measure the mode entanglement with a certain spatial symmetry and is just the
overlap of a proper wave function with its mirror image. A complementarity is
discovered as the maximum fidelity is accompanied by a minimum of MMC. And at
the instant, which is just half of the characteristic time required to
accomplish a perfect QST, the MMC can reach its maximum value one. A large
class of perfect QST models with a certain spectrum structure are discovered to
support our analytical results.
