  We show that the quantum teleportation protocol is a powerful tool to study
quantum phase transitions (QPTs) at finite temperatures. We consider a pair of
spins from an infinite spin-1/2 chain (XXZ model) in equilibrium with a
reservoir at temperature T as the resource used by Alice and Bob to implement
the teleportation protocol. We show that the efficiency of this pair of spins
to teleport a qubit is drastically affected after we cross a quantum critical
point (QCP), even for high values of T. Also, we show that the present tool is
as sharp as quantum discord (QD) to spotlight a QCP, where QD is the best
finite T QCP detector known to date. Contrary to QD, however, we show that the
present tool is easier to compute theoretically and has a direct experimental
and operational meaning.
