Purifications for canonical ensembles -- matrix product state approximation and entanglement

Matrix product purifications (MPPs) are a very efficient tool for the simulation of strongly correlated quantum many-body systems at finite temperatures. It is straightforward to compute an MPP of a grand-canonical ensemble. In this talk, we present methods for the efficient computation of MPPs of canonical ensembles under utilization of symmetries. Furthermore, we discuss their entanglement properties and a scheme for the efficient evaluation of global quantum number distributions.\\[0.5em] Reference: T.\ Barthel, Phys.\ Rev.\ B \textbf{94}, 115157 (2016).