The R?nyi entanglement entropy is calculated exactly for mode-partitioned isolated systems such as
the two-mode squeezed state and the multi-mode Silbey?Harris polaron ansatz state. Effective
thermodynamic descriptions of the correlated partitions are constructed to present quantum
information theory concepts in the language of thermodynamics. Boltzmann weights are obtained from
the entanglement spectrum by deriving the exact relationship between an effective temperature and
the physical entanglement parameters. The partition function of the resulting effective thermal
theory can be obtained directly from the single-copy entanglement.