  There exist zero-temperature states in quantum many-body systems that are
fully factorized, thereby possessing vanishing entanglement, and hence being of
no use as resource in quantum information processing tasks. Such states can
become useful for quantum protocols when the temperature of the system is
increased, and when the system is allowed to evolve under either the influence
of an external environment, or a closed unitary evolution driven by its own
Hamiltonian due to a sudden change in the system parameters. Using the
one-dimensional anisotropic XY model in a uniform and an alternating transverse
magnetic field, we show that entanglement of the thermal states, corresponding
to the factorization points in the space of the system parameters, revives once
or twice with increasing temperature. We also study the closed unitary
evolution of the quantum spin chain driven out of equilibrium when the external
magnetic fields are turned off, and show that considerable entanglement is
generated during the dynamics, when the initial state has vanishing
entanglement. Interestingly, we find that creation of entanglement for a pair
of spins is possible when the system is made open to an external heat bath,
interacting through that spin-pair having a repetitive quantum interaction.
