  A perfect quantum state transfer(QST) has been shown in an engineered spin
chain with "always-on interaction". Here, we consider a more realistic problem
for such a protocol, the quantum decoherence induced by a spatially distributed
environment, which is universally modeled as a bath of harmonic oscillators. By
making use of the irreducible tensor method in angular momentum theory, we
investigate the effect of decoherence on the efficiency of QST for both cases
at zero and finite temperatures. We not only show the generic exponential decay
of QST efficiency as the number of sites increase, but also find some
counterintuitive effect, the QST can be enhanced as temperature increase.
