Invited
Quantifying the induction of coherence into thermal quantum systems

The density matrix of a system in a thermal quantum state resembles the most classical case. In the energy representation, it contains only information on its diagonal elements, expressing the fact that the probability to populate a state with energy E is given by the Boltzman distribution. Any supplementary information regarding phase relations between the states is erased by the sake of averaging of quantum fluctuations. Upon the interaction of material system in thermal equilibrium with light, a change in the populations could take place, and, in addition some of the coherence of the light could be embedded into the quantum material system. Subsequently the density matrix will contain non-diagonal correlations between the states, which are the coherence.
Many quantum phenomena and applications relay heavily on characters of the coherences.

Within the talk the quantification of the induction of maximum coherences into a thermal system will be manifested. This will be presented in three stages: (1) At first, a way to measure the property in general will be suggested, and the state with maximum coherence will be presented. (2) Then, the consequence of constraining the energy of the system will be discussed. (3) Finally, a model for defining a hierarchy among coherences will be presented, and some conclusions regarding the maximal coherences with respect to the different sub-levels will be drawn.