  We study the harvesting of quantum and classical correlations from a hot
scalar field in a periodic cavity by a pair of spatially separated
oscillator-detectors. Specifically, we utilize non-perturbative and exact
(non-numerical) techniques to solve for the evolution of the detectors-field
system and then we examine how the entanglement, Gaussian quantum discord, and
mutual information obtained by the detectors change with the temperature of the
field. While (as expected) the harvested entanglement rapidly decays to zero as
temperature is increased, we find remarkably that both the mutual information
and the discord can actually be increased by multiple orders of magnitude via
increasing the temperature. We go on to explain this phenomenon by taking
advantage of the translational invariance of the field and use this to make
accurate predictions of the behavior of thermal amplification; by this we also
introduce a new perspective on field-correlation harvesting that we feel is
worthy of consideration in its own right. The thermal amplification of discord
harvesting represents an exciting prospect for discord-based quantum
computation, including its use in entanglement activation.
