  The fidelity and entanglement entropy in an antiferromagnetic-ferromagnetic
alternating Heisenberg chain are investigated by using the method of
density-matrix renormalization-group. The effect of anisotropy on fidelity and
entanglement entropy are investigated. The relations between fidelity,
entanglement entropy and quantum phase transition are analyzed. It is found
that the quantum phase transition point can be well characterized by both the
ground-state entropy and fidelity for large system.
