  Two qubit entanglement can be induced by a quantum data bus interacting with
them. In this paper, with the quantum spin chain in the transverse field as an
illustration of quantum data bus, we show that such induced entanglement can be
enhanced by the quantum phase transition (QPT) of the quantum data bus. We
consider two external spins simultaneously coupled to a transverse field Ising
chain. By adiabatically eliminating the degrees of the chain, the effective
coupling between these two spins are obtained. The matrix elements of the
effective Hamiltonian are expressed in terms of dynamical structure factor
(DSF) of the chain. The DSF is the Fourier transformation of the Green function
of Ising chain and can be calculated numerically by a method introduced in [O.
Derzhko, T. Krokhmalskii, Phys. Rev. B \textbf{56}, 11659 (1997)]. Since all
characteristics of QPT are embodied in the DSF, the dynamical evolution of the
two external spins displays singularity in the vicinity of the critical point.
