  In arXiv:1407.8203, we introduced the idea of s-sourcery, a general formalism
for building many-body quantum ground states using
renormalization-group-inspired quantum circuits. Here we define a generalized
notion of s-sourcery that applies to mixed states, and study its properties and
applicability. We prove a number of theorems establishing the prevalence of
mixed s-source fixed points. For our examples we focus on thermal states of
local Hamiltonians. Thermal double states (also called thermofield double
states) and the machinery of approximate conditional independence are used
heavily in the constructions.
