Describing the ground state of quantum systems through statistical mechanics

► We present a statistical mechanics description to study the ground state of quantum systems. ► Averages for the complete system are calculated over the non-interacting energy levels. ► We study the Hubbard model for the case of two electrons in two sites. ► Also we treat the half-filled band on a one-dimensional lattice. ► We show that the form of the entropy depends on the specific system considered.