Quantum excitation transfer, entanglement, and coherence in a trimer of two-level systems at finite temperature

The excitation probabilities, concurrence, and relative entropy of coherence for an array of three coupled two-level systems are studied analytically and numerically at various temperatures. We determine the excitation probabilities for each site, the concurrence between the outer sites, and the relative entropy of coherence of the system for three energy configurations of the trimer and various temperatures. We find that a well configuration (i.e., negative detuning of the inner site) at all temperatures localizes the excitation on the inner site, while a barrier configuration (i.e., positive detuning of the inner site) causes the excitation to be localized on the outer sites. We determine the decay times for the probabilities, concurrence, and relative entropy of coherence for all energy configurations at each temperature. The barrier configuration creates the largest concurrence at zero temperature; however, we find that the uniform configuration is able to resist the loss of quantum coherence and entanglement at higher temperatures more so than any of the other configurations.